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Having Addition built- question on footings

12K views 1 reply 2 participants last post by  AtlanticWBConst. 
#1 ·
Hi all-

Not strictly a DIY, admittedly, although I am being attentive and interested in the construction process.

We are having an addition built onto the back of our home, replacing an enclosed patio/sunroom. The old sunroom was aluminum and sliders, and has already been removed. The old room was constructed on a square concrete slab, 14'x14'. The new room will be built without removing this old slab, but will be 16'x16'. The new room will be a standard living space, built with studs, drywall, with new vinyl windows, a slider and a fiberglass entry door.

Our contractor says he can construct the room essentially like a deck. He dug 4 holes for what he called footers, but I think are more accurately called piers (correct me if I'm wrong). These holes are deep enough to be below frost, and are just to the outside of the concrete slab. so the room will attach to the house (obviously) and then be built on the beams on top of these piers, as well as supports on the existing slab, as I understand it.

My well-meaning and well-informed Father-in-Law does not think this is acceptable for such a room. He wants me to press the contractor to make an old-fashioned 3-foot continuous footer.

I'm a grown man with kids of my own, but I feel like a kid myself as I try to make sense of 2 different techniques for footings! My township's building inspector will be visiting Monday to inspect the work before the contractor pours concrete, so I guess I'll get at least the town's requirements, but I'd love to get some info from any of you all who are knowledgable. Thanks for anything you can share.
JC
 
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#2 · (Edited)
I can't comment on the exact design layout of how he is doing it. What I mean is: in terms of the number of "pier footings" being used for the layout, how he is designing the framework, attaching to the home, etc...

Hopefully the town will properly evaluate his plans.

But to answer your question about using "pier footings" or constructing a "Freezewall" style foundation (typically what is found):
The pier footings that he is using (as long as they are properly dimensionalized (depth and diameter) can be perfectly adequate. He needs to make sure that the bays between the floor joists are properly insulated. He should use rigid foam, and make sure that the area is properly sealed, etc, etc...

To Clarify, regarding this question:
My well-meaning and well-informed Father-in-Law does not think this is acceptable for such a room. He wants me to press the contractor to make an old-fashioned 3-foot continuous footer.
Small room additions are built all the time using concrete pier footings. The reasons are many. They include cost savings (Cost effectivness). We have built them this way ourselves. We have even built them this way - from architect designed and engineer approved plans.
 
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