Detached Garage Foundation

[flobee1]

I am getting ready to build a garage detached one story 24'WX30'L. I called to get the local building code (Toledo, OH) on the footer and foundation depth. The man that I spoke to told me that with a garage my size with the floor and foundation and footer poured at the same time with wire mesh the footer only had to be 12" deep. The frost line in this area is 36" deep. I would like to go just 12" because the cost of concrete in this area is around $80/cy, but will the foundation hold up? I was also thinking about drilling 8" holes 3 1/2' deep every 3 or 4 feet to act as piers for the foundation to rest on. Would this help or is it just a waste of concrete and time? Any input would be appreciated.

[Rich]

A monolithic slab on grade is an acceptable method - it's done all over the country. It ends up being more of a thickened slab than a footer.

[flobee1]

Thank you for your help. Do you think the piers would be over kill and a waste of money?

[Rich]

Without going down to some type of bedrock material it would pretty much be a waste of money.

[Rich]

I guess I shouldn't say a total waste of money as you will get some bearing relief from the friction between earth and pier.. but in my opinion not enough to warrant spending the additional money.

[flobee1]

Thanks a million Rich.

[mjpliv]

The county/municipality is recommending the use of mesh only in this slab. If you add the free cast piers, any support they offer will only serve to fracture or distort the slab because there is not enough (any) rebar to support the concrete between piers. Using a welded wire mesh does not add much in the way of structural value to a slab.

If the monolithic slab/footings are designed as grade beams (the services of an engineer are required for this) then the piers are redundent anyway.

[mjpliv]

Provide frost protection in the form of rigid type II insulation to the edges of the foundation and 2 feet outward from the base of the footings (slope down and away from).

[flobee1]

Thanks mjpliv, I was worried about frost. How should I attach it (ie..Masonry nails, or an adhesive, or will the dirt simply hold it in place?)You and Rich are the answer men. Thanks again to both of you.

[mjpliv]

Pour in place 1/2" X 8" anchor bolts on the wall plate center line at 4 feet on center. Remember to not install bolts at your garage door openings or man door openings. You will want extra bolts about 6" from ench door opening (unless that falls on a 4 foot center). Drill your bottom plate (11/16") and install with sill gasket (available in rolls at your building supply) between the concrete and the plate. Use washers and nuts to secure the bottom plate. About 2-3 weeks into the project, re-tighten the nuts because the botom plate will shrink.

[Rich]

For attaching the insulation - you can use a polyurethane glue (PL400) until it's backfilled.

[mjpliv]

I swear to god that when I saw that last request I though we were being asked about attaching the wall plate. Talk about a brain fart! :oops:

I gotta start reading the questions more carefully. flobee1 must be thinking "What the hell is this guy talking about!".

:D

[Rich]

haha. I was going to mention something.