Raised floor level advice

[Padraig Clarke]

I have a brick built extension, with a tiled floor which is very cold, so I want to raise the floor up about a foot and add somebody insulating boards. So I would just like some advice on the process. Thank you.

I need: DPM laid first on top of tiles, floor joists on top of DPM, insulating boards that sit in between the joist gaps, floor boards nailed into the joists.

1. Is the list above right?
2. Do I need an air gap between DPM and insulating boards?
3. I am laying down reclaimed timber floor boards. So with a gap between the boards, will it look weird if I can see the insulation between the gaps?
4 Am I meant to put something between the insulation and the top floor boards?

 

[tomfe]

1. Not really no.
What kind of floor have you got at the moment?

 

[Padraig Clarke]

I would say a concrete floor with large tiles.

What would you recommend?

 

[tomfe]

Sorry I reread your post again.
You can do it as you said as you have 300mm which if you use 150mm joists give you 150mm void to ventilate however this is not the best way as you'll have to add air bricks etc.

Do as you said but use battens ontop of the insulation to fix the floor boards. Use EPS to get your depth up to where you want it.

 

[Padraig Clarke]

Thanks! So if I understand correctly, I put down DPM down first, insulation boards on top of the DPM, joists on top of the insulation, then floor boards?

 

[tomfe]

Yes, the insulation will take the weight of the floor so you only need something to fix the floor boards to.
Depending on how level your original floor is you might need to pack these out. Or use sand under the insulation.

 

[Padraig Clarke]

Thank you. Is 50mm insulation boards okay or would you recommend 100mm?

 

[Padraig Clarke]

After reading and looking at some other posts and blogs, I think I have a good understanding.

I’ve seen other suggestions of DPM, then batons, filled with insulating boards, then on top plyboard. Finishing with floorboards.

Do I need the airgap at all?