Halo

I have done it both ways ...rebar pinned to perimeter and slab floating not pinned to surrounding stemwalls. Garage is 16x30 with #4 on a 24" grid. Slab will be @ 5". We do get an occasional quake here in the Northwest and I am leaning toward the slab not being pinned/tied into the surrounding stemwalls. Any comments?

TIA

DBCoop

Halo,I too have done it both ways and I would not pin the slab to the stem wall....Of course a good base and compaction is the key!!! For what's worth,on a garage floor what I also do is use construction adhesive and attach 1/4 inch foam to the stem wall with with the top of the foam being slab elevation.Helps cushion the movement between the two.

Kgmz

We don't usually pin it.

But I have a story about a bunch of homes around a Cul de Sac in Federal Way, WA.

About 15 years ago we got a contract to remove and replace 6 homes garage slabs, walks, concrete porches, and driveways. These homes were built on fill, with the foundations being grade beams on caisons. I don't think they ever got the fill in the garage and around the houses compacted well enough as it was very wet there with a wetland behind the homes. Things had sunk so bad some if over 9", and some of the porches were tilted with a difference of almost a foot from side to side.

So if you are firm soil and compact the gravel under the slab you will be fine. But if there is any fill and it can't be compacted good enough pin it.

Halo

Thanks guys...

I actually asked for expansion-joint to be run around the perimeter and have been met with resistance. I believe these guys are just plain used to doing it half-a$$ed. If using EJ, how would you atatch for the pour...adhesive like mentioned above for foam?

Snobnd

I have had friends tell me it both ways.

I have seen concrete shrink and leave a little gap - when that foam gets old and moves like the expansion material used for sidewalks, gives out, it leaves a large gap.
I would rather have a small gap.
In basements here in CONN Concrete floors are done without any materials against the foundation walls otherwise the water would seep in.

Halo

My only real concern is for longevity against quakes. The substrate is solid and water is not an issue on this site. This area and particularly this home had quake damage the last go around. The floor replacement was directly because of the chimney rocking and blowing the floor out. The chimney is removed now and the space was made larger, but still trying to be pro-active. I found the foam DBcoop was refering to and will have the sub use it, Thanx.