Hi I’m new to the forum I have recently moved into to a 19th century stone property which I’m hoping to restore sympathetically. However I think I’ve made my first mistake. I’ve let a builder talk me into laying a concrete floor. We have extended the kitchen into a stone outhouse. The house has no foundations and the outhouse external walls have in parts soil up against it. The builder has used a pond liner on the inner wall attached halfway up with a baton, dug the floor down, laid sand, 4” kingspan, DPM then concrete. For the first few days the pondliner was soaking wet, the original kitchen floor next to the outhouse which has quarry tiles was soaking wet. It’s drying out now but I’d welcome comments on whether this type of floor is going to create problems in the future and whether it should be replaced before we take the renovation further!
- Thread starter Melro
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stuart45
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A limecrete floor would normally be used in this situation. You really need a builder who really understands the best methods for working on this type of property.
Saying that I do know of some old cottages that don't seem to have problems with concrete floors, but these were put in years ago when the problems of this were not so well known. Having a pond liner half way up the wall as well is a moisture trap as the walls need to allow air and moisture to pass through to escape.
As you are just starting out on the work, you may as well do it right.
Saying that I do know of some old cottages that don't seem to have problems with concrete floors, but these were put in years ago when the problems of this were not so well known. Having a pond liner half way up the wall as well is a moisture trap as the walls need to allow air and moisture to pass through to escape.
As you are just starting out on the work, you may as well do it right.
To be honest, where possible we will be doing most of the work ourselves, It was just unfortunate that we employed someone to do the floor element but I’m now we are thinking we should start again and remove the concrete ? Before we go any further. I assume that if there is moisture, because the concrete and liner is not breathable , the moisture will be pushed to other parts of the building and cause longer term problems. Is Limecrete the only option?
I imagine the plastic dressed up the wall is just being held up there temporarily, and will be cut off flush with the top of the slab when the concrete has set.
Depending on the details, this needn't be a big problem. It's all about relationships between that membrane and walls, internal and external ground levels, other floors and so on. Do this mental exercise: imagine that there is a hose buried under the middle of the plastic, running continuously. Where is that water going to go? If you can answer that in a way which doesn't have it entering the wall above floor level, and in such a way that it can evaporate away at the same rate it appears, then you have no issue.
In fact, I'll be a little controversial here. This problem can be over-stated. I recently dug out the (1960s concrete) floor of my cottage, and the ground underneath was absolutely rock-solid bone-dry clay, so hard that I had to drench it before it was soft enough to even use a Kango on. A house on flat ground with a reasonable water table and properly functioning gutters and drains will tend to create a dry patch underneath, so the presence of a DPM has no deleterious effect. Now obviously many houses aren't built in these ideal situations, but if you can design things such that the local circumstances are as close to ideal as possible, your concrete and DPM issue might be no issue at all. Remember too that modern houses with DPMs and DPCs don't suffer damp issues in the way old houses without can. The difficulty arises when you combine the two different approaches, as you are doing. Best avoided, but not necessarily insurmountable.
BTW, I hope the sand was underneath the DPM, not above it. Its purpose is to protect the DPM from stones etc underneath.
Depending on the details, this needn't be a big problem. It's all about relationships between that membrane and walls, internal and external ground levels, other floors and so on. Do this mental exercise: imagine that there is a hose buried under the middle of the plastic, running continuously. Where is that water going to go? If you can answer that in a way which doesn't have it entering the wall above floor level, and in such a way that it can evaporate away at the same rate it appears, then you have no issue.
In fact, I'll be a little controversial here. This problem can be over-stated. I recently dug out the (1960s concrete) floor of my cottage, and the ground underneath was absolutely rock-solid bone-dry clay, so hard that I had to drench it before it was soft enough to even use a Kango on. A house on flat ground with a reasonable water table and properly functioning gutters and drains will tend to create a dry patch underneath, so the presence of a DPM has no deleterious effect. Now obviously many houses aren't built in these ideal situations, but if you can design things such that the local circumstances are as close to ideal as possible, your concrete and DPM issue might be no issue at all. Remember too that modern houses with DPMs and DPCs don't suffer damp issues in the way old houses without can. The difficulty arises when you combine the two different approaches, as you are doing. Best avoided, but not necessarily insurmountable.
BTW, I hope the sand was underneath the DPM, not above it. Its purpose is to protect the DPM from stones etc underneath.
