Garage floor and driveway replacement issues 1

[mcdermott2]

We recently had our garage floor (22x24) and outside slab (22x20) replaced due to severe
cracking and settling (the slab drained rainwater toward the house). We have heavy clay soil in
central Iowa. We requested a 5 inch pour with rebar, that the garage floor slope toward the
garage door and that the cement truck not drive on our asphalt driveway.

The day of the pour, the temperature was in the 90’s, and the cement was buggied from the street (approx. 300 ft.) and
the project was poured on 2 separate days. It rained within 1-2 hours of completion of the
outside slab (which was covered with plastic). We are unsure how long the total pour took. The
rebar was not placed on chairs but was “lifted” with a hook (supposedly).

The result we obtained is a garage floor that drains toward the door to the attached house,
pooling against the house’s foundation and making a small lake where one steps out of the
house, as opposed to draining toward the garage door. The outside slab has many dips and
irregular areas. The final section completed is especially rough/pocked.

Questions:
1) Is there any remedy or surface treatment we could apply to change the slope of a
concrete garage floor to direct water away from our house?
2) Is there a surface treatment that can fill in or even out dips and rough patches on the
outside slab? Will roughness impact the longevity of the concrete?

 

[mcdermott2]

An additional picture

 

[oldestguy]

Question: Where does that water come from? I assume rain outside. Certainly you don't wash a car in there. If it comes in from outside the door, a few things can be considered. I've seen folks cut out a part of the outside slab and install a slight bump. However, regardless consider either just inside or outside the door cutting out the slab and install a trench drain with grate. Drain that to a dry well off to the side away from the house. I'd only attempt to drain water that otherwise might come from rain on the surface or melting snow. Back sight being better than foresight, any job like this should have had grades set to get the drainage you want, especially if you had troubles to begin with. A dry well holds the water and allows slow infiltration to the subsoil. For a tight clay, I'd make that dry well as large as possible, area wise. A common dry well is a heavy walled Plastic tub with holes cut in it, filled with gravel. Without the tub, a hole filed with gravel and a perforated plastic pipe can do it also. It would not be used for draining car wash water or any large quantity. It is only to keep water out of the garage.

On the procedure used for placing the concrete, I doubt that it has any negative aspects.

For the inconvenience of water standing next to house wall or door, there can be a thin sand-cement grout overlay applied, but it will be an obvious patch. That takes roughening the surface and applying a thin grout. Surface must be bone dry and free of dust. Immediately before placing "patch" apply a paste consistency of Portland cement and water (that's the glue).

Assuming you had a proposal or estimate or some form of contract, taking the "bull by the horns" you could ask for a new slab, properly done.

 

[oldestguy]

OG again: The finished walls coming down to the slab place a severe restriction on what one can do for proper drainage. One option for the replacement would be a central floor drain. However, most building codes do not allow connecting that to a sanitary sewer. At my house the former owner was severely handicapped and got an OK from the city to have floor drains going to the sanitary sewer so he could wash his car in the garage. You might check that out.

On the question of the outside slab being rough, chances are no problem in the future due to that finishing.

 

[LittleInch]

Try looking up epoxy screed or mortar.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[oldestguy]

OG again:
Sitting over here in Wisconsin this PM and looking at the photos again it is my opinion you really are asking for something that is not possible due to those finished walls sitting at the same elevation as the door to outside without major work. Either lower the drainage area (garage door), create an inside drain or consider a major interior wall finish change. That change would be replacing the bottom section of those finished walls with a concrete curb. Then you can raise the inside surface with that thin overlay. I'd just do the trench drain at the garage door and live with it. Blame who ever built the place with interior finished walls so low in bottom elevation that you are now stuck with a problem.

 

[jike]

If water is coming under the garage door, then I agree with others that a section would have to be cut out and repoured with a trench drain outside and at least a 1/2" stepdown lip at the outside face of the garage door. The new section should be large enough to positively slope all new concrete to the trench drain. Connect the new trench drain as other posts have described. Make sure your garage door has a good rubber seal on the bottom.

It is possible for water to still puddle on the floor inside the garage from a wet vehicle dripping on the floor. If this is a problem that evaporation cannot take care of satisfactorily, a section of floor can be cut out, repoured and positively sloped to a drain.

The more difficult problem is at the finished walls. I assume that they are setting on a wood plate at the garage floor level. They really should be sitting on a concrete curb. Is it feasible to pour on concrete curb adjacent to the inside face of the wall? If so, it should be doweled to the existing slab and waterstopped to prevent water from flowing underneath. Unfortunately, this would probably have to be at your cost.

 

[mcdermott2]

Thanks for the great analysis! I will review these comments with my family and let you know if we have any additional questions / follow up.

 

[TehMightyEngineer]

Regarding the roughness and surface treatments; there's no good way to do this that would be perfectly aesthetically pleasing in my mind. It would be an obvious patch or repaired area. From a utility standpoint, roughness due to an irregular finish (assuming it was entirely due to the rain and proper finishing procedures were followed) would not be a problem for durability on a garage driveway. If it were mine I'd not worry about something like this. Maybe apply a fix to the finish if it needs other maintenance down the road (gets a crack or something) but for a new slab it's not worth it in my mind.

