When to tie the S.O.G to FDN wall and when not to?

I typically dowel into foundation walls when the exterior element is non-load bearing like steel studs, and let it float when the boundary conditions are CMU or concrete walls.

Clansman,

It depends on site conditions.

If full compaction is not possible along the sides of grade beam or foundation walls, it is better to provide dowels and grade beam is designed to carry weight of about 3 ft(1 m) wide SOG.

Same applies for the sidewalk.

Sometimes dowels are avoided as in case of grade beam top elevation higher than SOG top elevation, to avoid bending of dowels and to avoid site hinderance until the slab is poured.

I avoid it at reasonable cost. The only time I will dowel a slab to the wall is in the case of tilt wall construction, were a pour strip is required. I do it here with the idea that I will have a construction joint located near the wall. I do it for added over turning or sliding resistance in panels with a large in plane load.

A properly designed slab on grade does not need to be connected. Slabs and walls will always settle at differing rates. Let them move independently.

Dowel though openings to prevent trip hazzards at doors.

For a basement slab I usually I prefer not to dowel the slab to the wall. One of the exceptions is when the slab resist sliding of the basement wall. If the friction between the slab and ground is insufficient, I call for dowels between the slab and the side walls.

I always connect the slab to slab diamonds of column bearing on spread footings, otherwise differential settlement can telegraph through the outline of the diamond. Usually I connect those via 2x2 shear key.

If an exterior slab bears on a substantial amount of fill and is aligned with the interior finish floor, i dowel that slab to the wall.


Eric McDonald, PE
McDonald Structural Engineering, PLLC