Conserving External Timber War Memorials

Speakers: Clara Willett, Dale Perrin and Gordon MacDonald.

Clara Willett: Good afternoon, everyone, and welcome to today's Technical Tuesday webinar on conserving external timber wall memorials.

I'm Clara Willett, I'm a senior building conservation advisor at Historic England and I'm joined by our two timber experts, Dale Perrin and Gord MacDonald.

Dale Perrin: Hi, I'm Dale Perrin, a conservation carpenter and senior building conservation advisor at Historic England.

Gordon MacDonald: And hello, I'm Gordon MacDonald, a building conservator and carpenter with many years experience of conserving historic wooden buildings and wooden artefacts.

Clara Willett: Before we make a proper start, for those of you who are new to Technical Tuesday webinars, I'd just like to let you know a little bit about Historic England's technical conservation team. We're a group of technical specialists, including conservators, scientists and engineers, and we undertake research and provide advice and guidance on technical conservation issues.

The first link that Len's going to put into the chat room for you takes you to the main technical advice page on our website, where you can find all our technical advice. And she's going to put a second one in there as well, which will take you to this catalogue which you can see here, and that lists all our research reports and guidance documents, which can be downloaded for free. So she's going to put those links and I believe those links will be available at the end as well, so don't worry about capturing them now.

Also, you might like to know that we have a technical conservation newsletter and that's emailed out on the first Tuesday of every month. And this will let you know about new technical conservation guidance and publications and any forthcoming technical conservation training events like this.

Today we're focusing on outdoor war memorials made from timber. These include lychgates, shelters and Calvary crosses, many of which were erected after the First World War. And here you can see we've produced a range of resources to support the care of these war memorials. And these include an advice note which deals in general with their conservation, repair and management. You can see this on the right here.

And in addition, there is detailed technical advice on war memorials which are constructed from stone, metal and timber. And that's the subject of obviously, today's webinar. As you'll see, they are packed with practical information and there's a lot of relevant information that has also been presented in previous webinars. So we'd highly recommend that you look at part one and part two of the War Memorial webinar series. And we've also got videos as well as guidance.

We'd also like to take this opportunity to ask you about your role and Len is going to post another poll for you about what your involvement with war memorials is, and again, I'll give you a few moments to respond to that. That's great!

So it seems like a lot of you are working as a heritage professional, but we've got some great people who are just generally interested as well, so that's fantastic. I'll let you close the poll then, and then I'll hand over to Dale.

Dale Perrin: To begin, let me give you a brief overview of today's webinar. We'll start by exploring wood as a material with a focus on its properties and the common mechanisms of decay. From there we'll give you an overview of survey and assessment techniques and then examine the typical forms of deterioration observed in external timber war memorials.

Finally, we'll discuss appropriate approaches to maintenance and repair, and we hope to leave time for questions at the end, so please feel free to post them in the chat as we go along. This webinar will not focus on internal timber memorials or smaller commemorative objects like benches, plaques or grave markers. That said, many of the principles and approaches we'll be discussing today are equally applicable to their care and maintenance and repair.

So let's begin with wood itself, because understanding how timber war memorials age and how best to care for them starts with understanding the material. A tree has three main parts: the roots, trunk and crown. The roots anchor the tree and absorb water and nutrients from the soil. The trunk is the tree's structural core and acts as a two way transport system, carrying SAP between the roots and leaves while also storing food.

The crown, its branches, twigs and leaves is the tree's energy centre. Through photosynthesis, the leaves convert sunlight, water and carbon dioxide into glucose, which then becomes the building block for the natural polymers cellulose, hemicellulose and lignin that together form the hard fibrous tissue of the trunk and branches.

Wood cellulose fibres account for 45 to 60% of the wood's dry weight, providing tensile and bending strength. Hemicellulose cross links with cellulose contribute into flexibility and lignin, accounting for 25 to 35%, acts as a natural glue, binding the fibres and giving timber its compressive strength.

Wood also contains non structural organic compounds such as resins, tannins, fats and oils, collectively known as extractives. Although small in quantity, extractives influence colour, scent, durability and decay resistance. The alignment and variation of wood cells along the tree's axis give timber its grain strength and ability to transport water.

Importantly, this internal structure remains after the tree is felled and continues to influence how the timber behaves, leading to shrinkage, warping or decay, especially in exposed memorials. And Gord is going to tell us a little bit more about this.

