New garage floor questions..where the 911 lives

[RickM]

Inspired by the Garage floor paint question, I am planning the demolition and repour of my garage floor for this spring. Presently, my floor has a crack, pretty much in the center, and one side is about 2" lower than the other. What a pain and dangerous when jacking up the 911!

In any case I'd like to maximize my return when executing this repair. My questions are:

-Has anyone incorporated drainaige into their floor?
-Recommendations on plane or system to assist in good drainage. (To accomodate melting snow on car, rain, etc)
-Should I use a vapor barrier above a gravel base ? What type of barrier?
-Any type of mix or additives I should have utilized here in the Northeast?
-How long to cure before top coating or polishing?

Also, has anyone installed the iron type drainage grates in the apron of their driveway/garage floor? If so, where can I get these?

Rick

[JoeF]

Rick,
I live up 287 a way, We just finished our garage addition in Nov.
It is an addition, so half the floor is original, half the floor is new.
Our mason did not put in a vapor barrier. He did make sure to put down renforceing wire and use cement delivered with some kind of fiber in it to prevent cracking. It cracked anyway. You may have better luck being that you are replacing a floor on ground that has been packed down a while.
As far as incorporating a drain into the floor, it may be frowned upon due to environmental concerns, you may want to check with your local building inspector.
Also,I am pretty sure you are required to pitch the floor at a specific rate starting high on the back wall, pitching downwards towards the garage door. This is a ventilation consideration more than a drainage consideration.
There are two kinds of sealers, one for new cement, one for old floors. The sealer for new cement can be use with in a few days of hardening.
I did not apply any kind of epoxy coating because it was starting to get cold out and I found out it would take a long time to dry in cold weather. But I would have preferred to do it before I put cars in the garage.
Due to drainage problems, our paving guy installed HD iron grated / cement drain boxes. They are 8' long, and about 2' wide and 2' deep. I will call him and see where he got them.
JoeF

[Hetmann]

About 3 years ago I built a 20'x22' shop. We put down a vapor barrier before pouring the floor. We added a terra-cotta color to the concrete. Once the floor set, I had the concrete guy cut it up into 2'x2' squares. I painted the floor with a polyurethane finish. The floor looks like tile and has held up to various adhesives/sovents/paints quite well. All cracking (so far) has been in one of the cut joints.

[RickM]

Joe,
Thanks for the info. Is the sealer for the new floor clear and durable?
Rick

BTW: Where up 287 are you?

[JoeF]

Rick,
I wasnt really that impressed with the sealer, but I wanted to protect the floor with something before I put cars on it. I am sure I am going to have to do a real good cleaning or acid wash before I coat the floor with an epoxy coating.
I am off Rte. 23 in Kinnelon.
JoeF

[Rob McKibbon]

Hettman has a great idea; we do that alot with Terra Cotta coloring added to concrete and sawcut in 2'X2' sections; about 1/4" deep sawcut. You can fill the sawcuts with black grout too for a very nice effect. The color is right in the concrete so it wears, chips and looks good forever.

Rick,
Your slab has cracked because the home builder did not compact the soil properly under the slab before installing the concrete. You can add drains, depending on the elevation (height) of your slab and where are you going to drain to. I would install an in-slab catch basin about 2'X2' at the lowest point of your drain system. This comes with a metal lid and works as a sump/ separator and tie-in for your out going drain (to storm/sewer). You can run your drain trough down the center of the garage front to back or just inside the garage door, depending again on your drain connections.

Use string lines to establish your elevations and slopes. Make sure you have a minimum of 4" between where the top of your slab is going to be and the soil. Don't crown the soil, which weakens the concrete. I would place all the soil & gravel to the level you want, then use a spade shovel to dig out your trenches and catch basin. The trenches install by pounding pieces of rebar into the ground that will suspend the trech drain and allow concrete to flow under it and around its sides. The drain suppliers will provide good details with their product, easy to follow:

There is a Great product we use manufactured by Zurn
Zurn Industries Inc.
Flo-Thru Operation
2855 Girts Road
Jamestown, NY, USA, 14701
Ph 716/665-1132
Fx 716/665-1135 (call, they should have website?)

Zurn makes premanufactured troughs from 6" wide to 24" wide in various lengths and depths. The nicest thing about their product is it comes with a presloped bottom when you order it, it's modular and lightweight. The system comes complete with everything you need to install, including the top cast iron grate.

I've got the Canadian Distributors too, if anyone needs?

