How to Waterproof Concrete Garage Floor?

[Gearhead Jim]

Hello, New Guy here.

Our house in the suburbs of Chicago is 37 years old. The floor in the 3 car garage is prestressed concrete slabs with about a 2" poured concrete topping, there is an unfinished storage "room" under the garage that we enter through the basement.

There is plenty of chipping and spalling in the topping, and a few very narrow cracks that allow water to seep through and drip into the room below. I want to stop the leakage, so we can keep the room clean and also to reduce deterioration of the prestressed slabs.

We can repair the topping and try to make the concrete waterproof with some kind of epoxy/polyaspartic coating (professional job), but I suspect the cracks will reappear from the expansion/contraction of temperature cahnges, and slight flexing as the cars drive in and out.

We can repair the concrete and then cover it with waterproof tiles or something similar, but I can't find any stories of how that has turned out for people. I don't want a showcase floor, but the rubber mats look too ugly for me.

Suggestions?
Thanks!

 

[ConCretin]

There are other things you can try but the proper product is called traffic bearing waterproofing. It is applied in a manner similar to an epoxy floor including all the required prep. As the name implies, it is designed to waterproof the substrate and is durable and flexible enough to stand up to vehicle traffic and flex.

You can buy it at HD Supply or other construction products companies.

 

[strutaeng]

Yes, traffic coating will work for this. It is not inexpensive.

Do you have slope down to the garage door? Water should not pond. Also, the cracks on the precast, prestressed planks (I think that's what you have,) should not be too wide. Can you post a photo?

Anyway, back to your question: traffic coating is usually used on parking garage decks. It is basically an epoxy and the last layer has color and sand (different levels of sand roughness.) Cracks are routed and sealed prior to the coating. It's quite involved.

It's all specialty products and you need to find a sales representative and contractor that knows how to install it.

I would contact a waterproofing/restoration contractor in your area. They are the ones that do this type of work.

A DIY epoxy coating or similar may also work for this use? Contact a representative.

 

[Gearhead Jim]

We do have a slope to the door, but not enough. About 1 1/2" for the 20' distance. Water/snow melt flows toward the door but takes a long time to get there.
The cracks are in the topping and pretty narrow, you could get a razor blade into them but not much more. They mostly follow along the junctions of the prestressed slabs below, but not every slab edge has a crack in the topping above.

 

[strutaeng]

How's your headroom? Maybe do an additional topping to increase slope?

I know there's a lightweight leveling compound. I used it in one of my projects once. Maybe that won't work if pouring at a slope?

Maybe a lightweight repair mortar? Something like this:

https://assets.master-builders-solutions.basf.com/en-us/basf-masteremaco-n-400-tds.pdf

Maybe even a shower pan liner or Redgard or similar, since you already have slope under the mortar. This set-up is used a lot in restaurant environments.

 

[ConCretin]

There are waterproofing membranes designed to be placed over a structural slab and protected by a topping slab over it. I'd be surprised if this were a less expensive option than waterproofing your existing topping slab plus you'd have to accommodate the additional thickness of new topping slab at your existing doors and other elements.

Traffic bearing waterproofing would be similar in cost and difficulty to an epoxy floor. There is no reason you couldn't do it yourself.

If water is making it's way into your floor structure you want to correct the situation before it becomes a much more expensive problem especially if there is road salts involved.

 

[Garage Flooring]

A lifetime ago I was a commercial specialist at Allied Building Products. Some of their locations will have a 'Division 7 Commercial Waterproofing' group/department.

We typically used products like this on commercial structures: https://www.euclidchemical.com/products/construction-products/coatings/coatings-traffic-deck/

I have seen a lot of people do a lot of things to 'rig' these floors. It never ends up cheaper.

Also keep in mind joints, cracks and where the floor meets the wall is the toughest parts

 

[Gearhead Jim]

We got the job done, it was expensive but perfect.
Member here "bamalamwv" sent me a PM asking details but I don't have enough posts to give him a PM reply.
If he sees this new post, please post your email or phone so I can contact you.

Cliffs Notes:
Garage floor repair place fixed the cracks, epoxy slurry to seal everything including floor-to-foundation joints. Another layer of slurry with those multi-colored plastic flakes + aluminum oxide grit for traction.
Now in our second winter. No cracks, no chips, no leaks, floor looks beautiful.