Summerhouse

tjs1983 · Saturday at 6:47 PM

I'm looking at building a summerhouse on top of a existing decking.

The existing decking has been raised off the ground, with dpc on top of the joists, then the decking boards.

I look to build a sub floor on top of decking, then the summerhouse on top.

When building this sub floor (bearers), would you insulate this with celotex, then put the summerhouse floor on top?

Thanks

jj4091 · Sunday at 5:39 AM

Personally I don't think that sounds to be such a good idea. You may have problems with it taking the weight and won't have access to maintain the decking in the future

StephenStephen · Sunday at 7:29 AM

Is there dpc below the joists?

tjs1983 · Sunday at 8:09 AM

The framework for the decking is currently raised off the ground, with pavers, then dpc with the timber on the dpc. Joists are 400mm apart with noggins.

I wasn't sure whether the decking should be removed and put summerhouse on top of current framework.

If I have to then I suppose you insulate the floor with 50mm celotex, and foil tape the joins, then the summerhouse bearers, then rest of the summerhouse?

Or if decking stays in place, place bearers on top of decking, then summerhouse on these, insulate, then floor?

chun · 2026-06-25T07:51:39+0100

tjs1983 said:
The framework for the decking is currently raised off the ground, with pavers, then dpc with the timber on the dpc. Joists are 400mm apart with noggins.

I wasn't sure whether the decking should be removed and put summerhouse on top of current framework geometry dash.

If I have to then I suppose you insulate the floor with 50mm celotex, and foil tape the joins, then the summerhouse bearers, then rest of the summerhouse?

Or if decking stays in place, place bearers on top of decking, then summerhouse on these, insulate, then floor?

I would not recommend placing a summerhouse directly on decking boards. Decking boards are designed as a walking surface, not as a structural foundation for a building. They can flex, trap moisture underneath, and make it difficult to keep the summerhouse level over time.

tjs1983 · 2026-06-25T18:47:44+0100

chun said:
I would not recommend placing a summerhouse directly on decking boards. Decking boards are designed as a walking surface, not as a structural foundation for a building. They can flex, trap moisture underneath, and make it difficult to keep the summerhouse level over time.

Totally get decking board are for light traffic, but framework below decking is sound and strong. The summerhouse would be raised off the decking to create air flow, and the bearers will be screwed through the decking into the joists below, so the decking boards wont be used for support as such? Decking boards would be sandwiched between the decking joists and the summerhouse joists (bearers)

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Summerhouse

tjs1983

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StephenStephen

tjs1983

chun

tjs1983

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