Hi Robin, I think you can get t&g chipboard laminated to PUR foam - this kind of floor just 'floats', Floorboards fixed on top?

One of the advantages of the screed however is that it adds to the airtightness of the build

What about the UFH ,
Perhap you could use the pre-routed EPS as suggested then if the final floor finish is T&G
you could float this on top , glueing and clamping the T&G in stages as you fit.
Might give you a slight bounce in the floor, not that solid feel of a screed/glued/wooden floor
whats your heat source ? is the screed being used for thermal mass ?

Posted By: RobinBI'm a bit sick of all the concrete and "things that will take ages to dry out" that are going into my house. I've got beam and block on the first floor and it's planned to have 30mm foam and 70mm screed on top. So sounds like the screed isn't intrinsic to the structure, or is it?

Ideally I'll replace the screed with foil face foam, ready routed for low temp UFH pipe - I'm putting wood on top. What are my chances of success with carefully dried T & G floorboards?

It should work fine but go for Engineered boards. We did something like that, our first floor and a large part of the ground floor was built as follows...

1) Lay Beam & block first floor ( I think a cement grout was brushed on but can't swear)
2) Fit 80mm (?) Osma UFH foiled insulation between 80mm battens screwed to the B&B
3) 21mm engineered Oak secret nailed and glued to the battens.

Works well. Not having screed makes for fast warm up time.

I think we actually used two layers of insulation in the end (eg celotex with Osma profile on top to get the right depth).

Engineered wood (eg 6mm oak on 15mm ply) is much more stable than solid wood and looks just as good. You can use wider boards with less risk of cupping. eg 180-210mm wide is ok. Must be 18mm thick or more.

In the bathroom we have stone over screed. If you have a similar mixture you may want to use deeper battens and insulation to match the levels.

I'm not convinced you can do without the battens. In the past I've heard of problems with the insulation breaking up in high traffic areas due to the slight but repeated flexing of the boards.

PS: I think the B&B company provided brackets to hang 38mm battens off the underside of the floor. 12mm plasterboard was then fixed to that. Choose the right batten thickness if you want recessed lights! Typically 38mm + 12mm plasterboard gives a 100mm deep void between the conc beams. Is that enough for your lights? Some need min of 110mm.

PPS: Check your BCO is happy that your proposal meets Part E. He should be but I had to jump through hoops to avoid a sound test.

Not really thought about it. If they shrink a bit in height I guess that would load up the insulation a bit more. That might possibly be an advantage - eg by keeping the foil spreader plates pressed against the underside of the wood floor? We didn't take any special precautions to ensure the wood was especially dry. We used regular timber with whatever moisture level it had at the time. Been down three years.

We've only had one minor problem... In the dining room the boards go the short way accross the room meaning we have a lot of boards joined side by side. One of the T&G joints opens and closes about 3mm with the seasons. I suspect that not enough glue was used on that joint compounded by the floor shrinking slightly in width.

The direction you lay the battens dictates the direction of the final boards - So plan ahead as that can effect the whole look of the room.

Use 5cm of sand between the studs and lay the wooden floor ontop

Yes -- = big time air leaky

<blockquote><cite>Posted By: fostertom</cite>For intermediate floor, surely airtightness doesn't come into it?</blockquote>

I thought that, but aasumed that because it was insulated there must be an unheated space below. Perhaps Robin can clarify?

Robin,

in answer to your question do beam and block floors need screed...

This depends on how your engineer has designed the building, in your case the 1st floor is acting as a structural tie to the retaining walls. The orginal engineers design was to use the screed as the structural tie, by building the block and beams into the external walls and casting these in solved this (otherwise we would have had to screed it prior to continuing up with the ICF walls)

What ever floor make up you want to use, I'd always run if past building control as they may question sound transmission or just not be happy with itm they can be sticklers, always back it up with a drawing to them.

As for airtightness, if your not using a screed then you will need to take additional measures for airtightness on the first floor, plus you will need to insulate under the garage ceiling or increase the insulation on top of the block and beam to meet minium insulation levels.

Remember your screed / final floor finishes must substancial enough to dissapate point loads from the blocks on the beam and block floor.

As for drying out times, just put a vapour barrier down on top of the screed and you can put your wood floor strait down on top.

Cookie

I would not put any wood that I had paid for on top of undried out concrete screed even with a vapour barrier -- far too risky -- wait til it has dried out then do it or you might have to do it twice.

Vapour barriers - needless to say thats what there designed and tested for.

Ali.gill
Your not familiar with Robins designs, ask them for a copy its spectacular

The house is ICF so has a make up of 67mm EPS 250mm Concrete 67mm Eps then a further 72mm Kingspan K18 insulation backed plasterboard.

The ends of the Beam and Blocks are set on top of the concrete walls, then the new ICF wall built on top then infilled with pumped concrete to a 175mm slump and 10mm aggrigate, there is no air gaps around the perimitter.

The purpose of insulation under the garage ceiling then removes the thermal bridging of the block and beam on the internal skin of the ICF blocks

However if she chooses not to screed it, or put a vapour barrier down, then the entire floor will leak air like a sive.

Best advice for wood floor if your worried is contact an installer and ask them to put down their own vapour barrier move the risk to them.

If your not planning on screeding it, and looking to set the underfloor heating pipes in the routered insulation then the vapour barrier (and your air seal) can go strait down on the beam and block then insulate on top.

You have 300 tonnes of concrete (recycled fly ash), beam and block flooring and dense concrete blocks that have been sat outside all winter... If you want to wait till the building dries out, then your going to be waiting a long long lonnnnnggg time!

If I put vapour barrier over my soggy beam and block floor won't it just grow mouldy under there? I just don't like the idea or sealing in all that wet. I recognise that I do need to make it airtight.

Ali.gill as a rainscreen there is variously render, stone slips and timber siding with a VCL. Apart from the wood they are attached directly to the EPS. Render from Sto, Pavatex or WBS, Stone slips from Bingley, timber - just treated rough sawn wood laid horizontally over verticla battens - bit of an experiment - but a fairly cheap one.

I would eventually dry out but it could take years

Beam sheild is only for ground floors health and safety reasons note if your a self builder and can source it without manufacture nowing its for first floor it will pass building regs but will need concrete on top so as to pass sound regs but you could use it on a flat roof as there are no sound regs for a roof
If this is a new build choose your blocks well or you may fail transmition of sound test on building regs

Posted By: jolly-green-giant</cite>Beam sheild is only for ground floors health and safety reasons

That is interesting - the problem I came up with was an issue with fire rating and fixing the ceiling. I don't know if they are really issues or just a lack of documentation and BBA approval - I would have thought a Fermacell ceiling on battons with block and beam batton clips would have worked well.

Health and safety issues being falling through while installing and before external screed, boarding etc is installed? I could install a scaffold platform under the area to avoid risk of falls or have harness used, it's only at 3 meters.....