Concrete slab/wall junction for new workshop

[alan_1]

First post here so apologies if it's been covered. I'm planning to build a decent insulated workshop from the ground up but I'm stuck at the slab. I want the slab to be insulated and plan to build the timber frame off it but if I do the usual hardcore, sand, insulation, damp-proof membrane and slab, the edge of the slab will be exposed to the elements & therefore cold. See my drawing with problem area in the circle. No doubt I'm overthinking this but has anyone got a simple solution for insulating the edge of the slab?

 

[Garden Shed Projects]

Run brickwork around the perimeter on a strip foundation, then line with insulation and pour the concrete within. Kinda like this-

 

[Spectric]

GSP has the right idea, you want the floor insulated all round from below and the sides.

 

[Fergie 307]

I have built mine in similar fashion to your illustration, but I laid the slab so I had a deeper section under the walls about 12 inches wide, then the insulation in the middle, so it is sealed all round by the slab. I appreciate this is a bridge, but practically speaking I have never had any problems with damp or cold. Just make sure you do the bottom of the outside wall so water is kept away from the side of the slab. For a habitable building you would want to go the whole hog, but for a workshop I think you would be going to a lot of extra expense to address a problem you aren't likely to have. My main shop is used for vehicles so has a solid 8inch reinforced concrete floor with no insulation whatsoever, and I have no issues with damp, nor does it seem noticeably colder than the one with insulation, although I haven't measured it. And don't know how you plan to attach the walls to the slab but I use the self tapping concrete bolts. Used to be Multi Monti brand but screwfix now do their own version. They screw directly into pre drilled holes, so no expansion.

 

[alan_1]

Run brickwork around the perimeter on a strip foundation, then line with insulation and pour the concrete within. Kinda like this-

View attachment 154625

Thanks for your thoughts GSP. Definitely the Rolls Royce method but probably more than I want to spend.

 

[alan_1]

I have built mine in similar fashion to your illustration, but I laid the slab so I had a deeper section under the walls about 12 inches wide, then the insulation in the middle, so it is sealed all round by the slab. I appreciate this is a bridge, but practically speaking I have never had any problems with damp or cold. Just make sure you do the bottom of the outside wall so water is kept away from the side of the slab. For a habitable building you would want to go the whole hog, but for a workshop I think you would be going to a lot of extra expense to address a problem you aren't likely to have. My main shop is used for vehicles so has a solid 8inch reinforced concrete floor with no insulation whatsoever, and I have no issues with damp, nor does it seem noticeably colder than the one with insulation, although I haven't measured it. And don't know how you plan to attach the walls to the slab but I use the self tapping concrete bolts. Used to be Multi Monti brand but screwfix now do their own version. They screw directly into pre drilled holes, so no expansion.

Thanks Fergie, good to know your experiences. I'm not planning to live in it so (unless the wife has something to say about that!). Keen to keep the costs down too so will probably just go for it and make sure it's all kept dry.

 

[Fergie 307]

Insulation in the roof and walls is far more important IMHO. My main shed is roughly 10 x 7m. One quarter is stud walled off and is my tool room, where my machine tools and so on live. The roof joists are 8x2, and in this room I have 6 inches of insulation in the ceiling and 4 in the walls. The rest of the building only has 4 inches in the roof and none in the walls, T&G 18mm floor boards for the inner wall, membrane, battens and featherboard outside on 4x2 framing. Would have liked to insulate all the walls but simply couldn't afford it at the time. The difference in the tool room is very noticeable, and I think primarily down to the extra insulation in the roof. Even before I did the walls it was very noticeably cooler in there in the summer, and warmer in the winter than in the rest of the building. So I would prioritise your spend on that rather than being too concerned about the floor.

 

[Garden Shed Projects]

You could leave the slab cold and use the insulation on top along with chipboard or osb flooring which may be cheaper. Suppose it depends what machinery you intend to use.