Supporting interior walls on ground level

[GalileoG]

Hello all,

What is typical practice when it comes to supporting an interior load bearing wall...does it sit directly on top of the grade beam with a slab on grade stopping at each face of the grade beam or does the slab run over the grade beam and the wall sits on the S.O.G? Does it differ at door locations?

Thank you!

Clansman

If a builder has built a house for a man and has not made his work sound, and the house which he has built has fallen down and so caused the death of the householder, that builder shall be put to death." Code of Hammurabi, c.2040 B.C.

 

[ToadJones]

For interior load bearing walls in a residential setting I prefer to have a footing with a 4" or 6" block (8" tall) running under the wall and the slab poured up to the block on either side. This gives the wall a nice level base from which to be built (slabs are rarely level and that can cause problems on subsequent floors). This also keeps framing up from the slab a few inches.

 

[ToadJones]

this is what I like to do for a load bearing wall in a residential basement....This is how I did my own home.

 

[MiketheEngineer]

Same idea - but some builders like to pour a "thickened slab" in this area. Might be as much as 18'' deep and 24'' wide but gets done at the same time as the slab is poured. Cheaper!!

 

[csd72]

Personally I would do it as mike the engineer has suggested.

quicker
less ingress of moisture
it is also stiffer.

That said, the amound and type of insulation under the slab sometimes dictates the detail.

 

[ToadJones]

I have one Major problem with the thickened slab and it is not structural.
Few concrete finishers are able to get slabs perfectly flat or even close.
If one is building a load bearing wall that is "up and down" with the variations in the floor and the framing contractor doesn't cut every stud to ensure the top of the wall is flat, the the problem can propagate right through the structure.
If the concrete contractor takes the proper steps to ensure a nice flat pour, then a thickened slab is probably the way to go.
For my money, however, I go with the block as the masons will string the course in order to make sure the course is perfectly level and straight. As I mention before, if in a garage type area that may be getting wet/moisture, it is nice to have wood or metal framing up off the floor a few inches also.
I won't deny that the thickened slab is the cheaper alternative.

 

[ToadJones]

....one final advantage as far as residential construction goes is the load bearing wall can be built prior to pouring the slab.
Usually the framing contractor is the second guy on the job and having the slab pour often means that the plumbers and sometimes electricians will have to have all their installations in place prior to the framer starting. This can lead to mistakes if the plumbers and electricians don't have a good set of plans.

 

[msquared48]

For a strip footing, I would use a thickened slab if at all possible. Better integrity, and a possibility of one less pour for the job.

Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask

 

[asixth]

I have seen the detail done both ways, my preference is to pour the slab first and then build the wall.

 

[Ron]

I would go with the thickened slab as well. It is easier to control the flatness of a floor slab than the top of a footing or grade beam.

Yes, slab flatness is a construction issue for the framer. Be tough and make the finishers do it right.

 

[rowingengineer]

While I don't disagree with the advice to this point as assuming a bonded grade beam/slab construction, I do have to ask, what is the slab? Is this a floating slab, slab and beam, or something completely different? Reason is; if the slab is floating, you wouldn’t want to tie it into the wall at one point while floating the rest.

An expert is a man who has made all the mistakes which can be made in a very narrow field