Concrete base for summerhouse.

Substrate laid and compacted.

So….do I put layer of plastic sheet above it then pour cement?

If yes, 1000 or 1200 grade?

blind it first with 1-2″ of builder’s sand. Then DPM.

Then shutter and fill.

Wrightyson is the man that knows his concrete, might be along in a bit, he cant help himself over a bit of agg & cement 🙂

50mm river sand blinding 1200 gauge visqueen, shutter then concrete.

Ok, so on top of the substrate I layer additional sand then Dom then concrete?

Good job I have 2 tonnes of builders sand lying next to the base area 😳

The sand is a little overkill, it’s basically there to protect the membrane, to be fair we don’t even get pulled on it by the building inspector anymore. However if you’ve got it chuck an inch down and use 1200 gauge poly as you suggested. What mix btw 😉

I would put a membrane underneath more to control the drying of the concrete and prevent de-watering (from the concrete) into the sub base.

As such I wouldn’t be concerned if its 1000 or 1200 gauge membrane.

The top of the slab is exposed to the elements so drying (eventually) will occur. The slab needs to be carefully “detailed” to prevent water collecting onto the slab and for this very reason I don’t particularly like them for sheds bases. A summerhouse may be different however I suspect not.

I’ve just done my potting shed using 6×4 pcc lintels , laid and levelled onto a type 1 base. Then I fixed 2×2 treated bearers to the concrete before fixing the shed floor. Gravel in between to allow free draining.