Gordon MacDonald: Thanks Dale. So to understand timber behaviour it really helps to begin with a bit of wood anatomy or the anatomy of a tree. The outer bark is that familiar protective layer made of dead cells. It shields the tree from insects, animals, fire and frost. And beneath that lies the inner bark. And this is where the living tissue is. Below that is the cambium, a thin but very important zone where new cells are formed.

The cambium produces new inner bark to the outside and new sapwood to the inside. Each annual ring records the tree's growth, containing early and late wood that reflects the seasonal conditions of that year. Sapwood is the living light coloured band responsible for transporting water and nutrients. It's wet nutrient rich, highly attractive to fungi and insects. This is important for us as conservators of course, and in all tree species, whether hardwood or softwood. We need to remember that sapwood is vulnerable to decay both in life and after the tree is felled.

While standing, the trees natural defences help protect the sapwood. But once felled, these protections stop or at least slow, leaving the materials exposed to decay due to moisture, sugars and limited extractives. Further inward lies the heartwood. This is the non living core that forms most of a mature tree and from which the highest value timber is cut.

As sapwood ages, it stops conducting water and transitions to heartwood. During this process, nutrients are reabsorbed and transformed into the extractives that impregnate the cell walls and cavities, providing colour, scent and critically natural decay resistance. These extractives continue to provide protection after felling and significantly contribute to the timber's durability.

At the very centre of the tree is the pith. This is surrounded by several years of juvenile wood formed during the tree's early rapid growth. Juvenile wood has a different structure and chemistry from mature wood, typically being less dense and more prone to movement and this can lead to warping. For this reason sawyers often either remove it entirely and producing what we would call free of heart timber, or they encapsulate it and box it within the section producing boxed heart timber.

Dale Perrin: And when we talk about timber types we often divide them into hardwoods and softwoods. In traditional and historic construction. Familiar hardwoods such as oak and elm come from broadly deciduous trees and typically produce denser, harder timbers. Softwoods such as pine, larch and fir come from conifers and are generally lighter and less dense. However, these terms can be misleading. Hardwood angiosperms and softwood gymnosperms are botanical classifications and they do not reliably indicate how hard, soft or durable a timber will be.

Some softwoods, like you, are exceptionally hard and dense, while some hardwoods, such as balsa, are very soft. Because of this variation, species selection has always been an important part of good carpentry, joinery, outdoor construction. The best performers, balance, beauty, strength, workability and crucially for exposed structures, natural durability.

Most timber war memorials in England appear to be constructed of oak. However, in some rare cases, teak and softwoods have been used. But once a memorial has been painted or coated, identifying the species becomes even more difficult, as shown by this bus shelter in Maldon. There are in fact excellent examples of long lasting outdoor structures made from both hardwoods and softwoods. Either can perform well when the right timbers are selected and the detailing is appropriate. Good specification involves more than choosing the species. It also requires selecting timber in a way that limits the amount of vulnerable sapwood and deciding whether a section should be free of heart or boxed harp.

As Gord mentioned earlier, these decisions have a significant impact on how the wood will behave in outdoor conditions. With these principles in mind, the next step is to look at how timber behaves when exposed to the weather and why understanding these processes is essential when assessing deterioration and planning effective repairs to memorials.

Gordon MacDonald: Yeah, so it's most important that we understand that wood is hygroscopic. So this means it's continually absorbing and releasing moisture in response to changes in the surrounding air, always seeking an equilibrium state with its environment. So as moisture content rises, wood swells as moisture content falls, wood shrinks. These are natural movements within the wood, but in exposed memorials, they can lead to warping, splitting, sometimes the failure of joints or decay if not managed through good detailing, ongoing maintenance.

Understanding how wood responds to moisture is absolutely essential when assessing existing memorials and also when specifying replacement timbers. Every part of the tree, from sapwood and heartwood to grain orientation and section sizes, all of these will influence how the material is going to behave once it's out of the weather.

Clara Willett: The main types of external timber war memorials that you're likely to encounter are lychgates, shelters and Calvary crosses. Many of them were created after the First World War and are often influenced by the arts and craft movement.

Lychgates are typically oak framed structures marking the entrance to a churchyard. Historically, this is where pallbearer would rest the coffin before the priest led the procession into the grave. The word lich comes from the Old English for body. Many include a gate or a pair of gates, and their commemorative purpose can be easily overlooked without reading the inscriptions or the commemorative plaque.

Shelters usually feature a roof, partial walls and seating with a commemorative plaque or inscription. They appear in a variety of forms and locations, including in some cases bus shelter style structures as seen in the previous slide.

