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Thread: Garage Shop Floor Renovation Question

  1. #1

    Garage Shop Floor Renovation Question

    Hi all,

    I plan on installing my shop in the three car garage attached to my home.

    In addition to having the usual woodworking tools, I also have some heavy iron machinist tools (Bridgeport, Reid surface grinder, and a massive old South Bend 16" lathe).

    Given the machine tools, I had planned on keeping the floor as concrete and using anti-fatigue mats at each machine as needed.

    The house and garage were built in 1926 and the floor in each bay of the garage pitches to a central drain (three drains total). The shape of each bay's floor is an inverted pyramid with a rectangular perimeter and a depth of about 3".

    While it is certainly possible to shim the various machines level, the LOML insists on being able to park her car in the bay closest to the house, hence some machines will need to be on movable bases. Moving even something as light as a table saw (light when compared to the Bridgeport, anyway) gets to be a real pain when needing to go over the "hump" between bays.

    I've been investigating the possibility of pouring a skim coat of concrete to fill the depression in each bay, but am concerned that the edges -where the concrete would essentially feather to virtually 0" thickness - will make for a weak link leading to eventual deterioration of the entire floor.

    One contractor I spoke with suggested breaking the floor up and repouring everything to be level. I don't know if any of you have ever tried to work with 80 year old concrete - it is harder than the proverbial rock and is extremely difficult to break with even a jackhammer. This would also be mega-expensive and time consuming.

    Anyone out there have any suggestions on how to create a level and durable floor that would hold up to both a heavy car as well as movable woodworking equipment? The machine tools will be shimmed level and bolted to the floor permanently.

    Thanx,

    Brian

  2. #2
    can you frame up the shop area and use plywood?

    re-reading your post doesnt sound practical. but its better than tearing the floor up. and yes you will have issues with cracking at the shallow ends.

    I feathered out some when I closed an old porch once, and i feathered out to 3/4 then used self leveling concrete the rest of the way. It was under carpet, and eventually the bond gave out ....

  3. #3
    Join Date
    Oct 2006
    Location
    Mazon, Il
    Posts
    375
    Break it out and essentially start over. The pitch can run toward the doors and the floor will be Flat. You are not going to loose $$$ by doing this in terms of value added to the house/garage. Be done with it, and do it right.

    You also may be able to float 2" or more inches of new concrete over the existing floor, provided it is prepped right, but you may not want to sacrifice the drop in overall height.

    But if you want it right, start over and have it repoured.

  4. #4
    Join Date
    Sep 2007
    Location
    Bucks County, Pennsylvania
    Posts
    940
    I have been up this road before.

    I had a garage that the floor and footing was poured in a mono-slab - then the walls were placed on top of this slab. I had differing opinions regarding the safety of cutting back the slap floor a foot or so from the wall then breaking up the main area and pouring a new floor.

    So we went with a leveling pour over the old without taking out any of the old floor. We used a modified concrete product that had little lenths of -- I think they were fiberglass - strands. We also had to coat the old floor at the far end of the garage with a binding agent - this was the thinnest part of the pour since the garage sloped toward the door and I wanted it flat. The floor was still an inch thick at the thinnest area. The floor worked out quite well but because of the products used and the extra time in finishing needed -- the floor was more money than if it had been a normal four inch concrete pour. This was also in a heated garage - so I do not know how it would stand up to the cold.

    If you have a stand alone floor that can just be broken up - that is what I would do. Any concrete contractor can do this and you end up with a nice new flat floor. I also have seen a lot of old floors taken out -- unless your floor is very thick (over 8") a pneumatic jack will make short work of the floor. They use them to remove roads and bridge decks!

  5. #5
    Thanks for everyone's comments.

    Unfortunately, the garage walls are built on top of the perimeter of the slab, so jack hammering out to the inside of the walls is not really an option - hence the thought of skim coating the entire floor.

    I had thought of possibly affixing (epoxy and lag screws) a strip of 1/2" thick aluminum or stainless steel around the perimeter of the each of the bays - including just behind the garage doors. This would give a 1/2" minimum thickness to the edges of the top coating and also help prevent that edge from fracturing. Any thoughts about that idea.

    Brian

  6. #6
    Brian, the walls arent a deal breaker.

    Usually the demo process would be to sawcut the perimeter and then the slab into smaller chunks before removal. You could saw cut just inside the perimeter of the walls and when you repour, the only thin pieces woud be real close to the wall perimeter.

    The angles you spoke of wont help alot ... its the bond between the new and old that would fail, and for concrete to be structurally supporting anything it needs a minimum of 2" thickness. Foot traffic you may get away with it, but vehicles and concentrated loads of casters are a different story.

  7. #7
    Join Date
    Aug 2007
    Location
    Laporte County, Indiana
    Posts
    240
    Brian,
    I have to agree that a new floor maybe in order. Even as you state that the walls are construsted on top of the exisiting slab, a concrete contractor should be able to give you an estimate of replacement. And a recommendation as to cutting the floor back an putting in the new floor. In our area the concrete guys like this kinda of work as it does not involve any form work.
    Good Luck
    Remember a bad day in the shop is much better than a good day at the office!

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  8. #8
    Join Date
    Mar 2003
    Location
    SE PA - Central Bucks County
    Posts
    65,693
    I'll pile on...new floor is the best way in the long run.
    --

    The most expensive tool is the one you buy "cheaply" and often...

  9. #9

    Check this out

    Go to elitecrete.com besides the great decorative concrete system they have, they also havesome great products for leveling and patching concrete. They will only sell to trained installers, I took the 2 day training seminar so I could do some of the decoritive work around my house. Just another one of those projects I havn't got around to yet. I did do a couple projects for others though. The stuff will adhere to the concrete if you prep it right.

  10. #10
    Thank you again for all your comments.

    Talking with several local contractors, as well as from your comments, I guess I'm going to have to bite the bullet and remove/replace the floor.

    Of course, this could also be the perfect excuse to just build a free-standing workshop! That's an even better idea.

    Thanx again,

    Brian

  11. #11
    Join Date
    Apr 2005
    Location
    Splendora, TX
    Posts
    703
    Quote Originally Posted by Brian Backner View Post
    ...........Of course, this could also be the perfect excuse to just build a free-standing workshop! That's an even better idea.

    Thanx again,

    Brian
    Now your talking!!!!!!!

    As an earlier poster had previously stated, short of removal of the existing slab if you could afford losing the height, instead of a leveling pour feathering to the edges, you could pour added thickness to your existing slab, I would make the thinnest section a minimum of 2".

    Still like the free-standing shop idea best myself though !!
    David

  12. #12
    One idea may be to remove the high spots and pour over the whole thing.

    Ardex is a manufacturer that makes a product that will pour to a feather finish and stand up to traffic, but you would need to section it off so that you poured up to say a 1 1/2" thickness and then go with the feather finish material. There are certainly products that will do what you want to do but you have to ask at what cost to preserve what you have there now.

    James Davis

  13. #13
    Pouring a new floor over old one will work only if new floor grade is equal to or preferable, lower than wall sills. You mentioned walls are built over the slab instead of on footers. If you pour over the top of it and the new floor is higher than the sills, you are asking for sill rot down the road. Water will certainly find a way down to sill. My barn is built the same way.
    I saw on last seasons this old house (Newton, MA), they had to tear out a large portion of the sill and even wall studs because of the same situation.
    My advise is roll up your sleeves do a perimeter cut and jack hammer it out. A back how may be able to reach inside far enough to do most of it.
    Good luck!

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