It is currently 28 Mar 2024, 09:05
Mike G wrote:Windows and hatches are at very different levels
Mike G wrote:There are lots of half bricks in the bond I am using
Mike G wrote:More photos tomorrow, but the brickwork is nearly complete. Tomorrow I'll be putting the straps in, and doing the 50mm blockwork.
Wizard9999 wrote:Looking really nice Mike!
I think three courses will look really good, only two courses would run the risk of looking a bit mean, IMHO.
Wizard9999.
Mike G wrote:It isn't a dumb question at all, Bob. In fact, it is a very important one.
The concrete stays dry because of the DPM underneath, and because the upper edge of the slab is above ground level, enabling it to dry with air movement. I will be cutting the polythene back to where it turns up the edge of the slab. If I were to leave the polythene up the edge of the slab and tuck it under the brickwork, UV would destroy it in no time flat. Obviously things would be very different if the slab were below ground level, but some of mine (at the back) is about 9 inches above ground level.
We're talking about 160 to 350mm of C35 concrete here, and whilst I wouldn't advocate it, it would probably stay dry if there were no DPM at all. There is no way of having the DPM stop at ground level, even if you wanted it to. The DPC will be on top of the plinth, under the timber, and this is mainly because bricks absorb moisture then release it slowly, thus can remain damp for some while.
The proof of this particular pudding is in the eating, and the way to test for moisture in a slab is to put a piece of plastic on top of it for a day of two, and see if a dark patch emerges. Well, I did this with my previous workshop built to this same design, and it was dry as a bone.
Rod wrote:What sort of bricks are they - they look quite "soft"?
Rod
9fingers wrote:Ok Thanks Mike I understand now but a couple of things come to mind. It will be important to keep grass/weed growth away from the plinth
9fingers wrote: and any cupboards or other restrictions to letting the slab breathe, need to be kept away from the walls.
Mike G wrote:No, it is only the outside edges of the slab that need air to them. Bear in mind that moisture can only get in from the outside edge, and it just doesn't penetrate 6 inches in to the concrete, (and up) to clear the underside of the walls. The slab inside is not part of the ventilated-slab scheme, and you could perfectly well put a floating floor on this slab without running into trouble with trapped moisture.
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