Timber build on DPC'd slab

[Jimbo37]

Your view, please (see graphic)

I am having a timber structure garage built on an concrete slab, with a pamp proof membrane below. The membrand and the slab are all comfortably above ground level. The timber soleplate and uprights are all treated. My question is two fold?

 - Do I need a DPC under the treated timber (the builder says its better not, as it can tend to hold water and offer no benefit on a dampproofed slab)?

 - I want to leave the side of the concrete slab exposed, 100mm of 200mm deep - is this wise, or should I protect from rain?

TIA, James

 

Edited August 10, 2020 by Jimbo37
Better image

[Mr Punter]

Yes, go with the DPC.

 

I would prefer to see the edge of the slab protected or coated.

 

I assume this is not insulated?

[Jimbo37]

Thanks, Mr P - correct, its not insulated. I think I'll go with the DPC recommendation, thanks. What are the main risks of leaving side unprotected?

Edited August 11, 2020 by Jimbo37

[vitessesteve]

I will interested to hear more.

 

My slab is already done.  I have a DPC under it. This is what it looks like now the shuttering is off.

 

The concrete got between the DPC and shuttering.  I will putting a DPC under the floor plate.  What should I do about the edge of the slab?

[Russell griffiths]

Cover it with some upvc facia board, anthracite colour, will hide mess and keep water bounce from penetrating slab. 

[markc]

I would definitely go with the DPC to separate timber from concrete. If your garage floor is likely to get soaked or washed from time to time i would also pack the soleplate to allow any water to run underneath. Plastic shims like the ones glaziers use are ideal. should be placed under the stud points. These are also great if the slab isn't perfectly flat.

[Jimbo37]

Thanks all, I went with the DPC under

@vitessesteveI am building a cladded timber structure, so Ill bring the clad down to within 75mm of the base of the slab. If that looks like it may getting too much damp, I'll do something along the lines of @Russell griffiths suggestion, using a cladding (composite) board instead