Hi Mike
Thanks for your reply. The pond liner was attached to the wall when the floor had been dug out. It has been placed half way up the wall with a baton with a slight overhang onto the soil at the base. I think the idea is to leave this in place and a stud partition wall installed to cover the wall. On the floor sand was laid, followed by 4” Kingspan, a dpm layer was laid on top of the Kingspan, followed by concrete. I suppose my worry is that this room has in parts soil up against the external wall. To some extent we can remove some soil but in parts it is around 3/4 of the way up the exterior wall.
I suppose if I was to do the hose pipe test, currently the water would almost certainly migrate into the neighbouring room i.e. the kitchen. I say this because when the concrete was drying out the kitchen floor (currently quarry tiles sitting on soil) and the pond liner was soaking. Both are dry now though. Such a dilemma!
Thanks for your reply. The pond liner was attached to the wall when the floor had been dug out. It has been placed half way up the wall with a baton with a slight overhang onto the soil at the base. I think the idea is to leave this in place and a stud partition wall installed to cover the wall. On the floor sand was laid, followed by 4” Kingspan, a dpm layer was laid on top of the Kingspan, followed by concrete. I suppose my worry is that this room has in parts soil up against the external wall. To some extent we can remove some soil but in parts it is around 3/4 of the way up the exterior wall.
I suppose if I was to do the hose pipe test, currently the water would almost certainly migrate into the neighbouring room i.e. the kitchen. I say this because when the concrete was drying out the kitchen floor (currently quarry tiles sitting on soil) and the pond liner was soaking. Both are dry now though. Such a dilemma!
Abi Cott
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Mike has suggested a Very impartial way of judging the situation. Based on your experiences I would be looking at alternative solutions. If you can't change the walls and you experienced that level of moisture change I would be seriously looking at changing the solution
malcolm
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Melro said:
New member posts tend to go un-noticed on here until you get to 5 posts. It's not that we are ignoring you, just that posts need to be approved first and by the time that happens we don't see them.
I think you are doing a very bad thing. I have some early concrete floors as much of my house is early 20th century. They don't seem to cause much bother so long as they are above external ground levels. Like Mike said - water will go where it can so it can get out.
The builder will be thinking tanking halfway up the wall to keep the water out. They did the same with my kitchen maybe 20 years ago and I'm not convinced that it worked perfectly. Green mould is a bad look for a kitchen wall.
You will be setting yourself of a future owner up for a fail and a bigger job in the future. External ground levels always need to be lower than internal floor levels. http://www.the-salutation.co.uk/blog/cast-ironish-grating/ is one fix for that
Also waterproof materials like kingspan or concrete should only be used if you have an air ventilation plan to vent away the damp you will get.
It is better is you do your own research so you can tell the builder what to do. Otherwise they will mess it up as they are planning.
malcolm said:
I'd argue here, with my architect's hat on, that an owner shouldn't have to turn themselves into an expert on a subject they know nearly nothing about, when the simple solution is to employ an expert to do it for them. A suitable architect on a job like that would cost less than one cock-up, and would prevent these sorts of headaches. Instead of trying to find out how to do something on the internet, and then trying to persuade a grumpy builder to do it a way they don't want to do it, the architect would set out precisely how the job should be done, and most likely recommend 2 or 3 decent local builders able to do it well. I'm currently retained, for instance, to guide the re-roofing of a 600 year old building, and for a fee of a few hundred pounds I've probably saved the client £10,000 already........and without them having to go up the scaffold or put their head in the loft once. An architect friend of mine has just overseen a renovation of a 400 year old building, no extension or alteration, and has guided the builder through a series of serious and unforeseeable issues such that the job didn't use any of the contingency fund at all. If there had been no architect involved, there would have been a series of bodges, and the budget (and schedule) would have been blown to bits.
MatthewC
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Yes, but in the same way you need to know enough to be sure that the architect is suitable for the job.MikeG said:
For instance, the (then) architect for the local church (Grade 1 listed, built 1100 - 1485 in limestone) passed an unsolicited quotation from a builder on to the church council for consideration; this was to fit a chemical DPC in all the walls of the church! Happily they turned it down and the architect was sacked anyway for other issues.
MatthewC said:
You should look at the prospective architect's portfolio. Most have websites showing their projects (as it happens, I don't). If you see glass and steel boxes, or hospitals or blocks of flats, then maybe look elsewhere. You could always ask the SPAB for recommendations, or check out the AABC site, or the RIBA. Again, I am not on any of those lists.