concrete slab advice

11 Feb 2013
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United Kingdom
Hi everyone, first timer here. I have built slab for a large shed. The shed will be wood frame and divided into two rooms, one a store for a ride on mower, and the second room to be plaster boarded and made into a clean area store room. The slab consists of 7 inch of MOT with 4inch concrete slab. I have NOT put polyeuro sheet under the concrete layer, whoops. Does this matter? i know its best practice, but too late now! Thanks for helping.[/b] B
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Not much to be done now, as you say. There are liquid damp membranes available - google them up, and apply as per mfr's instructions. But it will depend on wear and tear usage, and how sound the slab is, to determine how effective they might be.
100mm slab is possibly a bit lean for perimeter weight bearing, so shear could be a problem unless the oversite is super sound. What will be the make-up of the roof?

Don't know what 'polyeuro' is but a lack of membrane would only be problematic if you are storing things that are sensitive to damp, in which case you would not be storing them in an unheated garden shed.
Thanks so much for the quick reply guys. When i say polyero i mean DPM. The liquid DPM looks good from Wicks, thanks. How about A DPM sheet ontop of the slab, with the wood frame built ontop of it, and chipboard flloor covering the DPM inside..?
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Thanks so much. Last question, i was thinking of building the wood frame on top of a single layer of concrete blocks, rather than directly on the concrete slab, just to give the base a bit more structure do you think thats wise? and how would i attach the wood frame to the blocks, drill the blocks and use anchor bolts? thanks again for your help.
Based on the assumption that your finished slab level is less than 100mm above ground level, then building up a block high might be the way to go.

Set the blocks at the slab edge, dont allow any lippage.

Fill the hollow cores with a semi-dry mix of concrete - mix it yourself.

-and set off-cut straps of galvanised tape into the wet mix ( see Simpsons Strong-Tie: mudsill anchors ). There are other methods !

Allow to dry.

Set your sole plate, or stud wall, on the block, square-off, check level, and tie-in to the strapping anchors.

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