SIP outdoor building base

[paul_1974]

Hi,

I need some advice for the foundation/base of an outdoor building:

I will be building an office/studio with a SIP kit (4.2m x 2.9m), flat roof and I cannot decide on a base. The ground is currently grass on a fairly clay soil.

Which option do you recommend sitting the SIP floor (100mm) on:

a. 150mm subbase + 100mm concrete slab base + DPM membrane (then SIP floor)
b. 150mm subbase + 100mm concrete slab base + DPM membrane + (??mm) treated timber bearers + DPM membrane (then SIP floor)
c. Ground screws with flat support fixings + DPM membrane (then SIP floor)
d. Any other suggestion?

If concrete base, do I still need to build an insulated slab or is the SIP 100mm insulation enough? If insulated base is the way, what thickness insulation/concrete?

Personally I don’t like the idea of leaving a gap underneath in case of rats nesting etc, but not sure if ventilation is a must in this case.

I am not expert, so any advice is appreciated

Thanks
Paul

 

[^woody^]

Option a. No need for extra insulation.

Bear in mind that no timber cladding should be within 150mm of ground level to avoid staining and premature rot. This normally means some brickwork to raise the panels, but it depends on how well (or badly) the kit is designed.

 

[paul_1974]

ok thanks.
I understand the 150mm rule. I am also going with cement boards cladding to try reduce that issue.

 

[catlad]

Concrete piers or a full slab will be ok ( wood and the ground = no )