Glue Down LVT subfloor question

[Gbuilds]

Im currently on a job where all the old floor boards are being removed and floor joist replaced (where necessary) to get a level & flat subfloor. Can I use a structural grade ply ontop of the new joists only, or would a I still need a layer of sp101 with feathered skim finish. I realise this has been discussed before but I get a different responses from floor layers/ Lvt suppliers and general builders. Is the issue more to do with the glue used to construct the 18mm ply? Any help would be appreciated. Worth mentioned that im trying to keep the floor build up to a minimum. Thanks

 

[dazlight]

18mm ply
6mm Sp101
Feather finish / fibre compound
Or
22mm chipboard ( high grade )
6mm Sp101
Feather

 

[Gbuilds]

Appreciate that @dazlight

 

[dazlight]

I take it you want glue down (dry back) LVT ?

 

[Gbuilds]

Yeah mate. Never been too impressed with the click.

 

[Gbuilds]

Is self leveller over the ply not as efficient as the sp101 option?

 

[crazydaze]

Is self leveller over the ply not as efficient as the sp101 option?

If the floor is 'good' then if fitting straight plank LVT you should be ok with feather and fit direct to the sp101 ply, you shouldnt fit direct to the wood substrate.

If you are doing any kind of design work like Herringbone, Borders or Basketweave etc it's almost essential to Self Level over the Ply with a fibre reinforced screed such as Mapei Renovation.

 

[Gbuilds]

Thanks @crazydaze, yes it will be herringbone layout. My only concern is whether its similar to tiling in that if the surface laying the lvt onto isnt flat will gaps start appearing between the planks. Or is lvt more forgiving because its flexible.

 

[crazydaze]

Thanks @crazydaze, yes it will be herringbone layout. My only concern is whether its similar to tiling in that if the surface laying the lvt onto isnt flat will gaps start appearing between the planks. Or is lvt more forgiving because its flexible.

It's the same as tiling, it's not flexible in such a way that you can bend it. You can manipulate it to a degree but you cant bend/curve it which is why you need to Screed over the ply to get the floor as flat as possible.

It's always prudent to use a adhesive suitable for use over Under Floor Heating as well as even if you don't have UFH, if there is direct sunlight or hot-spots etc, the install will be more stable.

 

[Gbuilds]

Thanks @crazydaze