Using Waterproof Membrane on Summerhouse Base

[Handsj]

Hi,
I’m building a 13ft x 12ft summerhouse and the base is on slabs and is around 12inches off the slabs, I am putting OSB as the floor on the base and wondered should I put waterproof membrane between the joist and the floor before I put the floor down?

any help greatly appreciated.

 

[Doghouse Riley]

Hi and welcome.

The most important thing is to get plenty of air circulation under the building.

My 9' X 9' summerhouse, (roof is 12' X 12' ) has 3" X 2" joists resting on bricks, on paving slabs. I put bits of vinyl pool liner between the joists and the bricks.

There are 9" "skirts" on 3 sides that finish a couple of inches above the paths.

Photographed in 1987 during the build.

A contemporary photograph.

There's no skirt at the back just a wooden frame with a wire mesh covering. So it gets plenty of air under it. The overhang of the roof which has guttering on this one side, prevents any water getting under the building, the paths fall away from it.

There are two bug-proof vents in the back wall.

The skylight, is just like a box lid, I raise the front and place a ventilator made from two halves of a dishwasher cutlery basket and a bit of 3" X 2" to get some air through it, as it gets very hot in there in summer. But I open one of the doors if I'm home during the day.

It;s made of softwood and still has no rot after thirty-three years.

I have replaced the roofing felt. I used a strong non-tear polymer type ten years ago. It's still in perfect condition.

It gets regular coats of Dulux mahogany wood-stain it's over £50 for 2.5 ltrs, but is well worth it.

 

[Handsj]

Thanks for your reply and pictures are great, given me another couple of ideas, I was thinking of putting the membrane across all the joists before applying OSB, my worry is in case any water gets in before building the structure around it, rain has delayed things already. My summerhouse is also around 8-12 inches off the ground for levelling.

 

[Doghouse Riley]

Thanks for your reply and pictures are great, given me another couple of ideas, I was thinking of putting the membrane across all the joists before applying OSB, my worry is in case any water gets in before building the structure around it, rain has delayed things already. My summerhouse is also around 8-12 inches off the ground for levelling.

This is the "how to" YouTube video...well (a series of photos) of the build. It's had over 80,000 hits, (so there maybe one near you).

I made it very sturdy.

This is our son on the roof when he helped me re-felt it... (he had the mucky job). It easily took the weight of both of us up on it, so that was my 12st and his 14st.