New floor and now getting damp issues!

[dllive]

Hi,
Im doing a complete renovation. The builders dug out the floor and put in concrete/insulation/screed. Since then Ive painted the walls. The paint is blotchy and I went round with a moisture-reader and the bottom 24 inches of all walls (including interior dividing walls) are damp! The upper walls are ok.
Whats happening? How can this be resolved?
Thanks

 

[^woody^]

You could wait 6 months for things to dry

 

[dllive]

Its been about 5 months since the put in the new floor; and 4 months since they plastered the walls. Given all the hot weather it should have all dried by now(?)

 

[wessex101]

Do the walls have a damp proof course? Did the new floor have a damp proof membrane and was it lapped with the wall DPC?

 

[dllive]

The new floor had a DPC, but the walls havnt. Is the damp being forced away from the floor with DPC to the walls!? Whats the solution?

 

[wessex101]

Install a damp proof course in the walls? What is the wall construction?

 

[dllive]

stone and cob

 

[wessex101]

OK, you cannot install a DPC then. You will need to tank the walls internally with a cavity drain membrane and replaster. Or dig up the floor and go back to having a damp floor and walls and live with it.

Might be worth investigating why there is so much ground water causing this damp and possibly install some drains to reduce it.

 

[^woody^]

Given all the hot weather it should have all dried by now(?)

And given the hot weather there should be no rising damp

 

[dllive]

Is tanking the walls an expensive job? Should the builder have factored this in when digging out the floor?

 

[wessex101]

Is tanking the walls an expensive job? Should the builder have factored this in when digging out the floor?

Yes quite expensive so you are better off investigating where the ground water is coming from first and possibly tackle that, unless the house is built on top of a spring?

Whether the builder should have factored it in depends entirely on what you instructed them to do. I assume you had damp floors but the walls appeared to be dry so replacing an old (possibly earth floor) in an old stone/cob house with a modern concrete floor was likely to cause an issue somewhere else. A specialist builder probably would have known that and advised accordingly but an average Bob the Builder probably not.

 

[Footsoldier888]

dllive the solution is to stop all the works and get a proper damp assessment from someone who understands cob. This guy Peter Ward would be a good starting point, I have never used him myself but he is an expert on damp.

https://www.heritage-consulting.org/about-us

Personally I think if you start tanking walls it could worsen the situation, the whole idea of cob olde worlde walls is they breathe and the damp evaporates out.

If you are using modern plaster on cob walls it will be trapping damp in, as will the wrong kind of paint. It could even be condensation getting trapped on the cold walls. Or the drains as has been said. Or perhaps water is penetrating in somewhere?

The thing you have to do with an old house is work with the damp, not fight it with modern treatments. You can see on youtube Peter Ward has been called to houses where the walls are literally sopping wet, often caused by concrete render.

The good news is the solution is nearly always inexpensive, it's finding the cause that is the harder bit. Good luck with it anyway.

 

[dllive]

I mispoke - the walls are actually stone. (the ground floor walls are stone but upstairs are cob). Im not sure if that makes matter easier/better.

The walls were plastered with lime plaster - so atleast theyre breathable.

These walls were not damp until this floor was dug out and laid. So Im working on the assumption that the damp is spreading away from the floor's DPC and into the walls.
The builder is saying they should dry out once I get the under floor heating on (which will be monday). But thats not going to cure the problem!

I read this article: https://www.homebuilding.co.uk/how-to-deal-with-damp/#dpc which echoes what Footsoldier888 says ("work with the damp" and "not fight it with modern treatments" etc...).

Im heartened to hear "The good news is the solution is nearly always inexpensive" although would be surprised if thats the case. It seems anything building-related is very expensive!

But Im not happy that there wasnt a problem... then paid a lot of money for a construction company to put a new floor in... and now I have a damp problem!
Ill try and post some photos shortly.

 

[lostinthelight]

The new floor had a DPC, but the walls havnt. Is the damp being forced away from the floor with DPC to the walls!? Whats the solution?

I have flags on top of earth with stone walls and looked into DPM and concrete but Ty-Mawr Lime advised on using foamed glass and limecrete which would act as dpm but not force damp into the walls

 

[Footsoldier888]

If the windows haven't been open the evaporation out of the concrete may be hitting the colder stone and turning into water. Heat and ventilation is what you need in a situation like this.

I doubt the problem is major. A damp wall can dry out rapidly provided it is exposed to the air. However when you say you painted the walls, were they drylined or plastered first? It is very important to use the right paint too. If you are using masonry paint on bare stone that would not be the right thing as it will trap moisture in the wall.

A bit more detail or a photo will help.