Foundation Blockout for Garage Doors
Foundation Blockout for Garage Doors
(OP)
I'm trying to determine which is the preferred method of blocking out a stemwall foundation for garage door where a slab will be poured in the garage as shown in the images below. I've seen it done both ways and I've actually drawn details showing both these options. Option 1 does not typically block all of the stemwall out and seems to be more common in locations where the frostline is deeper (24" or deeper, ie. Utah). Option 2 completely blocks out the stemwall at the garage door and then a thicken edge is poured where the slab meets the footing at the garage door (this seems to be the preferred method in Western Washington). From a structural point of view which is the better method and also from a construction point of view what are the pros and cons?
Option 1:

Option 2:

View model here:
https://3dwarehouse.sketchup.com/model.html?id=905...
A confused student is a good student.
Nathaniel P. Wilkerson, PE
www.medeek.com
Option 1:

Option 2:

View model here:
https://3dwarehouse.sketchup.com/model.html?id=905...
A confused student is a good student.
Nathaniel P. Wilkerson, PE
www.medeek.com





RE: Foundation Blockout for Garage Doors
A confused student is a good student.
Nathaniel P. Wilkerson, PE
www.medeek.com
RE: Foundation Blockout for Garage Doors
RE: Foundation Blockout for Garage Doors
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
RE: Foundation Blockout for Garage Doors
Option 3:
A confused student is a good student.
Nathaniel P. Wilkerson, PE
www.medeek.com
RE: Foundation Blockout for Garage Doors
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
RE: Foundation Blockout for Garage Doors
I have shown Option 3 but given the 24" stemwall and the 12" projection of the stemwall above the 4" slab it would seem more practical to go with Option 2.
A confused student is a good student.
Nathaniel P. Wilkerson, PE
www.medeek.com
RE: Foundation Blockout for Garage Doors
Why the 12" projection? Around here 8" is typical.
RE: Foundation Blockout for Garage Doors
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
RE: Foundation Blockout for Garage Doors
RE: Foundation Blockout for Garage Doors
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
RE: Foundation Blockout for Garage Doors
I agree that although we complain about our deep frost depths constantly, they sure then themselves to beefier foundations. Perhaps we should stop complaining.
RE: Foundation Blockout for Garage Doors
RE: Foundation Blockout for Garage Doors
In this particular case I would not portal frame (PFH) it since my aspect ratio is 3.33 and is less than the 3.5 maximum requirement by the SDPWS. I would just use two segmented shear walls on each side of the door.
The one flaw with portal framed walls is the hinge created at the header and pony wall, that is the reason for the limitation on the pony wall height, at least that is my understanding of the rationale behind the IRC/IBC on this matter. Other engineers hate these things and strongly prefer a conventional shear wall (segmented) design. Moving the header to the underside of the top plate certainly helps but there is still a hinge issue between the header and the portal frame shear panel which is a weakness for out of plane loads (ie. wind perpendicular to the wall).
I would certainly argue that a conventionally framed header with two shear panels is better, but most designs I encounter don't have the wall length that allow for it.
The one positive of the portal frame is the reduction in the holdown forces. I wasn't able to fully quantify this until I created my portal frame spreadsheet/calculator but it is significant.
A confused student is a good student.
Nathaniel P. Wilkerson, PE
www.medeek.com
RE: Foundation Blockout for Garage Doors
Based on Terry Malone's book I've written a spreadsheet for looking at the overturning, shear and moments in the foundation at locations like this where there are concentrated shear wall loads. A lot of these designs don't work, they fail, you really do need a better grade beam. The problem is the designers and local contractors push back really hard when I get too creative with this stuff.
A confused student is a good student.
Nathaniel P. Wilkerson, PE
www.medeek.com
RE: Foundation Blockout for Garage Doors
The spreadsheet is here:
http://design.medeek.com/resources/shearwall/2016-...
PDF preview:
http://design.medeek.com/resources/shearwall/2016-...
Any feedback or corrections are much appreciated. My comfort level with concrete is still not where I would like it to be.
A confused student is a good student.
Nathaniel P. Wilkerson, PE
www.medeek.com