Damp patch concrete floor

[Mac]

Hello
200 year old cob & stone cottage in Cornwall.

Adjacent Internal Back wall recently lime insulating rendered, lovely stuff.

Damp patch on concrete floor which has always been evident is now more evident!

Any suggestions please to remedy before laying new carpet.

Many thanks
Ben

 

[erikwoolf]

What is outside that door?

 

[Mac]

Under stairs cupboard!
All dry

 

[a twig]

Sorry for asking the obvious question but presume it is actually damp and not just old staining?

I only ask because I spilt some chainsaw oil on my concrete garage floor and it looks just like that

 

[Mac]

No it's almost wet to touch.

 

[a twig]

From what you’ve said it looks like it can be only coming from underneath - short of cutting out that section to take a look I’m not sure what else to suggest

 

[malcolm]

What was the floor covering before? Presumably something waterproof. If water wants to come through then let it out so the floor can dry and stop smelling damp. There won't be much water as concrete is slow to pass water through. A breathable underlay and breathable carpet should do the trick and the floor should dry in a year or three.

If the house is cob and stone the walls would like to be breathable too.

 

[Lacan07]

Hello
200 year old cob & stone cottage in Cornwall.

Adjacent Internal Back wall recently lime insulating rendered, lovely stuff.

Damp patch on concrete floor which has always been evident is now more evident!

Any suggestions please to remedy before laying new carpet.

Many thanks
Ben

View attachment 11414

could it be moisture in the lime plaster migrating down the wall and into the floor? that patch could be a weak spot in the concrete where the moisture is able to be released.

 

[Mac]

could it be moisture in the lime plaster migrating down the wall and into the floor? that patch could be a weak spot in the concrete where the moisture is able to be released.

Yes good point it could be. Plenty of water applied to cob and in the lime plaster. It was apparent before we did the work on the wall though.

 

[Lacan07]

Yes good point it could be. Plenty of water applied to cob and in the lime plaster. It was apparent before we did the work on the wall though.

Yes, that is odd, but as I said that patch could be a weak spot in the concrete where the moisture beneath is able to congregate and rise. We do occasionally see mysterious patches in the middle of concrete floors which suggest some kind of failure. I'm no fan of concrete floors at all but unfortunately its considerable amount of work to remove them.

 

[Mac]

Yes thank you I've had enough of considerable amounts of work following the replacement of cement plaster with lime recently!!

 

[Lacan07]

Yes thank you I've had enough of considerable amounts of work following the replacement of cement plaster with lime recently!!

Yeah, thats the problem with old properties, the list of jobs to undo the damage is endless and something that never occurs to estate agents or surveyors.

 

[Mac]

Yes for me it's weighing up the necessary work as opposed to the "we can live with that work" and to stop myself ever thinking it'll be perfect!

 

[stuart45]

When you see the labourers on site putting holes in the DPM to let out the rainwater before the concrete arrives you can see why some floors have damp issues.