Planning for a garage addition, is this possible?

[garagelogician]

I have a smallish 3 car garage (about 27-ft wide x 19-ft deep), I would love to add onto it to provide more space for workbenches/cabinets/etc and to add a little more breathing room to make the 3rd stall more functional. I can't extend out the front, because it is already at the front setback line. The house is behind (and about 5 feet of the upstairs extends over it), so I can only extend about 4-ft on the right side, and behind the 3rd stall about 6-ft.

I don't know much about the framing above the garage (all sheetrocked and no access hole). I assume they are trusses. Roof pitch is 6/12, and I'm in MN so we have snow loads to deal with. There is a girder truss that transfers the load of the upstairs bedrooms to a spread footing at the current side garage wall. Without some further engineering, I'm assuming I'm going to have to keep a post in this location (which shouldn't be a deal breaker for how I am going to use the space).

Current ceilings are about 10'-5", and I won't need that headroom in the addition, so keeping the current roof pitch is okay. Problem with that is that I need a 4/12 pitch on the addition out the rear of the garage, to keep it below an upstairs window. Any thoughts about transitioning the roof pitch?

I know next to nothing about home construction or framing, but does this seem doable? Any ideas on what I should request from a contractor?

Lot cert with proposed footprint:

Existing front elevation:

Modified front elevation with 6/12 roof:

Modified front elevation with 4/12 roof:

Side and rear elevations:

Existing foundation plan:

Existing framing plan:

Section view through house/garage/foundation:

Picture of the front of the house when we moved in 2.5 years ago

 

[Radix2]

I think you have the idea well in hand, the issue will be it will be really expensive for adding only 150 sq ft. You would put in a beam to hold your current trusses and add from there. Might need several posts to keep the height of the beam down.

I'd keep the 6/12 pitch, build some detail in the back to accommodate the window, like turn the corner with a hip.

 

[garagelogician]

I think you have the idea well in hand, the issue will be it will be really expensive for adding only 150 sq ft. You would put in a beam to hold your current trusses and add from there. Might need several posts to keep the height of the beam down.

I'd keep the 6/12 pitch, build some detail in the back to accommodate the window, like turn the corner with a hip.

It may be only 156 sqft, but that is still a 30% increase in floor space. I have no idea what the cost will be, but am hoping to do the finish work myself to save a few bucks.

The previous homeowner had plans drawn up for an addition to the house that included the 6ft extension out the back of the garage, but did not include the addition out the side. Those plans showed a 4/12 pitch for the addition. I wonder if I could hold the 6/12 out to the extent of the current garage, and then transition to 4/12 for the last 6 feet.



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[matt_i]

Big money could be spent depending on how you access the new addition at the right of the garage. If its a man door into the space and most of the right-side exterior wall stays intact but just becomes an interior wall, then probably not bad.

However, if its intended to be clear-span or with 1 post at the girder, then the project has crept into a huge resupporting of the outside wall which is load bearing for the attic/roof above, and trying to develop shear resistance for the supports.

Imo you want the same exact foundation as the rest of the build so it all resists movement the same way. So this is going to be a dirt + concrete project as well.

Any project which interfaces with existing, finished work is an extra pain for any builder due to the very detailed planning and "fitting" of surfaces and features. A 1999 build is very likely to have some materials unavailable to purchase (obsolete, discontinued) for matching.

It wouldn't surprise me to get bids of $15k for the project, $30k wouldn't surprise me for the clearspan/1-post option in the framing.

 

[rsanter]

Yes it can be done. If,you want clear span it will be very expensive. To,gain clear span you will have to,replace the two,sections of walls as well as the roof over the garage.

What you may be able to do is replace the exsisting walls with a series of posts to,support the exsisting roof and then add on from there

 

[garagelogician]

Any project which interfaces with existing, finished work is an extra pain for any builder due to the very detailed planning and "fitting" of surfaces and features. A 1999 build is very likely to have some materials unavailable to purchase (obsolete, discontinued) for matching.

It wouldn't surprise me to get bids of $15k for the project, $30k wouldn't surprise me for the clearspan/1-post option in the framing.

$15-18k would probably be doable for me, any more than that probably isn't worth it. Shouldn't have any matching issues, siding/stone veneer is only 3 years old and I just had the roof replaced due to hail damage.

Yes it can be done. If,you want clear span it will be very expensive. To,gain clear span you will have to,replace the two,sections of walls as well as the roof over the garage.

What you may be able to do is replace the exsisting walls with a series of posts to,support the exsisting roof and then add on from there

Thanks for your input. I can definitely deal with a row of posts in this area, clear span is not necessary for my needs in this case. It would be nice, but not when it breaks the budget.

Anyone have a general rule of thumb for post spacing? Can they install some sort of header/beam to support several trusses?

 

[Radix2]

$15-18k would probably be doable for me, any more than that probably isn't worth it. Shouldn't have any matching issues, siding/stone veneer is only 3 years old and I just had the roof replaced due to hail damage.



