concrete question
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concrete question
I have a 4" concrete floor in my workshop and want to raise it another 4". Can I just pour another 4" on top? If so what prep is needed? I also would like to add tubing for radiant heat.
Postmaster
Joined: Aug 2004
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From: North of Boston MA
Is this a work shop floor only or is it in your garage? If it is just a workshop and not subject to major loads you could probably get away with pouring the new slab directly onto the old slab. If it were me I would probably use a concrete bonding agent to get the new concrete to stick to the old better. Before you do anything, remove any spalling concrete, blow all the dirt and dust off with the compressor and clean it all with a muriatic acid solution.
If the concrete will see any kind of heavy loading such as a vehicle, you should probably dowel the two slabs together and use reinforcement (wire mesh should do).
Radiant heat in a workshop sounds great by the way.
If the concrete will see any kind of heavy loading such as a vehicle, you should probably dowel the two slabs together and use reinforcement (wire mesh should do).
Radiant heat in a workshop sounds great by the way.
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Thanks for the advice, I'm raising the floor because it is below the drive grade and also the finishing of the floor was terrible. It has an uneven finish and dips in it. The shop is 30 x 50 and I don't want to rip the old floor out if I can avoid it. Oh yeh, the door is 14' high no problems there.
Last edited by billbain; Jul 15, 2005 at 08:52 AM.
Post Fiend
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From: Atlanta GA
Is there going to be any problems with the additional weight such as retaining walls or the floor itself sinking further down? That would be about 500 cubic feet (12 tons?) of additional weight?
Logistics Pro
Joined: Nov 2004
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From: Lancaster County PA
I am not a concrete technician (although I play one on TV).
What little experience I have and supplement with common sense says this:
Clean the surface of the old floor thoroughly with a high powered detergent suited for the task (TSP?) and let it dry. Coat it with a bonding agent made for skinning concrete onto concrete. Use reinforcing rod or mesh as per commonly accepted practices, and pour away.
If the original floor was laid upon the proper ballast, the additional weight should not cause it to settle, and the reinforcement will help to ensure that it does not.
At any rate, that is the way I would handle it were it my garage floor......
What little experience I have and supplement with common sense says this:
Clean the surface of the old floor thoroughly with a high powered detergent suited for the task (TSP?) and let it dry. Coat it with a bonding agent made for skinning concrete onto concrete. Use reinforcing rod or mesh as per commonly accepted practices, and pour away.
If the original floor was laid upon the proper ballast, the additional weight should not cause it to settle, and the reinforcement will help to ensure that it does not.
At any rate, that is the way I would handle it were it my garage floor......
Postmaster
Joined: Aug 2004
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From: North of Boston MA
Originally Posted by rebocardo
Is there going to be any problems with the additional weight such as retaining walls or the floor itself sinking further down? That would be about 500 cubic feet (12 tons?) of additional weight?
I assumed from your description that this is a slab on grade. If this isn't the case then you might just want to get an engineer to look at it.
Another thing you may want to do is have a level line marked out around the perimeter of the shop. Get a good laser level or surveyors level and mark a constant elevation line 4" above the highest point in the existing slab. (I am assuming that you want this level).
Good luck.
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The bonding agent over a properly prepared slab is the way to go. Generally, 2 inches and below require a special epoxy bonding agent. With 4 inches, you can use the "white milk" (latex), or even a slurry coat mixed with portland, Flex-con (by Euclid Chemical or equal), and water. You may want to consider fiber mesh too. Less hassle and approved as a substitute for wire mesh (6x6 10/10). Be sure to allow for expansion with plenty of control (sawcut) joints!
Finally, any nasty cracks may eventually show through your new slab.
Be sure to cure & seal it to minimize cracking and slow down oil penetration.
Please post any questions,
Finally, any nasty cracks may eventually show through your new slab.
Be sure to cure & seal it to minimize cracking and slow down oil penetration.
Please post any questions,
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Fiber reinforcment is great, but if you are doing radiant, you'll need the wire mesh to anchor it anyway. Also, the fibers stick up at the surface and make sweeping the floor more difficult. You won't see the fibers until the floor is wet or you push a broom over it and they grip onto every bit of dirt. I had my 1500sf shop done last winter, radiant, wire mesh, fiber, and sealer. I suppose the fibers will wear off eventually.
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Good point about the wire mesh/fiber. Just throwing that out there, for convenience sake and all ( + steel prices). A lot of concrete guys have switched to fiber over the last couple of years because of steel pricing, and may just use it anyway unless asked otherwise.
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Originally Posted by jesta302
Good point about the wire mesh/fiber. Just throwing that out there, for convenience sake and all ( + steel prices). A lot of concrete guys have switched to fiber over the last couple of years because of steel pricing, and may just use it anyway unless asked otherwise.
Alot have switched to plastic reinforcement, or the new, webbed mesh(looks kinda like snow fence, comes on a roll, but closer to 1/8 thick.)
Around here the ready-mix plants don't like dealing with the Fiber-crete products, and charge quite a bit more for them compared to regular mixes.
Whatever bonder you get, make sure it isn't re-emusifiable. There are tons of them out there, and the last thing you want is any break down if you get water intrusion between the slabs.
Junior User
Joined: Jun 2005
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hi Billbain..you lucky guy! radiant heat! no open flames to ignite dust or cleaning fumes! Fall asleep on a warm floor..done that..What does your heating guy say about putting down a foam barrier between the layers ..That directs the heat up instead of down...Even a new goverment building with regular gas heat ; I helped install the floor; we put down a two foot strip of blue foam at the edges,,,I remember that most heat loss is the perimeter edge...Its the best heat, the mice will thank you every year..good luck
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Joined: Mar 2005
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From: Southern New England
I don't see a problem adding 4" to your floor as long as the foundation walls are high enough inside to contain the new concrete.
A couple of things worth mentioning though... The garage door tracks will need to be raised. The entry door will have to removed, the header raised and then re-installed. Wire mesh will need to be used if you're using radiant heat so you have something to tie the tubing to. Pouring a floor with radiant heat is a MAJOR pain in the ***, you will have your work cut out for you. The insulation and vapor barrier does not let the water out of the concrete and it takes forever to set up. Best to pump the concrete because moving 19 yards of concrete over the tubing and mesh takes great care and patience.
A couple of things worth mentioning though... The garage door tracks will need to be raised. The entry door will have to removed, the header raised and then re-installed. Wire mesh will need to be used if you're using radiant heat so you have something to tie the tubing to. Pouring a floor with radiant heat is a MAJOR pain in the ***, you will have your work cut out for you. The insulation and vapor barrier does not let the water out of the concrete and it takes forever to set up. Best to pump the concrete because moving 19 yards of concrete over the tubing and mesh takes great care and patience.
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Thanks for all your replies, great advice! I already have a plan to cut the tracks and bottom of the door, the bottom seal is damaged anyway so it's a good time to replace it. I have some experience with the tubing, having installed it in my basement, addition, and attached garage. The walk door is already about 6'' above grade, I don't know why it was built this way but it works in my favor. Thanks again.
Posting Guru
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From: Northern California
I had the foundation in my shop done with the radiant heat tubing installed in it. They used wire mesh and the fiber. The fiber is "fuzzy" for awhile, but it will wear off the surface and you wont kow the difference after its been used for awhile.