Calvary crosses and I'm sorry we've lost our picture of our Calvary cross, but you will see more. Calvary crosses consist of a Latin cross, often with a carved or cast figure of Christ, the corpus set on a stone base, and this is frequently three tiered to symbolise faith, hope and charity, and evoking the hill of Calvary, which is where Christ was crucified. Many are protected by a small pitch roofed, clad in a variety of materials, shingles, slates, tiles and other sheet materials.

So now we're just going to talk a little bit about heritage significance. We cover this more in detail in part one of the webinars series and the general technical. The general technical advice note which we've put a link to. LEN will put a link to part one webinar.

Timber War memorials combine tangible and intangible heritage. The craftsmanship and the materials reflect the physical legacy, while community stories and practices sustain their emotional and cultural meaning. Preserving these memorials is therefore more than the fabric. It's about protecting their role in community memory and their resonance in the collective conscience. Because of this significance, many memorials are designated, listed, scheduled or if they're within a churchyard, they will require a faculty.

So consents may be required before any work is carried out. And you should always seek advice from the relevant statutory authorities before beginning investigation or repairs.

Gordon MacDonald: I think this issue of intangible communal values is really important. It was quite a lively topic for us in preparing these notes. Intangible communal values really shape expectations. War memorials were created by communities to honour the human cost of conflict, and as a result, many veterans and descendants view their condition as a sign of respect.

As a result, some expect a very clean, well maintained appearance, rather than the weathered patina that we might value in other heritage contexts. And balancing conservation principles with community expectations can be challenging. With good communication, though, it's usually possible to find an approach that respects both the historic fabric and the sentiment.

Dale Perrin: And then, once a memorial's significance is understood, the next step is a thorough survey and assessment. Timber structures in exposed settings can deteriorate quickly, so regular inspections are essential. A detailed survey should be carried out every five years by a conservation accredited architect or surveyor, ideally forming part of a quinquennial inspection for churchyard sites.

Custodians should also complete annual condition cheques and record any changes with additional inspections, especially after severe weather. Historic England provides survey templates in the conservation, repair and management of war memorials, as we saw earlier and in the timber volume of the Practical Building Conservation series. Local communities often notice early signs of deterioration, but professional advice is crucial when repairs are needed.

Depending on the issue, this may involve a conservation accredited architect or surveyor, a structured engineer for emergency or temporary measures, or an accredited conservator to prepare a condition report and options. Appraisal reports should cover materials, structural and surface condition finishes, inscriptions and previous interventions before repairs begin. Thorough documentation and research are vital and careful planning at this stage supports better long term outcomes. Alongside a condition survey it could be beneficial to include historical research to establish who designed the memorial, what materials were used, how it has changed over time and what it means to the community. And this underpins informed decisions about its care and repair.

An environmental survey would identify both the external and internal climates and finally an ecological survey would identify if the structure is inhabited or visited by any protected wildlife or species such as lichens.

Gordon MacDonald: So the tools we use to survey timber war memorials are much the same as those we would use for wooden structures. The choice really depends on the user's experience, the questions that are being asked and also our confidence in the use of the various technologies that are available to us.

So alongside standard tools, a typical timber specific assessment toolkit might include a digital camera with a north arrow on the scale bar in frame. Moisture metres Pinless metres are favourite because they don't damage the wood surface. But these are expensive and they're also… they take experience to use them correctly. Metres designed for subsurface measurement are the most useful because they're less susceptible to seasonal variations and also to salts on the surface.

Resistance drilling is sometimes used to identify hidden defects or even to understand — better understand joinery details. Measuring and drawing tools there's really no replacing them. These could include a portable laser level, but will always include notebooks, sketch pads, tape measures and a flexible ruler, etc. Something for probing and prodding joinery assemblies to understand them better.

Paint sampling lead analysis kits — these can be very useful especially in the earliest parts of the assessment. Sometimes we will use data loggers to monitor environmental conditions, temperature and relative humidity. Most useful over multiple years or at least multiple seasons. And then there's a whole host of specialist survey equipment which we might choose. Everything from structure for motion or multi image photogrammetry, 3D laser scanning, either portable or terrestrial. And these are all used for accurate spatial recording.

And as I said, it really boils down to one's experience and comfort with the different tools. It's always necessary though, to have an awareness of required consents. And Clara mentioned this earlier before any intrusive work on a listed or scheduled memorial begins, even for assessment purposes. Back to you.

