workshop floor rehab

[Tom Godley]

I need to replace the concrete floor in the older of two buildings that make up my shop/studio - it was originally built as a 25 x 35 garage. This is a rough poured single slab with a crown in the middle and a slope of about 5 inches toward what was the doors and is now the newer second building.

I have been putting this off for a couple of years. The ultimate would be to have a heated wood floor - but I see no way to put a floor over over the current uneven concrete one. I recently got some estimates to remove all the old slab and install - stone/ vapor barrier / rigid insulation and then a 4" finished slab with pex pipe for a future heated floor - 15k

I did not price out having a proper floor structure installed over the whole thing -- then I would need a foundation in the middle for the 25" span. I would in effect be making a closed craw space between the rafters and the old floor.

Am I missing something -- anybody do this?

[Greg Woloshyn]

I'll be doing this exact project once the weather breaks. My shop is smaller than yours at 20 by 19 and I got a few estimates to tear out the floor and re-pour for around $2500. After talking to a bunch of people I decided I'm gonna take on the job myself, with the help of some friends who have done masonry work in the past.

If you have footings installed and the actual garage isn't sinking it shouldn't be a terribly tough job. I'll be renting a jackhammer and a dumpster for the demolition, then having the concrete delivered after I run my re-bar grid and make my moldings for the floor. For my 20 by 19 floor with a 4" slab, I'll be paying around $600 for concrete, which isn't bad at all. That 15k figure you got was mostly for the labor involved in ripping out the old slab, which is cake for the contractors who have all the equipment to get it done fast. Save a ton of money and do it yourself, it'll be some work but it's definatly worth the money saved.

[Logan William]

I would agree that it would be worth it to price out renting the eqiupment to tear it out and do the majority of the work yourself. Concrete in my area delivered is about $105/ton for 3500 PSI, everything else your paying for is labor and tools. The demo isn't that hard, just takes some hard work. I would also consider pricing it as you tear out and prep and a crew comes in and pours/finishes. The finishing work is where the experience can really pay off, the last 8" thick slab we poured back home was 24' x 40' and we did all site prep/foundation/footings and then stood back when it was time to pour the slab. They charged 800 I think for that and it was easily worth it, but we had also worked with them several times before on other buildings on the farm so we knew what we were getting.

[phil harold]

How about just using sleepers over the old floor?

or
If you have the cieling hieght
you can level out the floor with gravel then add 2" foam and concrete on top

[Foras Noir]

I would lend you my machines and even help out with the labor. I am West coast so it does you no good.

I am saying this because I bet wood people in your area are no different. I lend out my heavy machines to woodworkers all the time. I bet your locals will help you.

Do you have a local guild?

[Jim Andrew]

You didn't say if you have overhead doors on your shop, but when I bought my skidsteer, the salesman said the concrete guys are using them with forks to remove concrete slabs, said it works better than anything. Haven't tried it yet, planning to replace my approach slab to garage, just haven't got that far yet. He said you can pull it up in pretty good sized chunks.

[Tom Godley]

The concrete is not something I am going to do myself.

My shop is heated but the floors are cold. The newer section does not have a heated floor but it does have insulation under the slab so it is not as bad. I turn the heat up when I am in the shop -- but the floor never really gets that warm. I am finding that the hard floor and the cold have an effect on me that they did not have -- when I was younger.

I was not expecting the 15k cost for the pex/slab.

If the old floor was level enough. I would have put down a vapor barrier and two stacked 2x lumber on its side. I then could have installed 2" rigid foam between the pressure treated sleepers and then pex pipe on-top of the foam all covered with floor sheathing and then if I felt wealthy -- a finished floor.

The lowest point of the old floor is where it meets up with the floor of the newer building - it then slopes up to a high point of 5" at the far wall. So to level the old floor with a minimum of 3" of concrete at the thinest point it becomes 8" thick where the two floors line up + then the new wood floor structure of approx. 4.5. So I end up with a 12.5 step ??

