Foundation Wall Footing Question

I received the plans from my builder for my single car attached garage and noticed the footers do not butt up against the existing foundation. They stop a few feet short. What is the reason for this? How can I have a foundation wall in those areas without footers to support them?

 

So obvious question, did you ask the builder?

 

Gotta say, I've never heard of that before.

Is the existing wall a basement wall? Generally you don't want footings stopping in the middle of basement walls because it puts lateral (side) pressure on the basement wall that the wall wasn't designed to take. Around here we step the new footing down to meet the existing footing.

Let me know what your builder says.

 

I think your builder will say exactly what Bruce H said, lateral forces being isolated/separated.
I didn't know this but the explanation makes sense. The addition will have footings enough and the 2' separation is what I would call a cantilever and maybe intended to give a little.

 

Could also be that the GC is concerned about the footing being in backfill from the original foundation wall. Although he's still going to have to somehow get the new foundation wall over to the existing wall. Like Brian said, maybe some kind of cantilever?? Are there frost concerns in VA?

 

I haven't asked him. It's the weekend and he'll be on vacation all next week. It was my understanding that the footer would have to be stepped down to the existing foundation, but it doesn't appear that is what he is going to do. A cantilever is acceptable?

 

The apparent cantilever is four feet. Seems like a lot. Not much load on either one though.

 

I wouldn't cantilever it if it were me; just keep it simple and step the footings down to the existing footing. That way there's no wondering if the cantilever was properly designed.

 

That sounds ideal, but it isn't up to me. This is what the builder gave me, and his engineer/architect signed off on it. There are quite a few details that aren't present in the drawings. For example, it mentions nothing about how they are going to tie the new foundation into the existing one, no mention of supporting the rear wall of the garage on the left side (assuming there will be a beam that is supported on the left side by the existing foundation), nothing about how they are going to support the right exterior wall after they cut an 8' wide hole in it, etc, etc. Maybe there are more detailed plans that he provides to the contractors that aren't needed by the county to obtain a building permit?

 

Also no grade beams under the slab, which three other builders recommended.

 

I would just trust the builder. I don't know the details of your area but the drawings were approved by an architect and will probably be approved by the city.

The city, at least around here, will most definitely require detailed drawings. The contractor usually doesn't share those drawings with you because it's technical and most customers just want to see an overall design.

 

No question, it's a first for me. But it has the appearance of being professionally designed; for all I know, that may be common practice in VA. I would say that if it's been designed and drawings signed by a licensed architect or engineer, you're OK.

Just an FYI, I learned a LOT over the years as an architect about construction means and methods by asking questions of the engineering consultants and contractors. I just made sure I didn't come across as challenging them, but rather wanting to learn from someone who knew more than me.

 

These are the drawings he gave me to take to the county (I am pulling the permits), so I'm assuming they are good to go. I'm curious to see how things are done when the time comes.