Depending on the base, sealant may be required. If it is very smooth round the perimeter and to the footprint it is not generally necessary.
If the base is slightly rougher and doesn't have a polished finish, then we would recommend to use a DPC (damp proof course) under the foundation beams as these will compress down to make a tight seal
The composite beams have less give and do not compress, therefore is the base is bumpy a sealant may well be an idea.
If the base is to the footprint this is unlikely to happen, as there is no where for the water to rest when the base is done to this size.
We do also recommend that a damp proof membrane is used either on top of the base or under the base. This is not something that we supply but you should be able to source this from a local DIY store. Or if you opt for our insulation kit this will come with a DPM included.
Normally, if you are insulating the cabins floor, the DPM will be done on top of the base, dished up inside the foundation beams.
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