Help! Cement outside, Gypsum inside, on 17c timberframe?

[Silas]

Ok people my friends are about to buy a 17thC timber frame cottage in a Cambridgeshire, they are stretching themselves to find the £350,000. They asked me to come and see the property, which I was pleased to do.

It’s your typical lobby entry 3 unit with central inglenook formerly thatched. They are particularly pleased because this old cottage has been renovated and they believe they wont have to do a thing, they have had a full structural survey that says everything is fine.

Well you guessed it the cottage has a modern cement composite tile roof. A weather shield painted cement render to the outside of the timber frame with dry lined gypsum plastered on the internal walls and plastic UPVC windows throughout.

I need true factual information about the future problems that can face this old cottage as I have been unable to convince them that the modern materials can cause problems, I don’t want to fall out with them (old friends) but they will not have the cash to replace the modern materials, so how long can a timber frame cottage survive with such unsympathetic refurbishment, Apparently it was fully renovated about 15yrs ago and has been well maintained ever since. I could not see anything particularly currently wrong with the cottage, I told them that the building would not be able to breath properly and that the modern materials can trap moister etc but they just didn’t seem to get it, I’m not an expert so I could not really push the points, I need to give them facts. If they do buy the place can they do anything to mitigate the problems? Can anyone help me how to advise them.

 

[middi]

The fact is that nearly all old cottages in that part of the world were "renovated" in the manner you described.

There is no reason for not buying, and if good care is taken to look after the existing materials it will last a very long time, albeit the lifespan of the building may be shortned somewhat.

If your friend becomes rich, he-she can take it all off and have fun restoring it to its original condition.

 

[Nemesis]

Is it listed?

 

[Penners]

The fact is that nearly all old cottages in that part of the world were "renovated" in the manner you described.

Including ours, largely.

I don't believe that this inappropriate "renovation" is necessarily an irrevocable death sentence for a building. If the house that your friends want to buy doesn't suffer from damp problems, then there's no reason to suppose that it is going to crumble to dust around them.

 

[Me!]

My Parents bought their C17 timber framed house 30 years ago from the builder who modernised it. He cement rendered the outside, gypsum plastered the inside and fitted proper (not injected) damp proof membranes and damp proof courses throughout. It is absolutely fine. Lack of breathability isn't a problem, because the damp never gets in to start with.

 

[Penners]

the damp never gets in to start with.

Wish I could say the same!

 

[Nemesis]

The problem start of course when it does, when the cement starts to crack...

 

[Me!]

The problem start of course when it does, when the cement starts to crack...

In the last 30 years, they have had one small section of render fall off and be replaced, but the rest hasn't cracked yet.

 

[Nemesis]

Well, that's nice, but eventually it usually does - small structural movements happen and the damp gets in and the water isn't kind to the timber.

 

[Stephen]

A difficult problem to advise on.

Ideally traditional materials should be used. The use of modern materials in the way you describe can accelerate the speed of degradation of the original fabric.

However, the actual problem depends on a number of factors - too many to go into much detail here, but here are some pointers.

If the frame was in sound condition when the cement render was applied it could be quite a few years (20 +) before the accelerated decay would be seen. That said if the render is not maintained and/or it cracks and water gets in problems could appear earlier.

If the frame was poor before work took place the materials could have exacerbated an existing problem.

If the property is poorly ventilated with nowhere for moist air to go there could be a hidden problem of interstitial condensation causing damage.

If the past works have caused moisture to be directed into the fabric (e.g. due to poorly considered damp proofing, etc), this could accelerate decay.

What your friend needs to appreciate is that there is potential for a problem, but that it is impossible to identify when such problems may appear without opening up. It is also impossible to quantify what work would then be necessary once a problem becomes manifest - sometimes it is very limited in extent and other times cement render has been removed to reveal no frame remaining behind - the render is 'structural'.

I do not know of any specific scientific studies as such, but my comments and observations come from 20 years of surveying such buildings and seeing the results of such materials having been used - and I admit that on some occasions (not often) the frame has been exposed with no sign of a problem even though the render had been on many years. I do know that Ian Pritchet undertook some basic tests a few years ago by comparing buildings he worked on and came to the conclusion that cement renders, etc tend to increase the rate of decay by perhaps as much as 10 times on average.

As a surveyor I suggest your friend's surveyor should have pointed out the inappropriateness of cement render, but gone on to say that there was no sign of a problem at present and it may be some years before replacement has to be contemplated, although without opening up the actual condition of the timbers could not be ascertained and therefore when such work would be necessary could not be ascertained either.

The other issue here is whether the works had appropriate consent if the building is listed. If not, the cement render may be only one of their worries!

 

[middi]

Nemesis is right, danger exists when unseen cracks gradually let in exessive moisture behind the cement therefore the rate of evaporation is not as rapid as it would be as intended in its original costruction.

Cement itself is not harmful to timber frame, exept that the timber moves and cement does not, hence noticeable cracks are inevitable in time.

Short of ripping it all off and starting again, the next best thing is to keep an eagle eye on maintenance . There will not be any disasters looming around the corner if cement render has been used in the past, especially if it has been looked after.

 

[Silas]

Hi All

Thanks for the replies so far. I am surprised how calm and balanced you have all been towards this poor cement covered placci windowed old cottage.

1st the cottage isn’t listed but it is in a conservation area. It dose look like the place has been well refurbished, I did have a good poke around for them. But as I told them I don’t know much about timber frame structures other than what I have read here about natural movement of the frame cracking the cement and potential damp ingress + concrete and cement get very cold in the winter and this can potentially cause interstitial condensation leading to possible mould, damp, timber rot or beetle infestation within the dry lining.

This is what I observed.
Outside. Too the left hand gable there was a fairly new lean too ship lap boarded shed with a pitched felt roof, above this the rest of the exsposed gable wall was crack free.

Too the back was a conservatory and a modern two-story extension, so the original structure appeared completely protected from the elements on this side.

Too the Right gable, is a 4ft gap between the cottage and its neighbour, a Victorian building, no cracks too this gable, the soil pipe and drains exit the wall here and the modern drain pipes were at ground level, I thought they had to be at least a couple of feet down?

Too the front I spotted two repaired cracks, one vertical ground to eves and one diagonal from the corner of a window to the ground. If you looked from the corner of the cottage down its length you could see a slight outward curve in the wall, historic movement I guess? There is a shingle path all around that looks like it would be well drained.

OK inside, Modern extension (a big kitchen and a bedroom) and conservatory on the back. Some exposed wall timbers, exposed ceiling timbers all were heavily wood beetle damaged, but it all appeared like historic past infestation (our ancestors must have been hardy souls, probably would have been a family of 10 plus in a typical cottage like this). The soul plate was completely covered in cement it may have been replaced but I couldn’t tell. The walls have spread a little so at some point in the past a steel tye has been put through the building where the cross beams have been cut. The survey said that a plate had been bolted to the frame to support the floor joist and boards on the front side of the cottage and upstairs the banana effect was evident in the floor.

The cottage has a lot of its charm intact on the inside with really nice back to back red brick fires one with a wood burner the other a dog and grate. It’s just a shame about the windows and the roof.

My friends have always had new builds up till now. They did get a full structural survey on the cottage but it was not by a period property specialist. The survey spotted all of the above but stated that ‘no current problems were apparent, however thorough regular maintenance of the structure was essential due to the age and nature of the building and the materials used.

 

[Penners]

"no current problems were apparent, however thorough regular maintenance of the structure was essential due to the age and nature of the building and the materials used."

Well, the surveyor may not have been a specialist in period buildings, but actually that sentence seems to sum up the situation quite succinctly.