Can I screed on a suspended timber floor?

eamon11

hello folks,

I am refurbishing an old bungalow and all rooms bar 1 are screeded. I will be raising the floor level and laying a screed on top but this room is a very solid timber floor.
Is it ok to screed on this?

T hanks in advance

gutteruu

Nope. Rip it up and pour the whole thing. Any movement will crack the floor.

eamon11

thanks Gutter, much appreciated. Can I ask how screed works on upper floors with timber joists and plywood? Would nt there be movement there also?

gutteruu

Sorry, my last comment made it sound like fact but it was more my opinion. I wouldn't do it personally, although AFAIK screed companies say you can. In fact heres a quote from 'easy screed'

Easy Screed can be poured on both the ground and first floor of timber-framed houses. As it is installed at a lesser thickness than standard screeds, it is weight-saving and therefore generally suited to first floor applications with underfloor heating. Easy Screed weight 20kg per m² for every 10mm of material installed, for example 35mm Easy Screed, weight 70kg/m². Please ensure you check the weights with you engineer.
In all installations over timber joists with ply covering, we recommend the installation of an acoustic/soundproofing mat beneath the underfloor heating to help reduce sound transmissions between the floors of the house.

duckcfc

I wouldn't do it. Pull the floor, fill in then screed.

eamon11

ye are probably right lads.

I have a foot of space to fill below the floorboards before I even begin to insulate and screed. I have sand already. What would be a good stone/chipping size to get in order to mix some concrete for down there?

Thanks again

gutteruu

I would fill it with compacted 804 to bring up level. (edit)2 4 to 8 inches of Insulation then pour 3-4 inches of concrete. You plan to mix the floor yourself?

BryanF

gutteruu wrote: »

I would fill it with compacted 804 to bring up level. 2 inches of Insulation then pour 3-4 inches of concrete. You plan to mix the floor yourself?

I'd go with 200mm of EPS insulation

Markcheese

BryanF wrote: »

I'd go with 200mm of EPS insulation

Its a lot lighter to move than gravel - if you've got space to fill make a virtue of it -

eamon11

thanks lads,

yes I will be doing it myself. Thing is though, wouldnt eps be less solid than the wooden floor presently there?
And, gutteru, what would be the best way of compacting the gravel in the small space I will be working in solo?

Cheers

gutteruu

Insulation will shrink slightly initially with weight and stay exactly as is. Its designed exactly for this. It isn't affected by things like heat or moisture. Wood would crumble from moisture and no ventilation. Crack from weight etc.

The other lads are right about 8 inches of insulation. Its much easier than bringing in 804 and will pay for itself with heat saving. To compact 804 you will need a wacker plate from plant hire company. 804 would be around 40 quid for an 8x4ft trailer, wacker plate is 40/day. Be careful if using a wacker plate near pipes. If your not going insulation route compact the 804 in layers. Don't put a foot in and just compact the top.

agusta

fit a plastic membrane underneath the insulation,100 mm insulation is loads.Why would you putt 200 mm insulation in one room why you have very little in the rest of house,its like getting a treble glazed window for that room and leaving the rest of the house single glazed.it doesnt achieve anything.6" concrete

eamon11

thanks a lot lads,

the rest of the house will have 100 mm and 75 mm insulation, and 3 inch screed.
The floor is very uneven and sloped hence the necessity for different thicknesses of insulation.

Where this wooden floor is will be the bathroom.

Cheers

Safehands

gutteruu wrote: »

Nope. Rip it up and pour the whole thing. Any movement will crack the floor.

Not necessarily true. It depend on the thickness of screed he wants to do. There are a number of self levellers can be laid as floating screeds on timber, especially if the timber is solid. So, don't dismiss it.