Jackhammer and remove your slab. Remove up to 2' of soil and compact the base very good. You can reinstall the old soil if it is free of debris/ roots and contains no topsoil. Material should be clean and compactible. Use a 6" Gravel (road crush) base under the slab and compact it too. You can get compaction tests done very inexpensive from a geotechnical engineer firm (soils engineer), I would. They calculate moisture, density and compaction, the soil can be deceiving?

Once the gravel is installed you can install your vapour barrier, we use a 6 mil poly, but your lumber supplier will tell you what to use. If the gravel has sharp edges or is unsmooth in general, allow for a 2" sand topping to place the barrier on. The sand requires to be vibrated with a vibrating compaction tool. Overlap the barrier joints by 6". Install a 10mm (1/4") reinforcing steel (rebar) mat on 2 ft. centers. Lay the rebar 2 ft apart front to back and then 2 ft. apart side to side. You will now have a grid of rebar laying on your poly vapour barrier. At each place where the bars cross use tie wire to tie the bars together, and then place a 2" chair under the rebar. You want the rebar to be in the bottom part of your slab, but not on the ground. Make a tool from some left over rebar that can hook the rebar, for when you pour the slab. Immediately after pouring the concrete onto the mat, if the mat falls to the bottom; you hook it and snug it up into the concrete, trying to keep it off the ground and in the bottom half of the slab thickness. The rebar will help to strenghten the concrete, but most important it allows the concrete to expand and contract without cracking - properly placed rebar will assist in avoiding cracking problems.

Once the rebar is installed, chaired (lifted), use a mastic poly tape to patch any holes in your barrier caused by installing the rebar and traffic over the poly. Check your slab heights again with your string line and tape measure. Run the string from side to side and measure down to the poly. You should have 4" minimum for concrete thickness. Now phone me and I'll come inspect it - just kidding? You're ready to order your concrete.

When the concrete arrives, be sure it was batched less than 1 hour before - some residential guys batch a large batch and go from small job to small job offloading the concrete. Do not accept concrete that is old - problems will occur. The next is the consistency of the concrete - you want what is called a 3" slump; when you place the concrete a certain way in a cone, then lift the cone, the concrete slumps by 3". So in other words you do not want a runny, watery concrete mix. Water is the biggest culprit for shrinkage cracks! With a good concrete mix - Let's see, 25MPa strength, Type 10 Cement, 4-6% air entrainment, 3" slump should be enough info for ordering your concrete.

Place the concrete into the slab area, screed it off to the height, slope required, let set for a few minutes, then bull float it, let set until you can walk on it, then finish float it. Finishers will know what to do, look for a Portugese man named Tony? He will definately know what to do. Hah. Very popular and I recommend highly, is shaking on a concrete hardner when bullfloating, finishing your slab. You can get many colors of hardner, they come in powder like form and you shake on a healthy 1/16" amount and work it into the top of your slab. French Grey is the most popular color.

About 24 hours after, place sawcuts about 1/4" thick into the top surface of the slab at about 6 foot centers each way. This will allow the concrete to crack where you want it to crack and not wildly. Concrete does crack, and this is very normal. I have done slabs that don't crack at all, but they are tough to do and expensive. Keep in mind that the concrete will always crack at the weakest point. If you do put in a drain trough, this will also act as a control joint and cracking will occur at each end of the trough, so put a sawcut there to control the crack. After a week, the sawcuts can be filled with an epoxy caulking if desired.

At about 24 to 72 hours you can spray on a concrete sealer. Equipment rental shops rent out spray cans for the stuff and probably retail the sealers too?

You'll have a great slab for the next 25 years.
Have you thought of heated slab; now those are cool.

Edit: the sealer is clear, will provide some kind of gloss and will help to keep the dust down.

[sammyg2]

Rob, can you give us any details on how to do this?

Let me guess, you make a living in construction?
This is one of those threads that I'm going to print out and stash away for future reference.

[RickM]

Ditto to what Sam said. This thread goes into my project folder! Thanks for the great info.

BTW, I have access to storm drainage right outside the garage, so this should help with planning. Also, I didn't consider the saw cuts but it cetainly sounds interesting.

[Jeff]

Rick, Don't know what your budget is so I'll just throw this out. If your budget allows you may want to consider putting radient floor heating in your garage. Before you pour the cement you put a series of tubes that have hot water run through them and in turn heats the garage. I wish I had something like that when I lived in the cold. Just think, warm floors when you are working on the Porsche.

[JoeF]

Rick,
Those precast cement drains with the iron grates can be found at Peerless Concrete Supply, Butler, NJ 973 838 3060.
JoeF

[cegerer]

Good information Rob! One thing I would add, is to make sure that isolation joints are placed between the foundation and slab. These typically consist of roofing felt to prevent the slab from bonding to the foundation wall. It allows the slab to move freely as it dries and shrinks and reduces (guess what?) drying shrinkage cracks! My company investigates 1000's of structural failures and cracked slabs are close to the top of the hit list. -- Curt

[david c.]

