Hi All,

 

Carrying out a DIY small infill extension and can almost see the light at the end of the tunnel! 

 

I am looking for suggestions on how to bring the extensions floor level up to the existing property. The extension is the area where you can see the green vapour barrier in the photo. Underneath is Celotex insulation and the joists of the existing house finish on a course of bricks under the plyboard surrounding the green vapour barrier.

 

I had initially planned to lay 50mm of screed to meet the floor boards of the existing house, however is there an easier/cheaper alternative to screed that would be acceptable with building control, such as laying a wood frame with ply board on top which I believe is referred to as a floating floor? 

 

Many Thanks 

Joe 

 

Take up the rest of those boards use 22mm chipboard flooring glued and screwed down, float this over the extension bit, making sure it’s nice and level. 
you will always feel that the corner bit is a bit bouncy. 
you could add a ply layer to your insulation first and screw it down through the insulation, then bring the chipboard over the top, this will take out a bit of bounce. 
every solution will have a bit of compromise. 
 

or take up what you have, extend the joists across the new bit, then board over the top. 
you ideally want one finished thing not bits and bobs. 
 

what is that green strip for, wasn’t that where the old wall was. 

Edited April 15, 20242 yr by Russell griffiths

Thanks @Russell griffiths I think I'll add a layer of ply, then chipboard over the top, as it's a 50mm depth so this will help bring it level with the rest and add extra support to counter act the bounce. Is this method generally acceptable with building control?

 

The green strip is marine plywood. Initially I was going to bring the screed up to the level of the plywood but I didn't like the idea of having different types of finished floor hence this post.

 

Thanks for your help 

30mm of PIR insulation and then 18mm of P5 boards over the insulation screwed down to the floorboard level, with 3.6mm plywood over the P5 as a binder?

How much insulation is under the existing floorboards? Have you sealed up with foam yet to nuke all the drafts?