Damp in Cottage

[Callismichael]

I am about to put in an offer on a 1682 brick cottage. it has damp on some of the walls. I lifted the carpets and noticed that the floor looked like a concrete slab.

I have looked at various posts but none really point at concrete floors. I have noticed that the exterior looks to have been pointed with cement mortar. My plan was to repoint but I don't really want to be taking up the concrete slab as the cottage already needs a lot of work doing.

thank you in advance.

 

[MatthewC]

Hi there, welcome to the forum.

I'm not totally sure what you are asking in your post (NB your first few posts take a while to be visible as they are moderated). Only you can decide if you should buy it with that concrete slab floor, but yes, the concrete is almost certainly the cause of the damp walls. If the floor is left as is, the walls will always be damp. Don't think you can treat damp walls - you have to tackle the cause, not the symptom, on old buildings.

If you don't want to dig up the entire floor (as I did, but mine was just earth), some people have tackled the issue by digging just the two or three feet beside the wall, and laying a limecrete floor there. It's an option, and perhaps one of them will post somewhen to tell us if it worked. My limecrete floor was a lot of work but it was well worth it, and the only other advice I can give is that you should do it before you move in - it's quite messy and instrusive, and takes a fair while to go off.

Matthew

 

[88v8]

Hello and welcome.

We bought a cottage from 1620. Before moving in I realised there was damp in one room, caused by a concrete floor.
So out it had to come, unbudgeted in cost or time arrgh, and in went a limecrete floor.

If you google, you may find someone local who can work in limecrete. Where are you, or rather, where is the cottage?

Ivor

 

[malcolm]

Most of my floors are concrete, but all of the damp was caused by high ground levels on the other side of the walls, leaky gutters, leaky drains, waterproof materials and paints etc. Problems are fixed now and for me replacing the floors was not necessary. I have no damp proof membrane but dug a trench around the house and covered it with a grating so moisture trapped by the floors could evaporate away before it started going up the walls.

 

[Flyfisher]

Yes, I wouldn't Automatically assume a concrete floor has to be replaced as it will depend on other circumstances, as malcolm has described. Also, don't forget that a limecrete floor my well be breathable but that just means moisture can move through it, so ventilation is still an important issue.

One of our rooms has a pamment floor laid on earth. It used to be covered by a wooden floor but with no underfloor ventilation. The breathable pamments did their thing and allowed the ground to 'breathe' through with the result that the amp built up under the wooden floor, which eventually rotted away. Now that the floor is uncovered it is bone dry to the touch, but if we cover it with anything impermeable then the moisture builds up again. I imagine that a limecrete floor would behave in much the same way.

 

[88v8]

Yes, I wouldn't Automatically assume a concrete floor has to be replaced as it will depend on other circumstances, as malcolm has described. Also, don't forget that a limecrete floor my well be breathable but that just means moisture can move through it, so ventilation is still an important issue.

One of our rooms has a pamment floor laid on earth. It used to be covered by a wooden floor but with no underfloor ventilation. The breathable pamments did their thing and allowed the ground to 'breathe' through with the result that the amp built up under the wooden floor, which eventually rotted away. Now that the floor is uncovered it is bone dry to the touch, but if we cover it with anything impermeable then the moisture builds up again. I imagine that a limecrete floor would behave in much the same way.

Yes. There were also ground level issues, but in that room the concrete was a pretty clear culprit as the Gripperods had rotted.
Indeed, one cannot shut out the damp, it still percolates into the room.

As I write, the RH in the house is in the 70%s.
It's damp. That's how it is.
And of course we make it worse by breathing. I have thought about a system of mobile extractors and tubes, like a diver's helmet, but walking around with a tube attached to one's head might become irksome.

Ivor

 

[Flyfisher]

Well, people have always breathed so I'm not sure that's what makes things worse :wink:

More seriously though, you're absolutely right in saying "it's damp, that's how it is" and I'd say it's our modern addiction to fully heated houses that's the root of the problem. It's expensive to fully heat every room in a house, even those we barely occupy, and so this encourages all manner of alterations to hermetically seal period houses in an attempt to conserve all this expensive heat.

Such heating, of course, enables the air to carry even more moisture than cooler air and the reduction of ventilation just exacerbates the problem by trapping all this moisture inside the building. It's all a compromise and period properties are simply 'different' to modern ones. I'm certainly not denying that things such as concrete floors cannot cause their own problems ( e.g. by concentrating ground damp into the walls etc) but, for the benefit of the OP, I just wanted to make the point that replacing a concrete with a limecrete one will not suddenly eliminate ground damp, it will merely change its behaviour.

My basic understanding of things is that period properties were (usually) built without damp courses and relied on fairly abundant ventilation to perfectly adequately manage ground damp, whereas modern houses are built with damp courses specifically to prevent any incursion of damp, thus significantly reducing the need for ventilation as a damp control. Both approaches have their merits but problems arise when trying to impose modern methods on a period property.

 

[Callismichael]

Thank you very much for the replies. Very useful. We have now had an offer accepted on the cottage so were just waiting for the solicitor to do their part.

I will do some more investigating into whether the floor is creating any issues or not. It also looks as though certain parts of the wall has cement pointing. My plan is to hack all of this off. This may have to wait until next year though now as it could be autumn when we get the keys.

I tried a vinegar test with some mortar from the property. It did fizz but not foam but visually looking at it, and scratching it, it seemed pretty hard. the gable end of the wall is in ok condition, whether this is damage from the pointing or just general wear and tear to the building is unclear. Piccy attached.

 

[Callismichael]

Hello and welcome.

We bought a cottage from 1620. Before moving in I realised there was damp in one room, caused by a concrete floor.
So out it had to come, unbudgeted in cost or time arrgh, and in went a limecrete floor.

If you google, you may find someone local who can work in limecrete. Where are you, or rather, where is the cottage?

Ivor

Cottage is based in congleton. The plan is to have carpets down. Just concerned if I partly lime Crete the edges it won't make a big difference if I thin carpet (boat foam backed though)

 

[Zebra]

I'm not sure. That could be lime pointing. I can't see too well on my phone, but the style of it looks like it's been done with a churn brush, and not a modern pointing style like bucket-handle or weatherstruck . Lime can be hard, and it doesn't necessarily fizz like mad. Try the vinegar test on known lime pointing and the results are rather undramatic.
Rather than taking it out I'd see first whether it's actually causing you any problems.