[Mark Boyette]

You didn't say if you have overhead doors on your shop, but when I bought my skidsteer, the salesman said the concrete guys are using them with forks to remove concrete slabs, said it works better than anything. Haven't tried it yet, planning to replace my approach slab to garage, just haven't got that far yet. He said you can pull it up in pretty good sized chunks.

absolutely Jim. I've removed a few slabs that way. Cut the slab in 4 x 4 sections with a walk behind saw. The forks make it easy to pick up and put in truck. Literally only takes minutes once cut. There are places that take the old concrete for free. We have a place here that takes it, grinds it up, and then sells it back to you for base (304).
Mark.

[Mark Bolton]

The concrete is not something I am going to do myself.

Concrete is not something ANYONE who doesnt work with it on a daily basis can be "good" at doing.

Anyone thinking of pouring their own finished slab as opposed to getting a professional finishing crew would have to have their heads checked. If you are pouring a sidewalk or barn floor, maybe, but when most finishers are charging about 1.00/sq' to place and finish concrete its pretty hard to scoff at 400-500 bucks for a perfectly placed and finished slab.

Doing the demo and setup is something to consider. With regards to some of the other replies, there is absolutely no need for rebar in a simple slab. 6x6 mesh is more than fine, and depending on your climate many may say it isnt even needed though we never run slabs without mesh.

The 15k could well be reasonable as none of us can actually see the job. If the contractor quoted a good base, 100% compacted base, metal, form work, place and finish, and perhaps sub contracted the radiant to a heating contractor. That price could easily be in line.

That said, you could likely easily gather up some help and with a bit of rental and some sweat do the demo and base. I would however leave the form work, place, and finish, to a good crew. Get references, go look at several jobs, and sub out the concrete.

I wouldnt skimp on the radiant either. If you dont find someone to help you design the layout you can easily wind up with a system that under performs. You can buy your material online from a place like Radiantec or other sources that will do the design but you will likely pay more for materials and also have to pay shipping as opposed to buying local. I would doubt any local supply house will do a heat loss and design layout for a homeowner.

Mark

[Mark Bolton]

Just for kicks, I re-read your post and for reference here would be some costs for materials only:

2" extruded ISO insulation under the slab - 1100.00 (based on 40.00/sht)
4" #57 stone base (16 tons) - 600.00
11 yds. concrete - 1250.00
6x6 Mesh - 250.00
Radiant Rough-in - 800.00 (installed)
Equipment rental (skid steer, jumping jack, plate compactor, bull float, power trowel) 1200.00

Rough tally about 5200.00, no form work, no disposal, ......

Works out about right. Triple the materials and equipment and you get your completed cost.

Mark

[Steve Kohn]

Trying to think a little out of the box....have you considered calling in a "mud-jacker" and having the floor leveled?

[Craig Summers]

Did you compete the work with 3 or more bids? Sometimes one bid just throws extra $ because they can.

I would figure out what the contractor would charge for each section of the work, you might find that one would rather do more demo vs the concrete.

If this is the entire project, you could take a look at Craigslist services section for the demo and gravel prep, this sounds like it could be a couple weekend jobs for beer money if you front the material costs. And then contract the pex & pour/finish

[Phil Thien]

What Craig says. Sub the demo work, do the insulation/forms/pex yourself, hire a crew to pour/finish.

[Jim Becker]

Tom, I could give you the number of the mason who did the work here at the house...he could help you get a level surface by pouring lightweight 'crete. Then you could float a thin wood sleeper and foamboard insulation plus plywood floor surface over that. It would be easy to do and would not require you ripping out the existing concrete to accomplish things. Dan is a pleasure to work with and a leveling job like that would likely not be terribly expensive or take a lot of time.

[Ed Harrow]

... Then you could float a thin wood sleeper and foamboard insulation plus plywood floor surface over that. It would be easy to do ...

And a huge improvement over a cold, hard concrete floor!