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https://www.askthetrades.co.uk/cgi-bin/yabb/YaBB.pl DIY Forum >> Building Questions >> Pouring Concrete under a floorspace? https://www.askthetrades.co.uk/cgi-bin/yabb/YaBB.pl?num=1247931253 Message started by Tony Thompson on Jul 18^th, 2009, 4:34pm

Title: Pouring Concrete under a floorspace?
Post by Tony Thompson on Jul 18^th, 2009, 4:34pm

Hello All

I'm thinking of having a real wood floor in my hallway and to stop it sounding hollow, like laminate on florboards often does, I am considering ripping out he floorboards and joists and filling the entire hallway space with concrete.

It will mean re-routing a few pipes and cables but I'm happy to do that. So if you can then imagine what is essentially a long thin space running from the front of the house to the back with 3 of the walls external and one an internal honeycomb wall supporting the walls of the lounge and dining room, I want to fill that with concrete and have the wood floor laid directly on top.

The questions I have are:
1.Would it be safe to pour that much concrete in the space? I'm not too worried about the strong external walls it's just the single honeycomb wall that concerns me.
2. Can anybody spot and problems with this idea?
3. What type of membrane should I consider and how should I prepare the area (apart form filling in the holes in the honeycomb wall of course) ::)

The space currently under the floor is neglible at one end by the front door (250mm / 10" maybe) sloping away to maybe (600mm / 2') by the back door.

Would appreciate any advice, tips or steer that this community can offer.

many thanks

Title: Re: Pouring Concrete under a floorspace?
Post by Joiner on Jul 18^th, 2009, 5:55pm

Seems a bit extreme, Tony. If properly laid the wood floor shouldn't be noisy and will last for generations on the suspended joists.

If you're really that concerned with the noise of footfalls, you could always fit herringbone noggins between the joists to give the floorboards that little extra support.

The honeycomb wall gives a good circulation of air around the underfloor area which is what will make the existing floor last a very long time.

I'd think again.

Title: Re: Pouring Concrete under a floorspace?
Post by woodsmith on Jul 18^th, 2009, 6:22pm

It sounds a lot of work with potential for problems down the line. Plus a hardwood floor laid on concrete will not necessarily sound solid as it will depend how you are planning to fix the new floor down.

I agree with joiner, but as well as bracing the joists, I would screw 22mm flooring grade t&g chipboard over the joists, run a thick bead of flooring adhesive under each new board and then use tongue-tite screws, or a Portanailer to invisibly fix the floor through the tongue.

Title: Re: Pouring Concrete under a floorspace?
Post by Tony Thompson on Jul 18^th, 2009, 6:45pm

Thanks for your advice - the bracing idea would probably do it. I think I may do that instead.

I just recall I house I lived in once that had a parkay floor that felt so solid - I assumed it must have been laid on a concrete base because even when wearing shoes there was no discernable noise. Compare that with my current neighbours house (I can hear them from next door when they pace up and down) who have laminate on floorboards and I'd convinced myself that a concrete infill was the only way to go.

Thanks for responding so quickly by the way :)

Tony

Title: Re: Pouring Concrete under a floorspace?
Post by Joiner on Jul 18^th, 2009, 8:06pm

It sounds as if your neighbour's laminate hasn't been laid properly. If laid onto the 'underlay' specifically designed for laminate flooring (it's about 3mm thick and comes in a huge roll) there is very little noise, unless you're in a flat UNDER them and they're wearing Dr Scholl's! You're lucky you're alongside them.

Title: Re: Pouring Concrete under a floorspace?
Post by CWatters on Jul 19^th, 2009, 9:46pm

Are the existing floor boards "real wood"? Perhaps you just need them resanded?

If you secret nail/screw and glue solid wood or 14-21mm Engineered wood properly it should be fine. It's mostly only thin laminate laid over concrete that sounds like thin laminate laid over concrete :)