Control joints above strip footing

[jimtheengineer10]

Is it acceptable to install control joints in a slab above a strip footing or is there a minimum distance they should be away from the strip footing? Thank you.

 

[BAretired]

It is normal to place the slab on top of the strip footing. Control joints are usually sawcuts. They don't work perfectly, but the slab can slide as easily on a footing as it can on granular fill.

BA

 

[jimtheengineer10]

so are you saying it is ok to sawcut above a strip footing or should the sawcut be moved away from the strip footing?

 

[BAretired]

Are you talking about a sawcut perpendicular to a strip footing? If so, the saw blade can't come that close to the wall. Furthermore, it can't be moved away from the footing because usually the strip footing goes around the entire perimeter of the building.

If you are talking about a strip footing in the middle of the floor, then presumably it supports a wall. It is usual to provide a pour break and concrete curb to keep the wood dry, so a sawcut would not be used in the slab at that location.

BA

 

[jimtheengineer10]

It is a strip footing in the middle of the floor supporting a wall. There will be a p.t. sill plate installed above the slab and then the stud wall built on that. Is a sawcut acceptable here?

 

[BAretired]

I would not use a sawcut in the middle of a wall plate. If you are not going to use a curb to keep the bottom plate dry, then I suppose you could use a sawcut beside the wall but still over the footing.

BA

 

[hokie66]

Interesting. I suppose it varies depending on where you are, but I have never seen a curb built to start a stud wall. As to control joints, the location would depend on why they are being used.

 

[BAretired]

In Western Canada including Alberta, Saskatchewan and Manitoba, swelling clay soils are common. They sometimes have uplift pressures of 1500 to 2000 psf. If bearing walls are built on grade slabs, they have a good chance of heaving, so the usual practice here is to build the strip footing, then a six or eight inch high curb and the bottom plate rests on polythene on top of that. The slab is poured later, so there is a joint each side of the curb without sawcutting anything. This may not be the practice elsewhere.

Non-bearing partitions are usually built directly on top of the slab with a clearance at the top to permit movement.

BA