Clara Willett: Thanks! Let's now look at the common forms of deterioration in timber war memorials and what drives them. Beyond challenges such as timber selection, sapwood and pith, which can all contribute to decay, there are additional factors to consider.

Gordon MacDonald: So we keep coming back to moisture and this will be a recurring theme. Moisture is the main driver of deterioration in timber memorials. It leads to fungal decay, insect attack and structural movement. Sun, wind, rain, the surrounding vegetation. These create uneven weathering, damp conditions. So maintaining really good air circulation is absolutely critical to managing water.

Persistent moisture encourages the growth of moss, algae, lichens, and all of these can trap water and accelerate decay. Note that, and this is particularly important in this context, some lichens are legally protected and we need to take that into consideration as part of our assessment too.

Wood generally becomes vulnerable to decay at roughly 22% moisture content. I know 20% is the rule of thumb that we hear most commonly, but 22 is a comfortable number when we're measuring moisture content in buildings. Unfortunately, many timber war memorials place timber in direct contact with masonry, increasing the risk of trapped moisture slowing down drying. And would destroying fungi thrive in these conditions. And prevention of those fungi relies on limiting water sources and improving air flow, so turning off the tap and increasing air circulation.

Insects will often follow fungi decay. They exploit that softening of timber for food and habitat. And effective moisture management helps prevent both of these issues. But established infestations require a really careful case by case treatment and that needs to be, excuse me, species, specifically Brian Redout's book. If you haven't come across it, timber decay and buildings is a fabulous resource. And it's…. There's a link here as well. So let's look now at specific deterioration issues in external timber war memorials and some of the things that we can do about them. Dale.

Dale Perrin: Thanks, Gord!

So lychgates and shelters pose specific challenges. As open timber frame structures with few enclosing elements, they are highly exposed to weathering and require careful detailing to manage water and reduce decay. Without rainwater goods water can collect at junctions or sill beams, and timber set directly on masonry is especially prone to moisture retention. Roof coverings, joints and footings all need to shed water effectively. Many were community built after the war, sometimes during a period of declining traditional craftsmanship, resulting in structures that may be more fragile or less durable. This context should guide sensitive conservation.

Roofing materials often deteriorate first with aged shingles, missing tiles, corroded fixings or blocked rainwater goods. All can allow moisture ingress. Sill beams and roof plates are particularly vulnerable because they can trap moisture from splashback leaks, debris buildup or incompatible materials decay. Weakened timber can then compress under load, causing structural movement. Poor detailing, settlement or even inadequate footings can worsen misalignment, including dropped or binding gates, which then can lead to metal components such as hinges and latches deteriorating or corroding.

Gordon MacDonald: Yeah, I think cavalry courses are particularly vulnerable owing to their tall, slender form, the high centre of gravity, and this makes them prone to wind loading. Loose joints or weak fixings can lead to movement and even collapse. Base decay is quite common, especially where posts. Timber posts are socketed into masonry where moisture can accumulate.

Water trapping features such as exposed joints, carved details on the corpus can create microclimates where fungi decay can be accelerated. And that's also where we'll find insect activity. While small pitch roofs really offer an awful lot of protection, the exposed corpus is particularly susceptible to water traps, erosion of carved details, deterioration finishes. And these elements should be inspected regularly to ensure they're not introducing an additional structural stress.

Dale Perrin: And it's worthy of looking at previous repairs because they can also reveal valuable information. Some can be sympathetic and effective, and others, such as cementitious infills or moisture trapping coatings, can cause further harm. Understanding what was done, how and why is essential. And even flawed repairs may hold heritage value.

Clara Willett: Surface finishes also play a crucial role. Paint stains and gilding deteriorate. Sorry about that. Paint stains and gilding deteriorate over time, cracking, flaking or fading, which affects appearance and reduces protection and inscription legibility. Because inscriptions often carry the names of the fallen, maintaining their clarity is essential to preserving the memorial's purpose and its role in community remembrance.

Some war memorials may have been painted later, which alters the original design and can at times accelerate deterioration by trapping moisture or concealing earlier decay and repairs.

Gordon MacDonald: Okay, let's move on to addressing some of these issues. So to address these problems, we need to tackle the causes, the root causes, rather than just the symptoms. Routine maintenance and management is always our first and most cost effective line of defence helping prevent the minor issues from becoming major failures later and also allowing early signs of deterioration to become identified in a timely fashion.

The key is knowing which custodians can safely handle themselves and when specialists advice… Excuse me. The key to this is understanding what custodians can safely handle themselves and when to reach for specialist advice.

