Garage Slab & Basement Foundation Wall
Garage Slab & Basement Foundation Wall
(OP)
I have a situation. In a residential house, two sides of the garage slab are located right next to the 8’ high basement foundation wall. I was wondering if I should do anything to make sure there is not a lot of lateral load being transferred to the basement wall. Is there any standard detail for a situation like this? Should I step the wall footing?
Thanks in advance.
Thanks in advance.





RE: Garage Slab & Basement Foundation Wall
http://www.krmconsultants.com
RE: Garage Slab & Basement Foundation Wall
RE: Garage Slab & Basement Foundation Wall
http://www.krmconsultants.com
RE: Garage Slab & Basement Foundation Wall
Thanks again.
RE: Garage Slab & Basement Foundation Wall
RE: Garage Slab & Basement Foundation Wall
http://www.krmconsultants.com
RE: Garage Slab & Basement Foundation Wall
The detail at the top of the wall is a bit tricky but you are doing all this work at ground level not in a 10' excavation (with associated digging shoring e.t.c.).
I have even used a similar detail on industrial slabs with forklifts.
That is just my opinion.
RE: Garage Slab & Basement Foundation Wall
RE: Garage Slab & Basement Foundation Wall
The result could be a basement full of mud and concrete slabs.
I'd even keep compactors 2 feet plus away from the wall.
RE: Garage Slab & Basement Foundation Wall
Most direct way to avoid this problem is to thicken foundation wall (garage slab side) to form a ledge for supporting slab. Ledge to be 4 inches wide. Load from slab is then distributed directly down to footing (which must of course be widened). Slab must be designed to "span" between foundation wall and firm soil well beyond backfill zone (recommendat minimum "bridge" distance to be 6 feet).......Nominal reinforcement (#4 bars or WWF at center of 6 inch slab) can be adequate......though better design solution is simply to thicken slab within the "bridge" zone, to at least 8 inches for residential garage use.
If slab is "floating"......butts up to foundation wall.....then the wall must be buttresed (with adequate number of piers) or designed to resist lateral pressure (soil + surcharge). This will generally require reinforcement of concrete block wall (vertical rebars). However, as with any foundation wall that must resist lateral pressure, lateral bracing at top of wall is essential for proper design and performance.
Therefore, the increased wall thickness solution ends up being most effective......next "best" is likely "brace-piers" spaced about 6 to 8 feet (depending on wall & soil height). Both of these design solutions minimize lateral force that must be resisted along top of wall.
For concrete block wall (even with brace-piers)...12 inch thickness is highly recommended.
As with any lateral pressure conditions, a concrete wall has much better resistance......since concrete can of course resist lateral pressure in two directions. However, reinforcement / bracing may very well yet be appropriate unless increased wall thickness (to form ledge) is used.