If I had to try to improve it I would fill in any roughness with a high strength pavement repair concrete. These come in premixed bags and could be prepared in buckets with a drill and paddle mixer. Trowel on it per the instructions, note how oldestguy referenced a skim coat of cement paste. Let cure and I'd then go to a local equipment rental company and get a hand concrete grinder or a wheeled push grinder. Use these to feather the edges of your repair and to smooth out any uneven areas. Watch a couple of YouTube tutorials on the operation of this equipment and look at some before and after pictures of what grinding does to the appearance of the concrete. Wear a dust mask, silicosis is no joke. If you've never worked with concrete it can cause chemical burns, wash any off your hands promptly.

Without seeing the concrete and seeing what your agreement with the contractor was, it's hard to tell if this is something they should pay for. From what it sounds like I don't believe they would be required too. I'd ask to see if they will as a customer service (or at least maybe they'll give you a favorable price on doing the work) but I wouldn't expect to get much.

Ian Riley, PE, SE
Professional Engineer (ME, NH, MA) Structural Engineer (IL)
American Concrete Industries

https://www.facebook.com/AmericanConcrete/

 

[Compositepro]

Is there a rain gutter above the garage door? If not, this is certainly the first thing to fix. You do not have much slope away from the garage and any ponding in front of the door will get into the garage. Wind driven rain will hit the door and run down, not onto the driveway, but onto the lip of the garage floor where the garage door seals. A tight foam rubber seal at the bottom of the door may help a lot. Ideally the garage floor should have a good slope at the door so water drains out, but this is difficult to fix after the fact.

Much can be learned by actually observing the water entering during rain to see what needs to be fixed. Spray a garden hose against the door if you do not want to wait for rain, but this will not tell you every thing. You may not have adequate drainage outside the door during heavy rain.

 

[Ron]

The first question I would ask is why did you allow such substandard construction? Where were you when the concrete was placed? Who supervised the subgrade preparation prior to placement? You indicated that the rebar was not placed on chairs. Why not?

I don't mean to be unkind, but for a structural engineer (at least your handle implies you are a structural engineer), you have not been exposed much to construction. First of all it is not "cement". It is concrete. It has proper procedures for delivery, placement, finishing and curing. All of these must be done properly to achieve quality concrete. You apparently engaged a concrete "contractor" to do a job with some very general specifications. Not good.

Hopefully you haven't paid the contractor for the work. Adding a topping to re-slope the floor and correct the placement mistakes is money that should not have to be spent. The result will be less than desirable. Since this is a residential application, you'll probably get someone of the same level of competence as the first contractor.

Have the contractor remove and replace the slab. Such construction is not acceptable, even by residential standards.

 

[mcdermott2]

Thanks, Ron,

Straight for the jugular! To give some context, this wasn't a project that I oversaw - this was a project that members of my family took on (who are not structural engineers). Considering the outcome of their project I offered my advice on how to proceed, and suggested that we post their issue to this forum for some additional perspective beyond my experience.

 

[oldestguy]

OG again: Here is a copy of a statement I made on July 15.

it is my opinion you really are asking for something that is not possible due to those finished walls sitting at the same elevation as the door to outside without major work

I differ with Ron. Getting that re-done is much simpler said than done with the current walls on the slab situation.

A significant court battle may come about if one insists on proper slope for drainage at reasonable cost when the agreement likely is a handshake at best.

 

[mcdermott2]

Thanks, All,

The feedback was very helpful! The contractor has agreed to attempt a fix. They are going to look at potential replacement of the slab, but as OG has indicated they will need to review the feasibility of providing a slope considering the finished walls.

 

[Ron]

mcdermott2....thanks for the clarification. Didn't mean to be harsh, just have a few pet peaves about terminology and I deal with construction defects on a daily basis in my forensic practice. My tolerance is low!

My concern about a repair using a topping is that your situation will require that the topping be feathered to the edge of the garage. This is certainly not good for trafficked slabs such as a garage. It isn't even good for non-traffic slabs if there is exposure to wetting/drying or thermal cycles.....they flake off at the edges without extraordinary surface prep, which most residential contractors don't have a clue how to accomplish. Given those issues, my recommendation is removal and replacement with specifications that directly address the issues at this site and acceptable concrete practices.

 

[oldestguy]

As usual Ron's advice is very valuable and, for an overlay, the warning should hit home. If, the contractor decides to go to the overlay, be aware that all the steps necessary cannot be left to an inexperienced contractor, but needs one that has done this before and can show examples of his work. There are companies that do thin overlays but their methods are pretty much secret, sometimes patented. Of the overlay projects I have been involved with, none are thin, but usually at least a few inches thick AND THE SURFACE PREPARATION IS VERY IMPORTANT, NOT JUST ADDING CONCRETE. Done wrong and you end up with more problems than before.