Hey, I'm sure you've already thought of this and decided against it, but I was really impressed by the idea of hot water heating up the garage floor in Cary's thread from last fall. When I build my garage I will absolutely be doing this. Just a thought.

[rfuerst911sc]

Any chance of putting in a mechanics pit?This is not too hard to do and makes under car service much easier,just a thought.

[Rob McKibbon]

Heating can be done with "electric" mats now too? If you don't have gas or boiler system and you do have power - you could look into. Very simple system that works.

We use them in bathrooms under tile floors.

[ChrisBennet]

Originally posted by rfuerst911sc
Any chance of putting in a mechanics pit?This is not too hard to do and makes under car service much easier,just a thought.

Pits aren't used anymore for insurance reasons (they collect gas fumes) but even if they weren't, I wouldn't want one. What can you do on a 911 with a pit? Change the oil and adjust the ride height? You can't get a jack under there to remove the engine or change tires and you can't roll anything over the grate in the floor that covers the pit when you aren't using it. The neighbor has one I can use any time and I've only used it once in 10yrs.
Now if they'd let you..a garage floor that had a bay that was level would be great for setting cornerweights.
-Chris

[jmohn]

While I agree with most everything Rob McKibbon said (nice description, Rob), there are a couple things I would do slightly different if I were re-doing my own garage floor. Keep in mind garage floors in climates subject to freeze/thaw cycles (i.e. where I live) are very difficult to keep "pristine". I'd remove any soil that is organic or expansive (fatty clays, etc.) if you don't know get a soils engineer to advise, replace with non-expansive, well draining soil (very coarse sand, gravel, etc.), I'd use "number 4" bars (i.e. 1/2" diameter), minimum "4000 pound" mix (this may equate to "25MPa strength"), 5" thick slab, 3" slump is excellent but there are "admixtures" than can make 3" slump mix act like 5" slump (much easier to place and work) ask at your mix plant, consider adding steel fiber mesh (again ask at the plant, it aids in resisting cracking, but can be more difficult to finish and may cause a "texture" in the surface). In-floor hydronic heating is great, but at a price, we've seen a couple commercial floors with it and quite a few interior residential floors but no residential garage floors. If you choose to try in floor heat be certain it's installed EXACTLY as the manufacturer requires (otherwise you've wasted your money).

BTW, I'm jealous, my floor is cracked, and it's going to stay that way. There's saying "in the business" -- "there's only two kinds of concrete, the kind that's cracked and the kind that's gonna crack".

Good luck,

Jerry M
'78 SC

[diverdan]

Buddy of mine built his dream shop in Michigan and used 2 or 4 inches of foam under the concrete
. The floor never feels cold to the touch.,
Diverdan

[RickM]

This is all fantastic info. I think I ruled out the heated floor as it doesn't seem practical for me. If I were to heat the area I think I'd use one of those fat old garage hot air heaters (Natural gas) that mounts up on the wall.

The pit idea got me thinking....but I think I'd rather go with a lift. I'd like to park one car under the other for storage and also use it to work on the wheels and related components. That leaves a two arm lift...but I'm not sure how stable that is.

Regarding the cuts in the floor: This seems very appealing but as I roll a jack over a cracked area it is plain annoying. Would it be the same going over the cuts? Possible remedies mentioned by the group: Epoxy filler, caulk or grout.

Please chime in with thoughts.

Rick

[Rob McKibbon]

Hi Rick
I've built liquor stores in Alberta (they drink alot there, bunch of rednecks), and their tolerances for flat, level floors are unbelievable! They roll pallet jacks over the floor all day long, and breakage is a big loss for them. We use a very low slump concrete (1") and then add a super plasticizer just before placement, lazers and the finest finishers money can buy. Our floors were rated the highest in Quality upon completion, and our first warehouse became the flagship for the Province, back in 1988. We can do FLAT.
As stated, use a two part epoxy caulking. Blow the sawcuts out with compressed air, overfill the joint and then when dry, shave it off level with your slab. It won't be perfect, but close. A whole lot better than having an annoying crack where you don't want it. "Control" joints is what they're called. You control where the cracks gonna be, and you will get them 100% guaranteed.
Glad to help, as I'm not a mechanic and really enjoy all the help I get from the Pheads on THIS bbs.

[stealthn]

Originally posted by Rob McKibbon
(they drink alot there, bunch of rednecks

HEY!!! That's it.............NO SOUP FOR YOU!