I am looking for input and advice from those that have been there . .
I am about to embark on a mudroom and garage addition on my house. I am subbing out the footers, foundation and slab work because I am not comfortable with doing the concrete work myself.
So far, I have two bids that I am really considering. Both include excavation, footers, foundation and slab. Both bids are within $1500 of each other so I am not really considering the price as too much of a factor.
One bid calls for block walls and the other a poured wall. The block wall bid calls for a 5″ slab without grade beams. The poured wall bid calls for a 4″ slab with grade beams. (4″ is the standard around here – I assume the standard most places)
First of all, what is a grade beam? I assume it is a concrete beam placed on concrete footers and piers to help support the slab. This is a 24×28 slab. Is this support really needed? The poured wall guy designed this as a structural slab.
Is there some advantage to a structural slab versus the 5″ floating slab the other guy is proposing?
Every where I turn I see poured walls and they seem like the most popular choice nowadays. Are they really superior to block walls?
At this point, i am leaning toward the poured walls guy even though he is the more expensive bid. But if the structural slab is overkill, I could go either way.
All I’m looking for is educated opinions. Anyone care to share?
Replies
Don't know what part of the country you're in, but around Chicago all foundations for your type of an addition would be poured concrete. The bottom of footings would be at frost line or lower (42" below finish grade). There would be a continuous keyway in the footing to tie-in withe the foundation wall. The top of foundation would be a minimum of 6" above finish grade. Depending on your perimeter wall construction above, the foundation wall thickness would be 8"-12" and reinforced with (2) # 5 bars top and bottom.The concrete slab for the garage would typically be 5" thick with 6x6 #6/6WWF reinforcing on 6 mil vapor barrier and 4"(min) compacted gravel. The slab would be pitched down towards the overhead door opening. The top of foundation at the overhead door opening and at any mandoor would be depressed 12" below finish grade so that the slab can be poured over. There needs to be a gas curb (6" high min.) between the garage and the attached house. Depending on preferences, some will also put bent bars in the depressed foundation to tie into the slab. The slab gets thickened at the depressed foundation area. Some municipalities do allow a single pour concret foundation with a belled bottom, reinforced the same. However, they would allow this only if the garage remains a single story structure with no future second story.
I know in Wisconsin a lot of foundations are done with concrete block, for garages and homes. It seems to work there quite well. No could ever give me the reason they do that, maybe cost of labor or material?