Regular care includes simple but essential actions like clearing leaf litter, soil buildup, ensuring rainwater and drain. Rainwater is draining away from the structure, cutting back overhanging vegetation and again this is to improve airflow and reduce moisture retention. We avoid the use of strimmers and lawnmowers close to memorials as obviously accidental impacts can cause quite severe and irreversible damage.

Keeping low level areas adjacent to timber war memorials is important that we keep them free. Free draining free of debris, vegetation and this all encourages good drainage and reduces fungal decay. Protective measures such as inspecting and renewing paint stains, other coatings, these are just all strategies again aimed at managing moisture preventing its ingress.

Clara Willett: And what about cleaning? We've mentioned the importance of removing moisture retaining vegetation, but what about surface soiling that could retain moisture and obscure details?

Gordon MacDonald: Yeah, so another – this is another hot topic. The thing with cleaning is that it needs to be gentle. Soft nylon brushes, sponges and warm water with a non ionic soap that's typically sufficient. And it's always wise to make a small test area before applying to the rest of the structure. Low pressure steam pressure washers, abrasive measures, you know, such as sanding, grinding, wire brushing or any harsh chemicals should really not be used and they can irreversibly damage the timber and especially decorative surfaces.

So the aim here is not to make the war memorial look new, but to safely remove the dirt, staining biological growth while maintaining a dignified and cared for appearance. And this is that fine line that we spoke about earlier. Striking a balance.

So because gentle cleaning is suitable for most situations, but painted surfaces, detailed decoration or friable timber surfaces can require a more specialist approach. And that's where we really do need to reach to external advice. Dale.

Dale Perrin: So once the decay and its causes are understood, repairs should be prioritised. Immediate faults such as structural instability or failing roof coverings come first as they pose risks to both the structure and public safety and when uncertain seek advice from a structured engineer with conservation accreditation.

Next come the repairs and maintenance that prevent moisture ingress. Decorative work including repainting or re-gilding should follow and requires specialist skills. Where multiple elements are affected. The significance of each component should guide, prepare priorities and funding decisions.

Gordon MacDonald: Temporary stabilisation sometimes needed to prevent further deterioration and this can be useful while we're seeking funding, securing materials and looking to that specialist advice. Measures such as propping scaffolding, temporary roof coverings or the careful removal of vulnerable components should follow conservation principles, of course. But providing support without causing harm is the goal here and this can be useful for giving us time to plan long term repairs.

Temporary measures can become semi permanent if a project stalls, so they should be monitored and in some cases doing enough… Doing nothing might be the right solution, particularly where the damage is historic and stable. So let's look at the principles of timber repair here.

Dale Perrin: Material compatibility is essential for any repair. Replacement timber should match the original species, grain orientation, density, moisture content to ensure compatible movement and a visually sympathetic repair.

Timber is supplied as green, air dried or kiln dried. Green timber is freshly felled with a high moisture content. Air dried timber is often preferred for memorial repairs seasoned naturally to around 15 to 20% moisture content at roughly 25 millimetres per year. Kiln dried timber is dried rapidly to 6 to 12% moisture content and is generally unsuitable for exterior repairs because it swells once exposed.

Using poorly matched timber can cause differential movement and stress on historic fabric. So we should always allow sufficient lead time to source suitable material and ensure all repair timber is free of sapwood, which is inherently non durable.

Gordon MacDonald: So permeability and moisture movement are really critical to historic timber structures. As we've said, because wood is hygroscopic, it's always absorbing and releasing moisture. Repair materials, finishes, adhesives, consolidants, all need to be compatible with the natural behaviour of the timber and should not create barriers that prevent moisture from escaping.

Minimal intervention and reversibility are key conservation principles. We should use the least invasive methods, retaining as much historic material as possible and as the Borough charter states, do as much as is necessary, but as little as possible to meet the aims of the intervention. Wherever possible, we choose reversible techniques. That way future conservators can firstly recognise and then also undo or improve upon the work. Dale.

Dale Perrin: Yes, sorry. Repair approaches must balance traditional and modern techniques. Traditional carpentry is vital for authenticity and compatibility, but timber to timber repairs can conflict with minimal intervention because sound material must sometimes be removed to form strong joints, such as scarf repairs to beams or carved corpus elements.

Again, careful design should retain as much significant material and detail as possible. An effective repair design also manages water movement. Joints should avoid creating ledges or traps and instead direct water away from vulnerable areas.

