I want to build an attached 2 car garage with an upstairs two bedroom suite. My house is a rancher and it's on a lot that allows for a secondary suite or duplex. On one end is an already existing single car garage and I have enough allowable room beside it to expand another 21 feet for a three car garage. My plan is to have the suite above all three garage spaces, removing the roof over the existing garage and putting an i-joist floor in. One problem I don't know what to do with is the original house is from 1959 and is of 2x4 construction but new codes pretty much call for 6" exterior walls to use r-24 insulation. Do I need to upgrade the existing garage walls to 2x6 construction or is there another way to do it?
Hey, Doug, to add a living place above a garage you will have to go right down to finding out if your foundation and footing is able to handle the load of the new part that you want to add so I am thinking that you will have to take the existing garage down to fix that problem first but to answer your question yes it is a good idea to change or sister up to a 2x6 wall
This is a question for an engineer or designer. Like mentioned an engineer will calculate the load and whether the wall, footings and spans are all adequate.
It's best to involve them earlier rather then later so your costs can be clearly outlined.
Regards,
Tom
Hi,
You will need an architect and engineer to put plans together for you.
I would excavate a small area and be sure your foundation is suitable for the construction you desire. As well as availability for running all water sewer and electrical.
And yes the existing walls will have to be brought up to 2x6's.
There is no science spending the money to build what you have in mind unless you do it properly. I always over build.
Good luck with your project.
Regards,
James Fram
I agree with the other respondents regarding the existing garage foundation. You haven't said whether it's pile and grade beam or other (strip footings). In any event it will be necessary to ensure its adequacy to support an additional storey first. 2 x 4 is permitted to support a 2nd storey provided the spacing is no more than 16" o/c however it may be best to beef it up. If the garage is remaining a garage and will be unheated it's possible the studs can remain as is. Of course spray foam is also an option if it is necessary to achieve R-20 in the exterior walls.
Hi Doug - Typically garages do not need to meet insulation values if they are unheated spaces - check with your local jurisdiction to confirm. In regards to making a 2x4 wall comply with current energy requirements - you have options including, packing out the 2x4 to get thickness of a 2x6, or consider the use of exterior insulation. Again your local jurisdiction should be able to work with you to find a suitable solution - they may not necessarily require existing construction to be brought up to current energy/ insulation requirements.
Well the current garage/laundry room has a perimeter 16x8 concrete footing with concrete brick foundation and 10' high 2x4 walls. I'm not sure how thick the slab is but after 60 years there isn't a single crack in it... Safe to say it's thick enough. The garage is currently 14x28'... Total expansion will be 35x28'. So 2x4 16" O.C. walls, fibreglass batt insulation with 2" of foam on the exterior should meet code in regards to insulation I think.
Thanks for the added info. The footing may be adequate depending on the soils; from your description (no sign of cracking and assuming also movement of any kind) it may be OK.
The maximum height for 2 x 4 @ 16 centers is 3 m - slightly under your 10' height; your municipality may allow doubling up the studs as an equivalency or allow you to rip lumber into 2" wide pieces to increase the studs to 5 1/2". If the garage is remaining unheated, the existing 2 x 4 construction should suffice with respect to insulation. Adding rigid insulation to the exterior is a good idea to reduce thermal bridging..
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