The Brew Cabin

Posted: **Tue Oct 25, 2011 12:54 pm**

Hi

I'm planning a 6m x 3m wooden shed on a slab base. Very useful site for guidance on how to build the slab, but I have a question regarding the DPM. At the bottom of this page http://www.pavingexpert.com/concrete.htm there is an excellent cross-section of a freestanding slab for a sectional shed/garage - similar to what I'm doing. It suggests having the shed wall around 6" in from the edge of the slab. My question - if you just trim the DPM around the top of the slab, how do you stop water puring down the side of the shed, onto the 6" of exposed slab and then running down on the inside / top of the DPM - which defeats its purpose?

My thought would be to leave enough DPM to wrap round over the top of the edge of the slab and underneath the bottom of the wall (which will be a 4" x 2" foot plate in my case). But is this right, or is there a better way to do this?

Thanks in advance

Posted: **Tue Oct 25, 2011 4:36 pm**

the DPM is there more to help the concrete cure correctly
if its a sectional garage most people would only go 75-100mm beyond the size of the garage ,then run a strong concrete fillet around once the garage has been erected
also most garages should have at least a 1:60 fall towards the door so that any fuel spillages do not stay inside
when i have done these bases they have been around 125mm thick with sheet mesh all around the perimeter,and maybe 225 at the edges

cheers LLL

Posted: **Wed Oct 26, 2011 9:23 am**

Thanks LLL. In fact mine will be a general storage garden shed with a stud wall with featherboard on it. So the weight will not be as great as if it were a sectional concrete garage. I was hoping to get away with a 4" slab as there wil be very little load on the floor, but I like the idea of running some mesh around the outside. May also look at making it a bit thinker at the edges...

Any other comments or suggestions welcome!

The Brew Cabin

Dpm on slab question