Gordon MacDonald: Yeah. So modern interventions and this might include discrete surface mounted metalwork like straps or clamps. These can reduce the need to remove historic material and in some cases provide temporary support. Concealed metalwork, such as flitch plates, can also provide really critical structural support, allowing weakened elements to be retained. In comparison, this type of intervention is deemed as permanent and in some cases, irreversible.

Metal choice depends on context. So mild steel is strong, economical, but it requires some form of corrosion protection. Usually that would be hot dipped galvanising stainless steel, you know, it gives us high durability in damp and exposed environments, but it comes at a greater cost or for visible small fixings. Alloys like silicon bronze, they can provide strength, corrosion resistance and sympathetic appearance. Whatever the metal we choose, components need to be compatible with each other and with the timber. All metalwork should be properly protected to prevent stain and corrosion harmful reactions. And detailing needs to be carefully done to avoid moisture traps or introducing new stress points.

Clara Willett: And what are our thoughts on consolidation of historic timber?

Dale Perrin: Consolidation with epoxy resins or synthetic fillers can be useful when other repair options are exhausted. And this is also another really hot topic within our discussions. Low viscosity resins can help retain fragile or decayed timber that might otherwise be lost, making them one tool among many. They must be used carefully with repairs tailored to the specific project.

Epoxy based repairs require skill and strict control of temperature and application to avoid staining, leaching or damage to adjacent surfaces. While effective in the short term, resins can create long term issues. Timber may fail before the much stronger resin and the impermeable bond can trap moisture and encourage decay. Chemical consolidation can stabilise wood that has been softened by insects or grass. But broader environmental factors, such as ongoing weather or water exposure, must be addressed first.

Gordon MacDonald: Another naturally occurring feature we often see in historic timber is the development of shakes and cheques. These are splits that form as the timber dries and shrinks, and they're often mistaken for structural cracks, which they are not. True cracking is the result of overloading and it's actually quite rare.

The cheques generally do not reduce the strength of wood, so free draining cheques, we usually would leave those unfilled. But those on upper surfaces or running through carved or detailed areas can admit water and accelerate the decay if we leave those untreated. Where treatments are necessary, repairs should be minimal and carried out by specialists. It's very challenging to make a good quality repair in a cheque.

Open cheques can be plugged with oakum, and that's a material that can be capped with Linseed oil, putty or haired lime mortar to create a permeable sacrificial seal. Proprietary wood fillers may be suitable for small surface defects, but they vary so much in appearance, flexibility, permeability and durability, they're not our first choice. And all of these products, of course, they need to be chosen quite carefully and should never be used to conceal a major defect or in place of a proper repair.

Clara Willett: And what about surface finishes on timber wall memorials?

Dale Perrin: In most cases, structural elements of timber wall memorials are left uncoated, as you can see in the slides, allowing durable hardwood such as oak to weather naturally to a silvery grey patina. And where no historic coating exists, applying new stains or oils is generally discouraged. If historic finishes are present, their reapplication should be assessed on a case by case basis, considering both appearance and performance.

For detailed elements such as unpainted carvings or inscriptions, microcrystalline wax or tung oil can be used, provided they are maintained regularly. Where incised inscriptions have lost their original paint or gilding, careful retouching may be appropriate to preserve legibility.

Oil based paints are best for outdoor use, and gilding should use genuine gold leaf of a minimum 23 carat. As imitation products oxidise and deteriorate quickly. Acrylic sheet covers should be avoided as they obscure inscriptions and retain moisture, potentially leading to further damage. And for any finish to perform effectively, the timber must be clean, dry and stable. Surfaces should be free from open joints, cheques or splits where water could enter and become trapped.

Proper preparation is essential to ensure the finish supports conservation rather than inadvertently contributing to further decay. If the type or history of finishes is unclear, specialist advice should be sought. A finishes analysis could help guide an appropriate and sensitive conservation approach.

Clara Willett: Thanks, Dale!

We'd just like to ask you, I think we've got time for one more poll and we'd like to ask you what issues have you faced or you've facing with external timber wall memorials? And there's some options there. So if you could just give us an idea, that would be so helpful for us. So again, I'll give you a few minutes just to do that and then I'll be able to close the poll and we can see what your thoughts are. That's really interesting. So, structural defects and finding practitioners or with the right skills to carry out repair which probably leads us quite nicely onto our last point, really.

