Solid Wood Flooring - Wood Subfloor, 2 Foot Cavity....eeeekk

[howser]

I have just purchased my Solid Wood Flooring (SWF) and now trawling through this forum reading the hundreds of posts trying to figure out the best way to install the flooring for my situation.


My existing floor is a standard planked wooden subfloor with a 2 foot deep cavity which has a earth/rubble bottom, it is very well ventilated.

I am planning to lay the SWF on top of the existing wooden subfloor but at 90 degrees. The skirting boards will be removed before the SWF install and the expansion gap around the perimeter will be hidden by replacing of the skirting boards.

1. Do I need to lay a DPM first on top of the existing wooden planked subfloor?
2. Do I then lay the foam on top of the DPM if installed?
3. Should I secret nail the wood or glue the tongue and groove and use adhesive foam layer?

I don't really want to lay another layer, ply layer, on top of the existing wooden subfloor first. If I did this wouldn't I find that after I placed all the layers down that the skirting board is half way up the wall and a step exists leading from one room into the SWF room!?


There are so many posts here that contradict one another, hence the reason for my confusion and my post on the forum.

The builder is planning to install the SWF in the next couple of weeks using nails.

Please help/advise.

Thanks in advance
H.

 

[WoodYouLike]

1. Do I need to lay a DPM first on top of the existing wooden planked subfloor?
2. Do I then lay the foam on top of the DPM if installed?
3. Should I secret nail the wood or glue the tongue and groove and use adhesive foam layer?

NEVER lay DPM ontop of existing floorboards - this will prevent the normal ventilation and can cause rotting!

Depending on the actual installation method you either use foam underlayment (installing the new floor floating) or not (secret nail).

If your new boards are installed perpendicular to the existing floorboards (90 degrees) you don't need extra hardboard or plywood first as long as your existing boards are pretty level.

Mind you expansion gap: rule of thumb is 3 - 4 mm per meter width of the room with a minimum of 10mm. So a room of 4 meter wide needs an expansion gap of around 16mm. And a room of 2 meter needs a 10mm gap (not that we've ever seen a room 2 meters wide, but you'll get the picture)

 

[Symptoms]

howser - secure the existing wooden subfloor, remove any high spots and pack out (below existing flooring) any serious dips to get the whole thing flat(level), vacumn clean. Secret nail new stuff straight onto original at your 90°. However, make sure your builder (has he any experience of floor laying are you confident to use him???) uses proper floor cleats (via an air floor nailer or similar) and not brads or 'lost-head' wire nails.

Tip: before you fix the subfloor try to determin cable/pipe runs below and mark these with thick black felt pen so as to avoid the later floor cleats from pierceing them. You don't have to lift loads of boards to do this just maybe one across the whole width of the room, then with a mirror & torch look below along the joists ... you will be able to see under the whole floor.

Tip 2: if you have any pipework in the void below now is the time to apply decent insulation to the pipes ('cos the void is "very well ventilated" - that means cold air via airbricks and check the condition of any unions 'cos once your new floor goes down you'll be stuf*ed to do any repairs below. We always try to introduce short lengths of flooring whenever a radiator pipe emerges from the floor so that if, in the future, access is needed these can be lifted without damaging a large area of floor (we remove the tongues off these 'trap doors' so they can be popped out; they are fixed with finish or brad nailer).

 

[howser]

ATTN: WoodYouLike or others who can help

Thanks for replying to my post.

WoodYouLike I had a clarification point on your second sentence in the reply. Basically, can I use secret nails on the foam underlayment? When I read your response I think that I can only use secret nails when NOT using the underlayment. And secondly would I be better using foam underlayment or not for laying my floor? many thanks.

 

[WoodYouLike]

secret nailing = NO underlayment
floating installation = underlayment.

hope this helps