Few events could do more to spark interest in the preservation of historic timber buildings in Yorkshire than the recent discovery of a new one.
Restoration work on a property in Wakefield recently had some cement based render removed and this revealed a timber framed structure with carved posts underneath, with experts believing this could be the remnant of the home of an affluent family dating back to Tudor times, a period when timber was highly popular as a home building material.
Wakefield City Council had been undertaking the project on 6-8 Silver Street as part of its High Street Heritage Action Zone initiative, when workers undertaking the building conservation work discovered the timber beneath.
The carved posts are characteristic of wealthy people’s homes in Tudor times and the timbers are now being examined by experts from Historic England. If it is confirmed to date from this period in the 15th century, it will make it the oldest known surviving timber building in Wakefield.
For anyone who has responsibility for preserving a timber framed house in Yorkshire, this discovery should provide the perfect example of what damage cement-based renders can do to timber buildings. The wooden structure has suffered in the last 70 years or so, now needing structural work to strengthen it before the new lime render can be applied between the panels.
Analysis was done on the existing render to find out what binders, grits and pozzolans were used in the mortar and an identical lime render was created. Matching the original render is important, not only for aesthetics but also for functionality, which is also true when creating mortars for pointing.
The results from analysis found that the render was made using only quicklime and animal fibres, which produces a hot lime mortar that is used for lime rendering.
The render is applied to reeds or laths woven between the panels of the timber structure. The use of porous brickwork bedded down with hot lime mortar was also used as a way to infill timber panels in the past. The brickwork was then rendered over and also limewashed.
This timber structure has stood the test of time and it is only due to the use of nonporous materials and lack of the correct maintenance that it became at risk.
Now, it is held together firmly thanks to the structural carpentry work undertaken and with the aid of a new application of lime render coated with a hot limewash. This is now drawing any unwanted moisture out to prevent rot, while also keeping out any bugs like woodworm or deathwatch beetles that might make a hearty meal of the timber.
As a result of the widespread use of this effective means of protection, many great Yorkshire timber buildings have survived a long time, such as the Merchant Adventurers’ Hall in York, which is over 660 years old.
The fact that there are so many timber buildings in Yorkshire dating back centuries shows that the lime render coating method worked in maintaining structural integrity and preventing rotting and decay. Sadly, not every timber building has been so fortunate, as sometimes the wrong methods can be used.
Concrete is an obvious example. It may be a convenient and ubiquitous building material in modern times, but it has the reverse effect of lime render. Instead of drawing the moisture out of the wood, the concrete traps the moisture in, which is what causes the wood to rot.
Similarly, modern paints and sealants can also cause harm because they act as barriers to the transfer of moisture. Any moisture in the wood simply has nowhere to go, so once again it is vulnerable to rot.
Many treatments are available for the types of rot you may find in your home but not all are necessary, so you should identify the cause and then fix the problems. Dry rot and wet rot are both types of different funguses that only attack damp timbers.
Wet rot is a term used to cover a number of fungus types and is usually caused by a leak when the moisture content in the timber rises above 50 per cent. The most common form of wet rot is coniophora puteana.
Wet rot, if left unattended, can spread and cause structural damage so it is essential to identify any causes of damp and correct them, once the area dries the rot will stop developing
Dry rot is a fungal decay known as serpula lacrymans. It occurs when timber reaches a moisture content above 20 per cent. This type of rot is the most damaging and destructive because it spreads across masonry and destroys all timber in its path. Dry rot is caused by airborne spores settling onto damp timbers.
The spores germinate and develop roots called hyphae, which spread and secrete enzymes into the wood that break down the biological polymers into smaller units such as monomers. The monomers are then absorbed by the mycelium, which covers the wood in a wool-like substance.
The fungus sucks the moisture out of the wood while digesting the nutrients within it leaving the timber structurally weakened, when it reaches its final stages it spreads by sprouting more spores to continue the cycle.
You don’t have to use chemicals when treating dry rot, as it can be done by locating the fungus and removing it from the timber, making sure to chop all of the fungus and decaying wood out. Once this is done, the timbers can then be repaired or replaced and treated with limewash to aid with the removal of moisture and also prevent bug infestations.