Re: Re: Suspended Ground Floors or Something Else

Hi teak,

The “give” in traditional suspended timber ground floors is vastly overrated.
In fact if you find there is much “give” in any suspended ground floor, have it inspected unless its over a full basement.

Normally the timbers bear on joists bearing directly timber grounds on a DPM on tassle [AKA honeycomb sleeper] walls circa 1200mm c/c.
Tassle walls are walls with a bond which leaves opes of say 1/2 a brick to promote circulation of air in the interstitial space under the floor.
These bear directly on the slab which should have some sort of outlet/grille from the underfloor area in the wall level with the slab to drain it.
Under-specified [and older] timber 1st floorsand above can exhibit significant “bounce” but that’s due to minimal specification, a fault, or rot.

Below are outlined two specifications you might check against your local building code ( is that in America or Canada somewhere? ).
Both seem to be compliant and I have specified something similar to the one with UFH.
These are both off-the-cuff this morning so you should check the details.

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Without UFH:

Fully “Floating” half-timber finish 15-19mm (enough to take three sandings)
On separating layer
On absorbent matting
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With UFH:

Proprietary floating floor
On clip system
On lightweight screed incorporating
Proprietary UFH system with specialist threshold connectors
On foil backed insulation turned up at room perimeter.
(there may also be a separating laying in this spec -some suppliers may require it, some may not)
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Slab and Substructures:

On min 150mm slab sealed with dust-proofing agent
On min 75mm HD insulation
On Radon Gas Barrier with Radon Gas Collector Box in Hardcore with evacuation pipe.
On min 50mm blinding (compacted sand or lean mix)
On 150mm “whacked” layers of graded hardcore free from soil, impurities and organic material.
On prepared and suitable bearing ground with all soft areas tamped and filled
All topsoil and vegetation removed including rootlets
All projecting rocks removed from exposed bearing stratum

(Note: in Ireland the Radon Gas Barrier doubles as the DPM although some local authorities prefer 2 no. layers of 500 gauge Visqueen or similar)
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This isn’t a proper specification, just one to set you on your way.
There is a whole host of stuff regarding the site investigation I haven’t referred to.
I’m assuming from your posts here you have a clue, but I’m including the disclaimers for those reading who many not be so well informed as you.

ONQ.