Fixing a floating floor from a previous garage conversion

[skylineboy]

Evening all, hoping for some advice on the best way to tackle a springy & extremely squeaky floating floor in a garage conversion. The garage was converted before we purchased the property and the flooring raised to meet the concrete slab in the rest of the ground floor. As an FYI the rest of the ground floor now has overfloor UFH installed using Wunda Therm premium boards, the plan will be to do the same in the garage conversion once the issues are fixed.

Tonight i've taken up a small section of floor to understand the construction. We have from ground up.

DPM (bottom)
75mm joists laid onto DPM (no air bricks installed)
22mm T&G
100mm Polystyrene Blocks - (not sure if this is PUR it's extremely soft)
22mm T&G (Top layer).

So in total I have 220mm to raise from ground to slab height of the rest of the house.

I want to ensure this is done correctly, once the UFH boards are down there's no going back to fix or adjust this. Can anyone advise on the best course of action please, can I take up all the T&G, maybe reuse the polystyrene blocks and then a slab on-top to bring it up-to level? Basically looking for the cheapest way to do this right.

Thanks in advance.

Tom

 

[motorbiking]

What is the spacing of the joists? What you describe should be fine assuming the joists are supporting properly. It looks like standard Polystyrene boards.

How do you get 75mm joists and 100mm poly? Is there a gap of 25mm between the joist and the T&G?

 

[skylineboy]

Thanks for the reply, this is the current setup with 600mm centres on the joist. The joists aren't hanging they're just laid ontop of the DPC with the T&G above nailed on. No ventilation between the joists if that matters.

At the moment it is horrendously noisy, the invoice for the original work suggests the T&G was glued, but either it wasn't or was done very badly. I'm unsure if I rip out the top layer of T&G and Insulation and replace it with PIR and fresh T&G and expanding foam glue the joints, or just bite the bullet and pour a slab.... maybe I can use the original insulation and pour a slab on top?

I just need to kill the squeaking/creaking completely before the UFH and laminate goes down.

Cheers

 

[motorbiking]

Is the bottom area vented in any way? Its quite a common problem for this design.

Another layer of T&G or OSB may Help
perpendicular beams in the poly layer could help, but it will compromise the insulation.
You could take the whole thing back to the DPM. Lay the poly, perhaps add another 25mm of poly/celotex and get a new concrete slab poured on top. Ditching the beams and the T&G

 

[skylineboy]

No exterior wall vents, there could be vents into the cavity maybe, but hard to see without ripping it all up, I expect it's not vented.

Thanks for the help, additional layers aren't really possible, the ceiling height is already low. Guess I best start pricing up a layer of Celotex and a concrete pour, an additional 25mm of Celotex would mean I need roughly a 95mm slab. Room is 5.4x5m so about 2.56m3.

Would I need to steel mesh/reinforce the slab?

 

[motorbiking]

Worth seeing if anyone else suggests anything.