Floor boards on concrete

[El Greyo]

Hello everyone

We have concrete floors downstairs in our 17th Century cottage which are not very nice and are very cold. We (well I) had thought of digging up and replacing with insulated limecrete as the best option. But that is a big undertaking, expensive and disruptive. Having lowered ground levels outside and installed a French drain, hopefully, touch wood, cross fingers, we have reduced damp and I don't think it's a problem at the moment - although I'm keeping an eye on it. So there may not be much advantage in installing a limecrete floor, particularly as footings are very shallow.

So I think, at least for the time being, we'll live with the concrete and we thought we might put some floorboards over it. But I think it would be wise to do so in a way that is non-permanent - in case we so need to look at the concrete in the future. It would also be good to put some insulation under the boards.

So what might be good ways to fix the boards securely but non-permanently?

 

[middi]

Screw roof battens to the floor 25 x 50mm ( 25mm being the thickness) at 600 mm centres and 450mm apart.
insulate with celotex or similar between the battens and seal against edges. Stretch breather membrane tight across top of battens.
Screw wooden floorboards at 45 deg angle through floorboard tongue onto battens ( countersink head ). Carry on untill finished.
Stain or polish floor to own choise a live happily ever after
If problems in future, reverse the process and unscrew everything without damage.

Middi

 

[El Greyo]

Thanks very much for a quick and clear response. When you say 600mm centres, is that the distance between screws along the battens?

The concrete isn't damp at the moment but it has been uncovered for the last two years and I don't know whether there might be a little moisture coming through it when covered. Would there be any benefit, or problems, in putting a damp proof membrane over the concrete? But, of course, how would one fix the battens without piecing the damp proof?

I like the idea of living happily ever after. I never realised that floorboards had such miraculous properties.

 

[middi]

Yes, 600mm is the distance which screws ( frame fixings raw plugs) should be fitted along the batten.

If you suspect damp may be coming through cement floor ( I find it a bit difficult to believe as cement itself is waterproof to a certain extend) , then you can lay a blackfelt membrane below the battens. I wouldnt worry too much about the transfere of moisture to the sidewalls as if there was a real problem the cement slab would transfere moisture to the sidewalls anyway.
Also do not concern yourself too much with pierceing the membrane when screwing down the battens, if you are concerened then squirt some silicon sealant into the drilled batten and when you push and hammer the frame fixing plug down it will create a seal.

Middi

 

[El Greyo]

Thanks very much for the advice. I really don't know whether damp will be a problem. I guess we could test it with a meter but if it showed it had low moisture that may be because it has been uncovered for a long time. But if it shows some damp, that may be because we've been plastering and have been spraying lime and hessian a lot. We'll see.

 

[Zebra]

You could try to find out whether there's moisture coming up through the slab by laying something impermeable on it now, and then lifting it in a month or two and seeing what it's like underneath? I tried using a rubber car mat. Can't remember the result now, slab's gone anyway, replaced with new one.

 

[El Greyo]

Good idea, thanks. I'll give it a go.