Limecrete perimeter capillary break

[tvrulesme]

I have an old (1810) listed building which has some damp issues. In the kitchen where there is damp at the base of the internal walls there is a (added in the last 30 years) concrete slab. 

 

Buildings of this age have no DPC and as the concrete itself looks to be damp, my feeling is that the concrete slab meeting the solid brick walls are probably contributing to the problem. Reading on buildingconservation website:

 

https://www.buildingconservation.com/articles/solid-ground-floors/solid-ground-floors.htm

 

One of the suggestions is to use a limecrete perimeter around the slab. This provides the capillary break required, allowing the substrate to breathe and preventing the footings from drawing trapped moisture into the walls.

 

"A hybrid floor design with a modern slab isolated from the walls by a vapour permeable limecrete perimeter strip"

 

To me this sounds like a sensible and relatively un-invasive option. Just wondering people's thoughts on this? Has anyone ever heard of this being used with success/failure?

 

Modern DPC injection is out of the question so this sounds like a decent thing to try. 

 

 

[Roger440]

I considered doing this in my house, rather than pull up all the concrete.

 

In the end, i ripped it all up.

 

When we first moved in the damp was terrible. Room always at 90% plus humidity.

 

Started outside reducing the soil levels, then stopped the rain coming in chimney. That helpd a fair bit.

 

Since then, plaster all removed. This had the single biggest effect. Within 3 months, the walls were dry. I could drill into them and dust would appear. Previously it was a slurry.

 

But even then, you couls still see a darker patch at various points just above the floor.

 

4 months since the floor was removed, everything is totally dry. Walking across the bare earth floor creates dust. Humidity generally 65-75% .Lime crete goes down mid Jan

 

As this is the first time getting involved in a non DPC property, i was sceptical about the theories put forward.

 

Given where we are now, frankly, im amazed at the speed it dried itself out. Scarecly believable considering the state when we got it. The socket back boxes which are 600mm up from the floor had corrided away completely, they had been that damp for so long.

 

As above, causes were, concrete floor with plastic underneath, modern gypsum plaster and excess outside soil levels.

 

The thing is, every house is different, soil conditions, water levels all different, so you cant ever be 100% sure until its done.

 

But id say, bite the bullet, take it up. Bear in mind, that any remaing concrete will still act as a barrier pushing the moisture sideways, so the limecrete section will need to disperse all the moisture from the floor are, but through a reduced footprint. Plus of course you can then install underfloor heating.

 

 

 

Edited December 22, 2021 by Roger440

[tvrulesme]

2 hours ago, Roger440 said:

I considered doing this in my house, rather than pull up all the concrete.

 

In the end, i ripped it all up.

 

When we first moved in the damp was terrible. Room always at 90% plus humidity.

 

Started outside reducing the soil levels, then stopped the rain coming in chimney. That helpd a fair bit.

 

Since then, plaster all removed. This had the single biggest effect. Within 3 months, the walls were dry. I could drill into them and dust would appear. Previously it was a slurry.

 

But even then, you couls still see a darker patch at various points just above the floor.

 

4 months since the floor was removed, everything is totally dry. Walking across the bare earth floor creates dust. Humidity generally 65-75% .Lime crete goes down mid Jan

 

As this is the first time getting involved in a non DPC property, i was sceptical about the theories put forward.

 

Given where we are now, frankly, im amazed at the speed it dried itself out. Scarecly believable considering the state when we got it. The socket back boxes which are 600mm up from the floor had corrided away completely, they had been that damp for so long.

 

As above, causes were, concrete floor with plastic underneath, modern gypsum plaster and excess outside soil levels.

 

The thing is, every house is different, soil conditions, water levels all different, so you cant ever be 100% sure until its done.

 

But id say, bite the bullet, take it up. Bear in mind, that any remaing concrete will still act as a barrier pushing the moisture sideways, so the limecrete section will need to disperse all the moisture from the floor are, but through a reduced footprint. Plus of course you can then install underfloor heating.

 

 

 

Amazing level of detail and actually reads very much like my damp survey. To date we have listed building consent for exterior masonry paint removal with DOFF system, lowering ground levels and installation of French drains and replacing internal gypsum plaster with lime. 
 

Have to agree with your approach on the limecrete whole hog. I’d be gutted if I did half a job and got half the benefits. 
 

Just to ask, did you do 1 meter of plaster from the floor or rip it all out?

[Roger440]

15 hours ago, tvrulesme said:

Amazing level of detail and actually reads very much like my damp survey. To date we have listed building consent for exterior masonry paint removal with DOFF system, lowering ground levels and installation of French drains and replacing internal gypsum plaster with lime. 
 

Have to agree with your approach on the limecrete whole hog. I’d be gutted if I did half a job and got half the benefits. 
 

Just to ask, did you do 1 meter of plaster from the floor or rip it all out?

 

Took it all out. Trying to "blend" the plaster afterwards seems to generally be considered a bad idea. The lime is significantly thicker, and it will crack along the join. Also then allows you to use one of the lime based insulating products.

 

Ours isnt listed which obviously makes things easier.

 

Pics below as it stands today. As you can see, its had a chemical injection applied at some point. ABOVE the floor level. Which stopped precisely nothing. 

Edited December 23, 2021 by Roger440