Gordon MacDonald: Yeah. You know, we've talked about securing the right professionals for specification and it's very important. But so is choosing the right contractor to carry it out. Timber war memorials require skilled conservators and craftspeople with, you know, who have the necessary experience and judgement to deliver good quality repairs sensitively and effectively. The knowledge of a good craftsman is or craftsperson ensures that the interventions will respect both the material and the memorial significance. Long term care relies not just on the specification of appropriate materials and methods, but also on the continuity of the traditional craft skills that underpin high quality conservation.

Clara Willett: And how can we find out about these practitioners? Where can people go?

Dale Perrin: That's a really good question, Clara. The Institute of Conservation's Find A Conservator directory lists icon accredited conservators and it's a really great resource where you can search by specialism including timber and location. And it's one of the top resources for the professional accredited conservators. And also there's the SPAB technical helpline which also have records of local craftspeople.

Clara Willett: And as we've mentioned, Historic England has a range of resources on conserving war memorials. There's not only our guidance documents and webinar recordings, but also videos. I'd also like to direct you to War Memorials Trust who have a wealth of information on looking after war memorials, guidance on finding suitable practitioners as well as grants and funding.

So for information about war memorials there is also the War Memorials Online and the War Memorials Register. They're brilliant sources for images and updating condition of things. So I highly recommend you look at those. I think that brings us to the end of our presentation. Thank you so much, Dale and Gord. We've given you a lot of information. We've covered the types of external timber, warmer wheels, common defects and how to approach repairs and maintenance. And we hope it's given you a clearer understanding of how to care for these important structures.

We'd love to hear from you and if you've got any questions you'd like to put to us, then we're all ears. So please, I think we've got some questions that have come through during our talk that we can respond to.

Gordon MacDonald Thanks, Clara! Make the big reveal so you can, you can see who you're, who you're chatting with.

Clara Willett: I've got, I'm not at Stonehenge but you know, it makes a nice background. So we've had some questions in and obviously if people do have some more questions, please do put them in the chat. So yeah, we've got some questions here. Somebody asked about non ionic soap, which we answered Simparonic A7 is just one example of a non ionic soap that is…. That can be used. But there's some questions here. So we have a question here about what wood filler might be appropriate. Is that something Gord or Dale, you would like to comment on?

Gordon MacDonald: Yeah. So in our discussion, we talk about using fillers, and there are a range of them. There are no commercial fillers that I really like. I prefer to make my own. And I do that in just the way we described, which is to run oakum first as a backer and then to give a surface cover to that with a linseed putty or lime. And lime, I think in most circumstances, is the most sensitive, most effective. Dale, do you have a trick up your sleeve that is a product available?

Dale Perrin: I think that what I would add to that is sort of a case by case study of what filler would be appropriate to that context. Like we said we had, it could be lime mortar or it could be the oakum caulking. And they're all very relevant, but it would depend on what you're feeling and how. And if it's possible to fill with timber, as we saw, then in certain instances, whether it's a carved detail or a structural detail, then that would be a big consideration. So it would be difficult to pinpoint products, but it would come down case by case.

Gordon MacDonald: Yeah, fair enough.

Clara Willett: Do you want to….. So we have another question. With timberwar memorials exposed to environmental factors such as moisture, are there any thoughts given to use of vapour open paints such as linseed paint, opposed to modern water plaster paints or gloss paints? So I think that's….. Yeah, the sort of more modern vapour permeable as opposed to. Yeah, so the sort of….. Yeah, the more modern paints as well. Do you have any thoughts on those? You'd like to comment?

Dale Perrin: I would be happy to share. Yeah..

[Crosstalk]

Gordon MacDonald: Things to say about that.

Dale Perrin: Yeah, there is a lot to say. And I will mention that historic England are working on an external finishes guidance which is due to be released later this year, I think, so everyone will have to keep an eye out for that.

And when considering a finish, I think the most important thing to consider is the moisture that's already in the timber. And if the timber is appropriate or at a state where it can be finished as any coating, and whether it's linseed oil or a modern, modern paint finish will trap moisture to an extent that any finish cannot release it. So, yeah, that would be my comment on that. Gord, have you got….

Gordon MacDonald: Yeah, I just sort of add to that. So permeable, impermeable. Whatever the case, we're changing the behaviour of the timber we're applying it to. So as Dale says, it's really important to understand the moisture of the timber that we're applying these finishes on and to anticipate how they'll behave in the future. Permeable finishes, you know, we're really all in. It's total commitment if we go that way and it's very, very difficult to create a complete impermeable barrier. So the breathable finishes are always favourites, but we need to remember that what we call breathable, quote unquote, is, is not as breathable as raw or exposed wood.

