Garage slab estimate

[70datsun]

Hi everyone,

I'm getting close to starting my addition off the back of our house. I got a quote from a contractor who was recommended by my general contractor for doing quality cement work. The quote he gave seems a little high to me but I wanted to get some opinions here.

Here's the dimensions and specs:
680 sq. ft. 4", 3000 psi mono-slab with welded
wire mesh. 12"x24" perimeter footing with 3
horizontal #4 continuous rebar and #4 dowels at 4" O.C

Cost=$5829, which is around $8.50/sq. ft.

Any thoughts?

 

[rzims]

I just quoted a 7500sf slab here in California - 8" thick over compacted baserock with rebar at 14.50/sf if that's any help at all.
Included excavation/offhaul of native soil as well.

 

[AVIVIII]

I just poured a 5" floor inside existing frost walls. Compacting, vapor barrier, mesh, and concrete came to ~$4.55/sqft. It took About 21 yds.

It's sounds like you're doing a monolithic slab, so a disproportionate amount of concrete is going to be around the edges. It sounds pretty reasonable to me, especially with all of the steel work in there.

Sent from my SM-G930V using Tapatalk

 

[lakeroadster]

It's sounds like you're doing a monolithic slab, so a disproportionate amount of concrete is going to be around the edges. It sounds pretty reasonable to me, especially with all of the steel work in there.

Agreed..

Running some quick rough numbers.. there's about:
227 cu-ft of concrete in the slab
208 cu-ft of concrete in the perimeter footing

Converting back to the 4" thickness... you end up with a little over 1300 sq-ft, not 680 sq-ft

Looking at that sq-ft you're at $4.47 sq-ft.... reasonable, as AVIVIII points out.

Not really an apples to apples comparison, but you get the idea. A lot of concrete in those footers.

Does the price above include compaction of the sub-grade materials?

 

[finn]

We're doing a 4" slab inside the 16'x60' pole lean-to on my shop. The quote works out to about $4.45/sq ft.

 

[70datsun]

Thanks for the replies. Certainly calculating price per sq. ft. with the depth brings the price more in line with prices I had seen. It seems in the estimate that compaction of base material is not included. But most importantly, I just wanted to be sure that this quote seemed within the ballpark. I don't plan to search around trying to nickle and dime it. The guy came highly recommended and I was happy with him after the site inspection.

I'll be starting a thread on the whole build pretty soon, so I'll try to keep you all in the loop, just for fun.

Cheers!

 

[Falcon67]

Last I checked here next door in Tx it's running $8~12 sq/ft for flat work, depending on particulars. How is your soil there - I added grade beams because we have expansive clay, bet not so much around Albuquerque.

 

[wssix99]

Here's the dimensions and specs:
680 sq. ft. 4", 3000 psi mono-slab with welded
wire mesh. 12"x24" perimeter footing with 3
horizontal #4 continuous rebar and #4 dowels at 4" O.C

For a project your size, none of this matters as the materials are a small part of the overall cost. The things that are getting you are machines and labor.

Cost=$5829, which is around $8.50/sq. ft.

Small jobs shoot up in cost per square foot because the costs to transport machines and use machines and operators for a full day (even when you only use them for part of the day) are the same regardless of the size of the job.

You can probably find a contractor that will estimate your job off of the material and size of the pad (they are out there!!!), but those are the companies that will do shotty work and leave you hanging. ... There are probably good reasons your general contractor recommended this company.

I had this problem when doing some flat work on my house. (We had to do our flat work in phases and some were small jobs.) I was able to get the cost way down by doing a few things:
- Allowing my contractor to do my job on a Saturday morning, (when they typically work a half-day) and at their convenience. I lost my ability to pick when the work happened, but they committed to showing up in a certain month to get it done. (This enabled my contractor to avoid having to charge me for a full day of work for the workers and machinery operators, when they only had a half day of work.)
- Allowing my contractor to drop off machines he was going to use on my job and store them on my property during the week as he passed by. (This allowed him to be more efficient and skip a trip to his machinery yard the day of my job to get the equipment.)
- Accept tooled joints over saw cut joints or do the saw cut joints myself (this avoids an extra partial-day trip)


You might also be able to get creative with your contractor and understand what the sources of his cost are to get the price down. For example, you may be able to go to a local equipment rental and rent the machinery he needs for less money than it would cost him to truck, unload, and operate his own equipment. (He'll use his operators to do this, who are up to 4X as expensive as the one person who will do the delivery for the rental company.) Etc.

 

[brownbagg]

Hi everyone,

I'm getting close to starting my addition off the back of our house. I got a quote from a contractor who was recommended by my general contractor for doing quality cement work. The quote he gave seems a little high to me but I wanted to get some opinions here.

Here's the dimensions and specs:
680 sq. ft. 4", 3000 psi mono-slab with welded
wire mesh. 12"x24" perimeter footing with 3
horizontal #4 continuous rebar and #4 dowels at 4" O.C

Cost=$5829, which is around $8.50/sq. ft.

Any thoughts?

you dont get size of bldg for calculation but roughly it could be done as low as $2000 inncluding materials

does that include excavation, compaction, setting forms, digging footers, that all stuff you can do, huh no, then prepare to pay out the .......

i can get concrete finished around here for materials plus $500 on average shop slabs.