Short answer: It wasn’t repaired correctly. It had repairs carried out, yes, but these repairs used the wrong mterials so made the conditions much worse. Moisture was reaching vulnerable timber, while cement pointing, filled joints and the internal blockwork complicated drying and concealed deterioration.
The building and the problem
This was a 17th century timber box-framed building, not that old but important as it related to the nearby church. It has a modern extension to the rear which was designed by a conservation architect but it appears there was insufficient funds to remedy the very many issues affecting the original house.
What I found
- The roof had Pennywort growing in every joint and this had rooted through and below tiles and was growing up inside timber cladding.
Pennywort behind timber cladding of a dormer window
The pennywort is simply a symptom of poor recent maintenance. Removing or discouraging moss on the roof will have prevented its growth but surroundung trees close to the roof were always going to make maintenance onerous.
- The stone base of the walls were pointed using cement so there was no evaporation of moisture which was then able to be absorbed into the timber.
Wet rot exposed behind cement on the stone plinth
Cement has its places in old buildings but not where moisture may be expected as it prevents efficient evaporation. This is a common cause of dampness in old houses which is bad enough, but it causes timber frames to rot. The cuboidal cracking is indicative of wet rot.
- The timber frame above had been repaired with cement and silicone sealant then painted so any moisture it contained continued to cause the frame to decay unseen.
Numerous areas had evidence of filler being used, all joints – these are generally more vulnerable due to the various gaps the joints have – have been filled, some natural splits and shakes had been filled and the result was that the timber around these was in much poorer condition consequently requiring a greater level of repairs and more expense.
- Internally was the biggest surprise. Clearly the dampness had been a problem so the solution they used was to build concrete block walls inside against the timber frame. This made the frame rot much faster.
This thermal image does not show the timber elements. Different materials deal with heat loss differently but this is homogenous to the frame is concealed
The problem is that we generally don’t know where to get the correct information from. Everyone has an opinion, some of these may even be founded on some experience, but each property is different. One rule does not fit every building. I often read with despair Facebook groups giving advice to each other because something worked on their house. Different construction materials and methods, different site conditions, different combination of defects causing different syptoms, so it is impossible to diagnose remotely and it never, ever, has one single solution. Well, apart from ‘repair it properly!’
Why it happened?
Ill informed repairs using good, but incorrect, repair methods and materials. Every method of repair of this property was incorrect. Cement prevents evaporation and it is brittle so cracks easily against an ever moving timber frame the lets water in to become trapped. Silicone sealant likewise prevents evaporation of moisture and is used in the most vulnerable places – the joints. Gloss paint is then applied over the frame to prevent any evaporation and traps the rest of the moisture in.
What should be checked before specifying repairs?
The building need to be operating at its peak condition elsewhere for repairs to work correctly. An analogy would be wanting to put a bigger engine into a car to make it go faster but ignoring the flat tyres.
The roof needs to stop water ingress so the roof nees to be inspected, tiles, ridge, flashings, verge treatment; the gutters need to be clear and discharging to below ground pipework or at least away fro the house; walls need to allow evaporation of moisture. This is counter intuative but vital for any old building. Ensure evaporation is possible so identify any inappropriate materials, determine the causes of decay such as cement nortar, high ground levels etc. Get a proper survey – from us.
What I recommended and why
Surprisingly, our client still bought the house and was quite prepared for the significantly onerous task of dismantling it and restoring it to a sound and useable structure.
Recommendations included to remove any vegetation growing in and against the fabric, carefully remove any and all filler material from the timber frame, remove any cement from the frame and stone plinth, remove the concrete blockwork inside and allow the building to finally expel the moisture.
