# Detached garage



## Peach1303 (Sep 5, 2021)

Hi all-

New to the site here and trying to get some clarification.  I am planning on adding onto my detached garage (currently 24x24, looking to make it 24x30).  I have emailed the company that my town subcontracts for inspections and can get zero answers to my questions.  The only thing I can find is that they have adopted the 2015 IBC.  Does anyone know what they require for foundations/footings?  I was wanting to just do a trench pour, but I cant find anything exact when it comes to width.  Also, the frost line by me is 42", but it looks like 12-18" might be ok for an unheated detached accessory building.  Just wanting to get some thoughts before I submit plans.

Thanks


----------



## bill1952 (Sep 5, 2021)

Under IRC, it's interesting because under 600 sq ft (assuming light framed construction) you don't have to be frost protected but you addition will push you over that.

So following the prescriptive requirements and assuming decent soil, a 12 x 6 inch footing at or below frost line and stem wall, poured or block probably, for over 600 sq ft. If current garage foundation is not frost protected, I'd ask for a variance to do addition same.  Makes no sense to do deep footings if present doesn't have them and can't imagine asking to add them to existing.


----------



## Katy.Kjelvik (Sep 7, 2021)

Peach1303 said:


> Hi all-
> 
> New to the site here and trying to get some clarification.  I am planning on adding onto my detached garage (currently 24x24, looking to make it 24x30).  I have emailed the company that my town subcontracts for inspections and can get zero answers to my questions.  The only thing I can find is that they have adopted the 2015 IBC.  Does anyone know what they require for foundations/footings?  I was wanting to just do a trench pour, but I cant find anything exact when it comes to width.  Also, the frost line by me is 42", but it looks like 12-18" might be ok for an unheated detached accessory building.  Just wanting to get some thoughts before I submit plans.
> 
> Thanks


Call the jurisdiction's planning & zoning. The addition to your detached garage needs to be approved by them first. Their may be a local ordinance with restrictions for easements, building area to lot size, etc specific to your property.
Also - try calling or going into where the city hall is located. Not everyone emails effectively.
Good luck!


----------



## Pcinspector1 (Sep 7, 2021)

Zoning ordinances may control the square footage of accessory buildings, you could be limited to the size of a building? There may be other requirements beyond the building codes like a set back from property may need to be met. The community may have a zoning czar to contact.


----------



## Peach1303 (Sep 17, 2021)

So I finally got a hold of them…not easy.  They said a 12”x12” trench footing with 4” slab on top.  I don’t know if I need a footing that is adjacent to the existing garage wall…they did not specify.  So I think what I’m going to do is actually make it 20’ wide by 6’ depth (come in two feet from each existing corner).  I plan on splitting that in half to utilize as storage and a workshop, so each area would be 10’x6’ approx.  Are 2x8’s acceptable as joists and rafters 16” OC typically?  I would be putting in a wall down the middle so my plan was to utilize 12’ long 2x8’s as the ceiling joists and then 14’ rafters.  My area in Illinois 25 lb snow load.  Or, would 2x6’s be appropriate since it’s more of a shes type structure.  I will ask the building Dept, just trying to get ideas.  Thanks


----------

