Garage Extension Cost

[rc356s]

Hi Guys,

I live in santa clara county and would like to add on to my garage. It is currently 20'x20'. I would like to extended it by 12'x20'. What can I expect to pay per sq foot for this? I have spoken with a couple contractors over the phone and no one can tell me what it cost per sq foot. I am basically looking to add the foundation, the three walls, and roof. I do not need any doors but perhaps a couple windows. Any ideas what this cost?

thanks,
skipper

 

[brycez28]

You are in a different part of the country and have a different style building, but I just got an estimate for doing a 30'x60' addition to a 120'x60' post frame building, keeping the current end wall and having a doorway between the two. Building is 60' wide, needs a lot of excavation and is in a generally "wet" area. Quote includes excavation, concrete, couple doors, metal siding and roofing. No interior finishing. Walls are 12', I believe. Total came to $34,400. $11k of which was labor, $8k for concrete. Works out to about $19/sq foot.

Edit: Cost doesn't include plans, permits or fees.

 

[Falcon67]

I would imagine that in CA with their **** permitting process it could be anywhere from $40 to $140 sq/ft. Everything I've read about being built out there seems to run 3~5 times what it does around here.

 

[Zeke]

I would imagine that in CA with their **** permitting process it could be anywhere from $40 to $140 sq/ft. Everything I've read about being built out there seems to run 3~5 times what it does around here.

The permits are pretty much standard IBC compliant stuff. The costs of permits might be 3 to 5 times higher than yours but building costs are not THAT much more with the exception of roofing. Roofing contractors are expected to pay 120% of worker's wages in comp insurance. Most cheat.

I'm going to take a WAG as a contractor myself and predict $50/ sq ft.

 

[larry_g]

Without our knowing the lay of the land and excavation requirements, roofing, siding, flooring, electrical and hvac requirements anything would be a guess. Do you have any facilities like septic, power, or water to deal with? Got room on the property to dump excavated material? Rock walls that have to be blasted to make room?

So many details go into a bid that I'm not surprised that you can't get a response from a builder/contractor.

lg
no neat sig line

 

[rc356s]

Yes, perhaps with so many variables it would be difficult to give an estimate but I would think material cost would be simple. I can probably estimate how many 2x2 are needed, sq footage of 3/4" ply wood panels, etc.

It is what I believe a small project, I have been thinking of tackling it myself. What I don't know is do I need architectural blue prints or just a layout to provide the city. I do mechanical CAD drawings so I can easy design a layout that looks professional.
Layout out the foundation forms does not look too difficult other than the knowing how to place the rebar support. I know many on the site have built their own garages a 12ft extension may be do able.

 

[Zeke]

Yes, perhaps with so many variables it would be difficult to give an estimate but I would think material cost would be simple. I can probably estimate how many 2x2 are needed, sq footage of 3/4" ply wood panels, etc.

It is what I believe a small project, I have been thinking of tackling it myself. What I don't know is do I need architectural blue prints or just a layout to provide the city. I do mechanical CAD drawings so I can easy design a layout that looks professional.
Layout out the foundation forms does not look too difficult other than the knowing how to place the rebar support. I know many on the site have built their own garages a 12ft extension may be do able.

Simple plans will work but you need to show the standard details like rebar and anchors. Many building depts have handouts that you can simply staple to your plot and floor plan. In some cases you will need to show an elevation and maybe even a section showing your upper attachment details to the existing.

Don't underestimate layout and setting forms. Many concrete contractors will set forms and they have the materials on the truck to do it which they reuse. You will spend money on things like stakes that will get used once.

 

[rc356s]

Good points, many details I did not know about. This board is great!

 

[JoeFin]

I would imagine that in CA with their **** permitting process it could be anywhere from $40 to $140 sq/ft.

I'm about 100 miles north of the Op and I'm guessing mine was $60 - 65 per sq ft all told using myself with "Home Dippo Labor". Mine was a 20' x 16' extension on to an existing garage as well

Certainly up graded in many ways and fully permitted but still an expense when compared to Southern States building codes.

I added a 100 amp subpanel - 1 1/2 EMT with #2 copper feeders
6" Slab reinforced on 2' centers with 4" rock bed - (heavy machinery)
Exterior Compressor housing with 3/4 black pipe air system
40 yr roofing materials - seamless gutters
R-13 walls / R-36 ceiling
Dual pane glass, 5/8 Dura-board sheathing, 5/8 fire rock

 

[matt_i]

It is what I believe a small project, I have been thinking of tackling it myself. What I don't know is do I need architectural blue prints or just a layout to provide the city. I do mechanical CAD drawings so I can easy design a layout that looks professional.

I would argue to spend more time on the drawings up front, if you are going to do the project, as it will pay off later. If detailed and updated to match "as built" changes, it can really speed things up if you are doing the construction yourself. In other words, the building department likely does not care down to the last nail about your garage. They would like to know where on the property it will be built, what it will look like at the end (from a black and white wireframe viewpoint) and how much it cost, so they can assess the proper taxation increase.

I did my drawings on D sized paper, prints made at kinkos from .pdf conversions. 3 sheets, a plat view, an elevation showing 3 sides, and a foundation plan of the floor and footings. I had some very minor changes as I've built, not more than 2" difference from initial. I expect if I did something around 2ft change, they might care a lot more.

 

[rburke65]

Years ago dad had a 2 car garage and wanted it bigger, much like yours. We hand dug for the footer, laid block, poured concrete floor. Then we framed the 2 side walls. We cut out the existing rear wall from the bottom plate to the peak, braced it, and the slid the rear wall to the new location, tilted up the side walls and nailed. Dad was quit the guy. Miss him.

 

[Cyberbear]

I live in California and a simple 240 sq/ft addition is no big deal, at least where I live in Kern county. I've always acted as owner/ builder and avoided lots of problems by subbing out the work and getting estimates for the different phases of my job.
Add up all the estimated costs and divide by 240 to get a close estimation of your project by the square foot. Many general contractors use sub contractors, then add on a percentage as profit which you end up paying for.

 

[nadogail]

Years ago, I went to a local lumber yard, and they had a drawing and bill of materials for one and two car garages. The idea was you could take their drawing in to pull the permit and then build from the drawing.

Of course, they were ready to quote you a package price for the kit of materials for your new garage.