Under floor concrete or not

[johndow]

Hi

Last year I had to replace the timber floor of our cottage due to dampness etc.
I replaced it with a new suspended floor insulated with Thermafleece ( suspended under ).
Before begining I was advised to put a layer of concrete under the floor, but decided not to for a variety of reasons, not least I wasn't convinced it would do anything worthwhile.
I have since been advised that Limecrete would have been the product to use and I should have done it.
Have I made a mistake?
Can anyone reassure me or make me feel worse?
Thanks

John

 

[Nemesis]

I have earth under my floorboards.

Why were you advised to put anything there at all?

Is it still damp?

 

[johndow]

Hi

I also have earth, slightly sloping toward the middle, and no
there is no sign of dampness....but we aren't finished yet.
It was suggested by a " green " builder that we should have
lined the earth with Limecrete.
At the time I was unaware of Limecrete ( although we have used lime throughout for re-pointing the rubble walls and plastering inside. )
The " expert " seemed quite sur of what she was saying, and I'm tired and unsure!

Thanks

John

 

[Nemesis]

Well it is better than concrete saving the planet wise, but I have no idea why it was suggested in this case if everything is dry! Yes point and plaster with it though. I assume you have air bricks also?

The Thermafleece sounds useful though, for insulation.

 

[johndow]

Hi

Yes, we have two air vents, which may not be enough ( I've been thinking of adding a couple more )

I don't know why it was suggested to be honest, it just seems to be the
thing to do!!?? Old property, damp, needs new floor = concrete it.
I obviously hope that I was right and that it is not required.
Thanks

John

 

[Nemesis]

Two should be fine to dissipate any damp if it's not obviously damp.

I see now - you were advised to lay limecrete instead of the wood.

I presume you have sound joists, not laid directly on the earth?

 

[johndow]

Hi

No, we have laid a wooden floor on wooden joists which is about 18"
off the ground.
The suggestion was that the concrete/limecrete should cover the ground and then the floor on top?

Sorry if it's not clear.

John

Way back it was your initial suggestion of Thermafleece for insulation!

 

[Nemesis]

Well I can't see why you would need to lay anything on the earth - sounds very odd to me! Our floor is earth, that's traditional. It's not normal to cover it.

The Thermafleece I think you should find useful though, should make the place much more cosy. It's something I wish we had done when relaying our wooden floors, but it wasn't really very common then to think about underfloor insulation.

Many people are doing it now.

 

[Mark]

it is standard practice now even with suspended floors to put a layer of concrete down on the ground underneath.

I've yet to see a good reason for this, its been suggested that it stops groundwater rising. (which just made me think that once water got in you would have a splendid internal pool)

 

[Nemesis]

Rising to where?

Madness!

 

[Gervase]

Stop worrying! Bare earth, well ventilated, is absolutely fine.

 

[johndow]

Hi

I didn't see the need at the time of repacing the floor, and still don't.
However it has become the norm in new builds as well as restorations. ( apparently) There again, we were advised to inject stuff into the rubble walls to give damp proofing.
I'm feeling better about the decision, unless ......

All comments welcome.

Thanks

 

[Nemesis]

Has it become the norm in restorations?

Says who?

And as for injecting the walls ... waste of cash.

 

[NT]

I'm guessing the idea of it is to safeguard against conditions of blocked void vents, which does occur sometimes. However as long as the void is vented there is really no need for a concrete capping.


NT

 

[piper]

We have a suspended timber floor over bare earth in the largest of our downstairs rooms (the others are tiled) and it's fine. The house is a large one which was divided in two (not very well) in 1950. Most of the house has solid thick rubble limestone walls. Our neighbour in the other half installs plastic windows for a living, and has replaced all the original windows of his half AND the original front door of the house with plastic, as well as all the gutters & facias on his half. He has a very "traditional" building trade attitude (I hope I can be confident he doesn't read this!). This year he has ripped out the wooden floor of his front room which adjoins our afore-mentioned downstairs room, laid plastic DPM, several inches of concrete and then new timber floor. Needless to say he is very pleased with his work, and tells me "there was damp" in the floor. I'm just waiting for his displaced damp to come through the wall into our room.
Just thought the company would be interested in a story about attitudes in "the real world" out there!

 

[Nemesis]

Depressing - and in a few year's time no doubt some poor punter will buy it and be asking for help here to rget rid of the damp and restore 'to its former glory'!

 

[NT]

Probably more likely to inject a dpc, and replace plaster with cement. Then at next sale, render the property, maybe reinject etc. I'd give it 30 years or so before anyone asks here.


NT