Thanks for your input. I can definitely deal with a row of posts in this area, clear span is not necessary for my needs in this case. It would be nice, but not when it breaks the budget.

Anyone have a general rule of thumb for post spacing? Can they install some sort of header/beam to support several trusses?

Haven't the time to run the software, but considering you have 10 foot ceilings, you should be able to easily get by with a beam supported at the front, the back and one in the middle, so 12 foot or so openings to your benches, with 8 foot or more headroom.

 

[HoosierBuddy]

Wow.

It looks super hard (expensive) for what you'd gain.

1. How far off the side lot line does that leave you and what is the required setback?

2. Are there any utilities buried on that side you will have to contend with?

Phil

 

[garagelogician]

Wow.

It looks super hard (expensive) for what you'd gain.

1. How far off the side lot line does that leave you and what is the required setback?

2. Are there any utilities buried on that side you will have to contend with?

Phil

Verified with the city today that the min. setback is 5-ft. This addition would be 6-ft at its closest point, so I could possibly bump it out another foot...right to the setback line.

No utilities. I would have some sprinkler lines to move, but that is it. Excavation could get close to the property line, but we are getting to be good friends with our neighbor on that side...so I don't think we'll have any issues there.

I agree that it is a lot of hassle and expense for a paltry 150'ish sqft...but that is the limits that I have to work within. We love our house and our neighborhood...and we would have to move too far out to be able to afford what we really want (which would put me even further from work). I can't say we are going to stay here forever, but I'm sure it is going to be for at least the next 15 years. I will be in my 50's by then...and I would really like to be in a garage space that works better for me until I can move on to a bigger and better space. It is not a lot of room, but it would at least give me some more work/storage area which will make the rest of my space that much more usable.

 

[ace10]

Depending on what you want to do with the right side (as viewed from street) roof load, this could get pretty darn spendy.

If this was in my area of the country, it's probably approaching a six figure project if hired out. Just the masonry (site prep/point load footing/foundation/slab/veneer) would be far more than $15k.

 

[NUTTSGT]

Before I got too far into this project, I'd gain access to the garage attic and see what your roof structure is. See if you have trusses or rafters and where are the rafters sitting.

It appears you have a separation wall between the two garage halves. If the separation goes up to rafters and the full height, this may save you some bucks if it can be incorporated into a new roof line and it's supporting structure.

 

[CraigStu]

Would there be any use doing a deeper addition just at the rear? That would avoid the expense of figuring out how to replace that right side outer load bearing wall. like this
Untitled by craig stuard, on Flickr
Not sure of this detail, but possibly lower the roof line of the addition, but keep the pitch the same as the existing roof. Start w/ whatever height you need to barely clear the bottom of that upper window and draw the roof line out as far as setbacks will allow. Could be that the outer couple of feet of the addition do not have a full height ceiling (think Cape Cod house second floor rooms) but putting a work bench there would still be usable. I 'think' the window on the first floor is a bathroom so just eliminate it if wife will allow. Only mod to the existing structure would be an opening in that rear wall to access the addition. That is easy to do.
Another option, still only adding on to the rear, would be to make that second floor window smaller. There could be code requirements to deal with but, if code allows, the actual job is pretty easy. That would allow you to match the existing roof height and pitch and again your outside wall could be further toward you neighbor than the existing wall.

 

[garagelogician]

Would there be any use doing a deeper addition just at the rear? That would avoid the expense of figuring out how to replace that right side outer load bearing wall. like this
Untitled by craig stuard, on Flickr
Not sure of this detail, but possibly lower the roof line of the addition, but keep the pitch the same as the existing roof. Start w/ whatever height you need to barely clear the bottom of that upper window and draw the roof line out as far as setbacks will allow. Could be that the outer couple of feet of the addition do not have a full height ceiling (think Cape Cod house second floor rooms) but putting a work bench there would still be usable. I 'think' the window on the first floor is a bathroom so just eliminate it if wife will allow. Only mod to the existing structure would be an opening in that rear wall to access the addition. That is easy to do.
Another option, still only adding on to the rear, would be to make that second floor window smaller. There could be code requirements to deal with but, if code allows, the actual job is pretty easy. That would allow you to match the existing roof height and pitch and again your outside wall could be further toward you neighbor than the existing wall.

Knowing my wife, and with how dark that end of the house is anyways, removing the bathroom window will probably be a non-starter. We also use that window a lot to get a cross-breeze in that level of our house when the windows are open. Also complicating matters is that there is a retaining wall about halfway between the windows on that side of the house (see attached). Granted, it is probably cheaper to regrade and change/eliminate that retaining wall than it will be to mess with the current load-bearing garage wall. I could only extend out the back and make that addition 6x13, but I'm thinking it might look goofy from the front of the house?

Another reason I wanted the extra width is that I am planning to have a 4 post lift that will live in that bay (for utility trailer storage above a 3rd car), but that can be rolled over to the middle of the garage for bigger projects. The extra width would be nice to make the lift more usable in that bay, at least for quick oil change jobs/tire rotation/etc.