Clara Willett: We've got quite a few questions about surface finishes and so I'm going to try and so we can hopefully get through as many of these question. So there is a question about is there ever a case for using an oil wax on naturally grade oak externally?

Gordon MacDonald: Yes, I would say that can be quite an effective treatment of carvings, embellishment, relief, cutting, you know, really quite useful in that case. But I'm talking about a selective application and the question might be, should we take raw material and then treat it? That really needs to be assessed case by case.

And as I said before, we need to remember that if we're going to do something new to an exterior wooden object, we have to be thinking about all of those surfaces that we can't see and can't reach and can't treat. So the timber behaviour. If you think about a structure as an organism, we can't fool ourselves by treating only the visible surfaces and thinking that we're, you know, we're treating the whole object. We won't be.

Clara Willett: Rob Strong has just asked about many, many of the structures are black. What is this finish other than a natural tannin of oak?

Gordon MacDonald: Dale, you want to take us?

Dale Perrin: Yeah, that could be a variety of issues and there's also been another on finishes in general. A research document on finishes, specifically coal tar. And it could be a fashion. At that point, it was very fashionable to paint timber black and it's not the best colour for timber as it can like increases heat buildup. Could be any, any variety of products, whether it's modern or historical.

So without doing paint analysis, that would be the best option to find out exactly what it is, like I say it is a difficult colour and it seems very fashionable. And that can also be relevant to areas or geographical positions within the country where that's relative as well. So I hope that's helped.

Clara Willett: Yeah. And historic photos can be really helpful to sort of see what. What was perhaps the original design and intention, because these are, as we said, these are additional surface coatings. Somebody's asked, I struggle with identification of timber, timber type or species without intrusive testing. Do you have any tips?

Gordon MacDonald: There's one that I struggle with the same thing and I'm supposed to know how to do this stuff, so when I'm unsure. There are some pretty good online resources now. The Wood Handbook and Wood Database have really excellent clear colour photographs and we're not looking at, you know, necessarily just the colour of the wood to be the giveaway. It's more to do with the feature of the grain and the organisation of the annular ring, etc. But there are some good resources. Understanding the species and correctly matching it is very important. So if you really are stumped in your analysis of a particular object, that is something that's worth getting a specialist advice on.

Dale Perrin: And I think, just to add that a difficulty that I've had in sort of a revelation in the last years, even you could have one species of tree and how they've grown, where they've grown, will change what you're looking at and how you identify it. So there's a lot more that comes into it and an added complexity which is very relevant with historic timber. Yeah.

Gordon MacDonald: And keep an eye out for previous repairs too, because sometimes you can have a mix of species, just like you can have a mix of finishes that build up over time. Some of these structures are over a century old and they've been repaired over time and those repairs have aged now as well.

Clara Willett: Great! All your questions. It's brilliant. All your questions now are coming through. So we've got some brilliant questions. We may not have time to deal with all these, but there is an email address which Len can let you have. So you can follow up with more questions. And if we aren't able to get to these questions now, we'll be able to get back to you in due course.

There's a question about how jet washing damages historic external timber. Besides removing the patina, I think because it's high pressure and often it's not very controllable. What I would direct you to is our guidance on cleaning war memorials. That will give you a lot of information about why pressure washers. We wouldn't generally recommend them. They are very…. For a commercial market and they are high pressured and they can cause a lot of damage. It's amazing to see what they can do when used inappropriately at stone timber interfaces.

Do you have a view on altering the interface to improve durability or reinstate as original and accept future deterioration? So I think this is perhaps, maybe it's say a calvary cross, that interface between the timber and the stone. I think the question is about would you improve sort of the design or the fixing to prevent future deterioration?

Dale Perrin: I think from looking at some really amazing examples that you can see on the War Memorials Trust website, and that's a great place to see what's already been done and what people have done, you'd have to take into consideration the loss of original material to be able to replace. As we spoke about timber to timber repairs, but there's also some really conservative repairs to consider with metalwork. And we've seen a couple, especially with calvary crosses with external metalwork plates and brackets that hold that — actually hold the cross above that point where moisture is present.

So that's not saying that that will be necessary or applicable in all situations, but there are other ways and depending on the repair and the damage, on a case by case study of looking at it, there are other methods to approach that. Yeah. Would you agree, Gord?

Gordon MacDonald: Yeah, 100%. Nicely said!

Clara Willett: Brilliant! Well, it's now one minute after two in our time zone. I think we'll have to draw it to a close.