Installing Solid Wood on Ply

[Damian30]

Hi,

After spending several confusing months deciding how to install my 20mm (105mm wide) solid oak floor, after reading some of the useful advice on this forum, I have now decided to secret nail it on 3/4 ply.

Now being under pressure to install the floor, I would appreciate any answers to the following (possibly dumb) questions:

1. The existing floor is 5 year old concrete, although broadly flat, there are a few depressions up to 6mm below the general floor level. Would be worth using a self-levelling compound to get the floor really flat before fitting the ply?

2. Do I need to put an additional DPM (either liquid or sheet) down before fitting the ply (I have checked the moisture content of the floor and it appears to be okay)?

3. Is there any particular sort of ply I need to use and can you buy it from most timber yards?

4. What is the best way to fit the ply - screw down in the corners and centres - what size/type of screw is best to ensure that it stays down?

5. From previous posts, I don't think you need to leave any expansion gap with the ply.

6. Does it really matter which direction you lay the ply (or the size of the ply sheet)? Or do you lay the grain of the top sheet of ply at 90 deg to the direction of the wood planks?

7. What size nails will I need to fix the wood planks to the ply and can a portanailer be hired from most hire shops?

8. Would 10mm expansion be sufficient - I have 20mm skirting boards so can increase if necessary? I also have a curved stairwell to fit around which I will pad out with underlay/carpet - could I reduce below 10mm in this area or best not to?

9. As I will be raising the existing floor level by about 40mm, I am going to have to cut the doors down. What is the best way to do this and are there any issues to think about (e.g. is the supporting timber within the bottom of the door think enough to be reduced by 40mm?)

Thanks for all the information on this forum and any help with the above questions would be much appreciated. It would also help me avoid being strung up by the missus for taking so long to install the floor!

Many thanks,

Damian

 

[WoodYouLike]

Hi,
After spending several confusing months deciding how to install my 20mm (105mm wide) solid oak floor, after reading some of the useful advice on this forum, I have now decided to secret nail it on 3/4 ply.

Sorry Damian, but that is impossible. For secretely nailing you have to use 50 - 60mm long nails. This can't be done on 3/4 ply I'm afraid.

 

[Damian30]

Hi,

Thanks for the quick response - a number of wood floor suppliers/installers have said that you can use 1.5" nails at 45 degrees or 2" nails at 33 degrees angle.

Now I am really confused....

Thanks,

Damian

 

[WoodYouLike]

What's that in mm? (Not English, sorry )

 

[Damian30]

Sorry WoodYouLike...I normally use metric but was just quoting off a website.

1.5" = 38.1mm
2" = 50.8

I guess the angle of the nail dictates how it should be installed into 19mm (3/4" ply).

Thanks again,

Damian

 

[WoodYouLike]

8. Would 10mm expansion be sufficient - I have 20mm skirting boards so can increase if necessary? I also have a curved stairwell to fit around which I will pad out with underlay/carpet - could I reduce below 10mm in this area or best not to?

Rule of thumb by solids: for every meter wide you need 3mm expansion gap with a minimum of 10mm.
Thickness of skirting boards is fine (20 - 22mm by solids)
Don't reduce expansion gap around stairwell, if needed, fill gap with cork strip (only there, not anywhere else).

 

[JohnD]

As it's a concrete sub-floor, I don't see the point in laying ply. Why not just fix battens, and fasten the boards as if on joists?

 

[WoodYouLike]

Why not install floating, after you levelled out the concrete floor?
(Sorry to confuse you, but installing battens seems to be so typical English, since you all seem to be so used to joists? with a -level- concrete floor there is hardly any need to install fixed to battnes or ply. thought Damian knew that, reason why I didn't mention it to his question).