Wood floor on concrete

[Redeye]

I'm shortly going to start work on our kitchen and dining room and hopefully make the thing work a bit better and look a little less rancid. The building itself is about 200 years old but was converted in the 20's and has had various bits of work done since so although there are some elements of it being a period property, it's more of an old evolved building than a period one.

Anyway, underneath the current hideous laminate flooring I'm pretty sure is a red painted (?) 1920's concrete floor. There's a small section of quarry tiles which are so small in area and so uneven that I'm planning on taking them out and expecting to reveal a similar concrete base.

I'm planning to put down oak flooring as the replacement as it seems to be not too out of place in the context of the house and generally fit in with what we're trying to achieve. The current concrete floor is quite uneven (not sure how bad yet) so may need some screeding first. I was then planning on putting a damp proof membrane onto the concrete, an 18mm layer of WBP plywood on top screwed down to the concrete, then secret nailing the oak boards on top (allowing expansion gaps, letting the wood acclimatise first etc). This method seems to be recommended in several places, along a similar one with battens instead of the plywood, although I'm worried that condensation on the cold floor underneath would warp the oak boards if I used battens.

Any thoughts/suggestions on my plans?

 

[Craig]

Worth considering gluing the boards down instead. I have done this twice - use Sika Bond over their insulated mat (which has slots cut into it for the glue). You get a "solid" floor which can be laid quite easily without screwing or nailing into the concrete. We laid a 20mm solid oak planking T&G floor onto a concrete floor in a basement - 9 months on and no warping.

http://www.chauncey.co.uk/floors/sikabond.htm

We used the sausages and the glue gun method.

 

[Redeye]

Thanks Craig.

I'd been warned against the glueing methods because of the potential warping problems, but in this situation it might help me with several other potential problems.

Anyone else got advice/experience with glueing wood floors onto concrete?

 

[CHRIS]

I laid a new oak floor over my front room but in one corner (2m x2m) next to the front door someone in the 60s poured a concrete slab, the rest of the floor is over a cellar approx 25m2.

The way we laid it was to secret nail using a porta nailer over the timber joists and when we came to the concrete area we used that wonder substance "Gripfill" and just stuck it down straight to the slab, the only problem is that when you walk on it with boots on it is noisy but it has never moved or warped (6inch boards) and is solid.

My friend has a modern apartment in E London and has had a new oak floor over concrete laid using the floating floor method with an underlay of some foam/dpm stuff and the t and gs being glued, the floor has a 10mm expansion gap around the edge filled with cork strips and the skirting covers that. You must have a very level base for this method and one of the self leveling compounds might be the answer (expensive, full of who knows what and messy). I know this is not in the period property mentality but as more and more people end up with concrete slab ground floors the floating floor will become quite normal. You have to use floor clamps to hold the t and g whilst glue dries doing this method.

 

[Roger H]

Hi Craig.

I screwed treated softwood battens (2"x1") to my existing concrete floor, and screwed (and plugged) t&g over that. Was straightforward, although I wish someone had told me you could buy bags of softwood plugs before I cored-out several hundred myself. I thought screws through the face of the boards might be more secure than nails through the tongue, if there was ever any movement in the floor. Seemed to work ok. Floor was very dry so didn't think condensation would be an issue.

Roger.

 

[Nemesis]

I wish someone had told me you could buy bags of softwood plugs before I cored-out several hundred myself.

Well you should have asked...

 

[Andrew Bodenham]

I was faced with the same problem in our kitchen / dining refurb. The 1980's concrete floor was sound and dry, but very uneven. I didn't want to raise the floor level too much, as this would cause problems with doorways and adjoining rooms, so that ruled out battens and boards.

Eventually I levelled out the worst excesses of the concrete with Sika 5N levelling compound, before laying 12mm ply over to form a smooth sub-floor. A 3mm neoprene / PE underlay was used under the ply to reduce noise, even out small irregularities and provide a little insulation. The ply was screwed to the concrete at 400mm centres with multi-monti screws (Screwfix). These go straight into a 5mm hole without the need for a plastic plug - excellent!

To keep the overall thickness down I used 10mm thick overlay oak flooring, t&g all round. This was attached to the ply with a run of PU glue along each plank, then pinned in place through the tongue with an 18g air-nailer to hold it whilst the glue went off. A belt-and-braces approach, but relatively quick, very solid, and coped well with the smooth-but-not-completely-flat nature of the floor.

I machined some 11mm thick oak to make door thresholds and to trim around a slate hearth. Again these were glued and pinned in place. Two coats of Osmo Polyx were applied after light sanding. The end result looks great and has performed well so far.

 

[Ushy M]

[A 3mm neoprene / PE underlay was used under the ply to reduce noise, even out small irregularities and provide a little insulationquote][/quote]

Andrew, very interested to know what this underlay is and where we might be able to get it - we're thinking of a similar approach in one of our downstairs rooms where we have a concrete floor in situ and very little headroom.

 

[Andrew Bodenham]

I got it from Screwfix, product code 52649.

Completely inappropriate for a period property, of course, being plastic rather than lead, hemp, straw, mud, lime or dung. But it worked for me.