Garage Addition footings & foundation

[Conner]

I've seen some folks here with similar projects, but no one with the same particular question as me.

I'm planning to build a garage addition onto the side of my home. Existing house foundation has 8" block walls over 16" poured footings and garage will have the same. The garage footings will be the same depth as those for the existing house.

Since I'm planning to build the new garage wall right against the exterior wall of the old house, half of the new garage foundation wall will actually fall over the outer edge of the existing house footing and the two foundation walls will end up being right against one another. Maybe a picture will help. The existing foundation is on the left and the proposed garage foundation is on the right (although they are drawn like poured walls the walls actually are/will be block):

http://www.mydatsunroadster.com/misc/garage_foundation_pic.jpg

How wide should the footing be for the new garage foundation wall that is right up against the existing foundation wall. How should I tie the new footing into the existing one? Also, should I do something to tie the new garage block foundation wall into the old one? I'm worried about water getting between the two block walls and freezing and forcing them apart and/or the house and garage settling at different rates.

Thanks in advance for any guidance anyone can provide!

Andy Conner

[Conner]

Okay, I realized that I overcomplicated this a lot.

The garage I am building is adapted from an 84 Lumber detached garage kit that I am essentially going to build up against my house (which, BTW originally was an 84 Lumber kit house). But I've decided to just omit the adjoining wall from the garage so there won't be double frame or foundation walls or footings; I'll just be building three walls rather than four. To drywall the conjoined garage wall I will just go over the house sheathing and/or block wall, maybe fir out with some strips if necessary.

Well I think I have my plans modified and together, so hope to get my building permit from the county this week.