Oak Floor over batons or plywood?

[ChrisRFT]

Can anyone give advise on installing solid oak 20mm T&G (all-round)
flooring. I have a concrete floor (3 years old with DPM below it) which is 5" below the level of the oak floor. I had thought of installing batons or small joists directly to the concrete or batons to the concrete plus 20mm plywood onto the batons, then blind nailing the floor to the batons or the plywood with an expansion gap at the skirting boards. Should I fit a DPM between the plywood and the oak? I'm not keen on glueing the floor down because I don't think it will be able to move so easily as it expands and contracts. The concrete should be dry after 3 years, but there is a small amount of damp in the lower wall bricks at concrete level (wall has been damp-proofed, injected ) so there could be some moisture to think of. Realise this is a bit unusual and I might have asked some daft questions - first floor!

 

[WoodYouLike]

flooring. I have a concrete floor (3 years old with DPM below it) which is 5" below the level of the oak floor.

Not really sure what you mean with this?

 

[ChrisRFT]

The existing concrete is 5" below the level I need to build the floor at , it has a visqueen sheeting between it and the sand/ hardcore bottom layer. I put the concrete at a lower level believing that it would be easier to cramp up a wooden floor onto joists or batons fixed directly to the batons. Hope this makes it clearer?

 

[ChrisRFT]

Sorry - Ooops, too many batons - last "batons" should have read "concrete"

 

[WoodYouLike]

Ah, I see. Now I can't suggest to install the floor floating on a combi underlayment (including DPM and sound-insulation) or you have to install plywood thirst (on DPM sheets) and use foam underlayment between plywood and wooden floor.

 

[ChrisRFT]

Thanks,

Do you mean I should fix batons onto the concrete, then fit a DPM, then plywood then foam underlay and blind nail the boards down. What type of DPM should I use with this? I have heard of builders paper and even a liquid damp proofer painted onto the sub floor. There seem to be lots of options - I'm not sure what will work? Also will the floor feel like a trampolene if it is on foam, or if it is fitted as a floating floor?

 

[WoodYouLike]

No, sorry. I mean install plywood to the concrete on a DPM layer to cover the height diffenence This type of DPM comes in large sheets (Wickes do them). Battens are a waste of materials and money. On top of the plywood lay foam underlayment and then install the wooden floor floating on top of that (glueing the T&G's) The foam is only 2 - 3 mm thick and won't 'bounce'

Hope this helps.

 

[ChrisRFT]

Its becoming clearer - I think! See what you mean about the batons and joists, but I will have to raise the floor from the concrete by 5 inches (125mm) (the living room where the floor is going in is 5 inches below the kitchen floor level) so I'll need to add some height to the concrete before I fit the plywood, then the underlay then the oak. Would the DPM be a thick plastic type and is there a trade name for the DPM and the underlay - will try the Wicks site. Is a floating floor fixed down anywhere? If not, how do you push one board against another to get a tight fit without the whole floor moving and does the whole floor expand like a big sheet if it is floating. Lots of questions - just want to check as it'll be expensive if I get it right and very expensive if I get it wrong!

 

[ChrisRFT]

Its becoming clearer - I think! See what you mean about the batons and joists, but I will have to raise the floor from the concrete by 5 inches (125mm) (the living room where the floor is going in is 5 inches below the kitchen floor level) so I'll need to add some height to the concrete before I fit the plywood, then the underlay then the oak. Would the DPM be a thick plastic type and is there a trade name for the DPM and the underlay - will try the Wicks site. Is a floating floor fixed down anywhere? If not, how do you push one board against another to get a tight fit without the whole floor moving and does the whole floor expand like a big sheet if it is floating. Lots of questions - just want to check as it'll be expensive if I get it right and very expensive if I get it wrong!

 

[WoodYouLike]

Well, you can tackle this height problem between living and kithcen in various ways. One is as you suggested, another (cheaper) option is to leave the level as it is now, no plywood but use a combi underlayment (where the DPM is already attached to the sound-insulation foam, 3mm total thickness) and install a wooden like a ramp or reducer.
Floating is floating
When you start installing the floor you normally start at a straight wall, use spacers (10 - 15mm thick) to keep your expansion gap and install row after row, next to row, next to row. If your floor expands (Autumn etc) the whole floor will expand a little bit, hence the expansion gap. In winter (heating season) the whole floor will shrink a little bit: that's wood for you.
After yoi have installed the whole floor, remove the spacers and place your beading (we prefer the flat ones, but scotias or quadrants will do the same job of covering this gap)

Questions no prob, questions don't cost money, just time

 

[ChrisRFT]

Very interesting, I'm getting my head around the idea of the floating floor now - I'm more used to softwood T&G fitted directly to joists and clamped up tightly by cramping from the joists, then nailing down. I don't know what you mean by wooden threshold - how would this give me the height I need and what would I fit the combi underlayment to - plywood, or joists/batons or threshold

 

[WoodYouLike]

Just suppose you leave your concrete floor as it is, with the height difference you have now (12.5 cm) = step.
Lay the combi underlayment (which comes on a roll of 1 meter wide with an overlapping self-adhesive strip to 'seal' on to the next row of underlayment) on the concrete floor (foam face down, normally)
Install your wooden floor floating as explained above. Leaves you a 'step' of 10cm. Indeed a standard threshold wouldn't do (goes up to 2.5 cm), but perhaps you can have made one bespoke?
Or do you want one and the same level to the kitchen? Then you have to install (floating is the most easiest) plywood or other thick and level product of 10cm (stay away from extra concrete, every inch will take 30 days to dry)
(Still don't understand why you created that much height difference in the first place?)

 

[ChrisRFT]

I (mistakenly) thought that I'd need to cramp up the oak onto joists, and I left enough space so that I could fit them directly to a concrete base - had removed earth plus quarry tiled floor and didn't want a suspended floor over bare soil, so fitted the concrete with a DPM under it - should have kept to your keep it simple (and cheap)! I did want to fit the floor at the same level as the kitchen which is tiled - not sure how to disguise the expansion gap between the tiles and the oak at the doorway - did think of an oak strip with a small tongue into the gap and a bevelled top? Thanks for your patience

 

[WoodYouLike]

not sure how to disguise the expansion gap between the tiles and the oak at the doorway - did think of an oak strip with a small tongue into the gap and a bevelled top? Thanks for your patience

That's simple There are so-called T-bars available you install in the expansion gap, overlapping both wooden floor and other area with the T, plus leaving you enough remaining expansion gap between T-bar and wooden floor.

 

[ChrisRFT]

The T bars sound great. Just to recap on the floor: build up the level, fit plywood, fit combined DPM and insulation, glue oak together (PVA) leaving expansion gap at walls etc and fit T bars at the thresholds. It looks like you do this all the time, so it must be able to cope with central heating and the English climate?? Thanks again