Preparing for slab pour and sealer application

[lyonkster]

My builder is planning to have the garage slab poured next week. I plan to apply Densifier and Ghost Shield 8510 after the concrete cures. What (if anything) should I ask for in the finishing process - power vs hand troweling, water application during pour/cure, etc? I just want to avoid any oversight that will make the Ghost Shield application more difficult. Thanks!

 

[ConCretin]

I'm sure the experts will chime in but one important point is to avoid chemical curing compounds. They will interfere with future sealer/densifier applications. My guess is that your weather conditions up there are probably conducive to curing but moist cure the slab if you do anything.

I'd keep the mix water low by using a mid range water reducer and I wouldn't want any water applied during finishing. It shouldn't be necessary especially this time of year and it will diminish your slab surface.

I'd definitely want my slab machine troweled. I'd be looking for a dense, smooth surface with no trowel marks or shine. The terminology varies but something akin to a 'smooth or flat troweled' finish and probably not a 'burnished or burnt' finish. A shiny floor is slippery and I suspect your sealer and densifier won't penetrate as well.

Give my Guide to Floor Slabs in the link below a read for some additional thoughts on the process. Congrats on the new garage and good luck with your floor.

 

[Rusted Nut]

Excellent advice from ConCretin. In the PNW the terminology is: float and smooth trowel. What you don’t want is a “hard trowel”, hard trowel will get a shiny slick surface.

 

[lyonkster]

Thanks @ConCretin and @Rusted Nut! @ConCretin, I read your Guide to Floor Slabs a while back, but just went back to refresh myself.

So I think I'll ask for the following:

- #4 bars, 24" o.c. supported at 4';
- 5" slab, 4000 psi concrete with fibermesh;
- 3/4" aggregate;
- mid range water reducer;
- no chemical curing compounds;
- no water added during finishing;
- dense smooth finish, not hard trowel or burnished;
- saw cuts every 12' in one direction (37' width) and 9' in other direction (27' depth)

Do I have this right? Did I miss anything? I have to say that I'm not finding much information on the distinction between "smooth finish" and "hard trowel" finish - can you share a link or some pics?

I'm working through a GC, so I'm thinking that I should have this discussion with him rather than with the concrete sub, right? I always worry about coming across as a "know it all" which I'm sure no professional likes - then again, with concrete, I can't wait to see what he does only to discover that it's not what I wanted, right?

 

[ConCretin]

So I think I'll ask for the following:

- #4 bars, 24" o.c. supported at 4';
- 5" slab, 4000 psi concrete with fibermesh;
- 3/4" aggregate;
- mid range water reducer;
- no chemical curing compounds;
- no water added during finishing;
- dense smooth finish, not hard trowel or burnished;
- saw cuts every 12' in one direction (37' width) and 9' in other direction (27' depth)

Do I have this right? Did I miss anything? I have to say that I'm not finding much information on the distinction between "smooth finish" and "hard trowel" finish - can you share a link or some pics?

I'm working through a GC, so I'm thinking that I should have this discussion with him rather than with the concrete sub, right? I always worry about coming across as a "know it all" which I'm sure no professional likes - then again, with concrete, I can't wait to see what he does only to discover that it's not what I wanted, right?

Assuming you have a fixed price contract, the first thing you should do is determine what that includes by talking to your GC. You can't go wrong with that formula if executed properly but frankly, I doubt that's what your GC intended to provide. One area where you could save a few bucks would be the reinforcing. Rebar has its advantages but that comes with a cost. Most slabs will perform just fine with welded wire fabric.

 

[lyonkster]

Assuming you have a fixed price contract, the first thing you should do is determine what that includes by talking to your GC. You can't go wrong with that formula if executed properly but frankly, I doubt that's what your GC intended to provide. One area where you could save a few bucks would be the reinforcing. Rebar has its advantages but that comes with a cost. Most slabs will perform just fine with welded wire fabric.

We have a cost plus contract. The original estimate was 4" slab, #3 rebar. Would 5" slab and #4 rebar be significantly higher (I've asked the contractor but haven't heard back)? Are any of the other items significant cost drivers?

 

[Rusted Nut]

Yes, 5” slab is 25% more concrete.

Personally I wouldn’t use fiber. I don’t think it works that well, and you’ll have to run a sander over it to get rid of the fuzzies. ConCretin has great info on minimizing cracking.

 

[Treeman]

Any floor drains and grades to specify?

 

[lyonkster]

Yes, 5” slab is 25% more concrete.

Personally I wouldn’t use fiber. I don’t think it works that well, and you’ll have to run a sander over it to get rid of the fuzzies. ConCretin has great info on minimizing cracking.

I think the slab thickness will be hard to change at this point, as the rock is already installed and compacted to a level assuming a 5" slab. I realize there'll be a 25% extra cost.

Thanks for the thought about fiber, I'll skip it!

 

[lyonkster]

Any floor drains and grades to specify?

I asked for about 1/8:12 slope towards the front doors.

 

[Pompey]

Don' forget to put a slope on the area in front of the doors to prevent water running back under the closed doors

I forgot and had to grind mine after the event...it was not fun

Should I Use a Concrete Surface Grinder or Angle Grinder on Garage Porch Slope

I recently installed a 35 x 60 metal building. It has five 12 foot roll up doors. The doors are set back about 6 inches from the edge of the concrete slab. I have been having problems with water getting under the doors. I now realize that the problem is the six inch deep concrete porch in front...

www.garagejournal.com

 

[lyonkster]

Don' forget to put a slope on the area in front of the doors to prevent water running back under the closed doors

I forgot and had to grind mine after the event...it was not fun

Should I Use a Concrete Surface Grinder or Angle Grinder on Garage Porch Slope

I recently installed a 35 x 60 metal building. It has five 12 foot roll up doors. The doors are set back about 6 inches from the edge of the concrete slab. I have been having problems with water getting under the doors. I now realize that the problem is the six inch deep concrete porch in front...

www.garagejournal.com

Thanks for the tip @Pompey. I read about your fiasco, that definitely did not look like fun, so I'd rather avoid the same situation.

Was your slab completely flat? My slab is supposed to have 1/8"-1/4" slope per 12", so hopefully that will avoid the water intrusion issue? But I will mention the concern to the builder before they pour concrete next week, I definitely don't want to be grinding brand new concrete!

 

[Garage Flooring]

I will let the concrete experts deal with the concrete itself.

8510 can be installed over power-troweled or hand troweled concrete so long as no sealer or curing agent with sealer is used.

The methods do vary slightly.

Etch & Seal Polyurea is also a great option

 

[Pompey]

Yes my pad was completely flat which I prefer. It looks like I have finally cured my door leaks. Since most of the front side of the building is actually door openings with small door pillars (60 foot long wall with four 12 foot doors), I am glad that the area under the front walls are flat and the door openings are sloped now. So if you put a slope on the door opening make sure the other areas where the walls will sit are flat unless you want to shim the wall plate or cut the wall joist ends at an angle.

Last week I had to regrind a few door areas to fix some very minor water leaks but this time I did not have to do a lot of grinding and I did it wet to keep the dust down. I watched a YouTube video about floor sealing and the author mentioned getting water under his doors and yes he had made the same mistake as I did with a flat porch.

I now have to deal with all the tree pollen and grinding dust remnants and then start on sealing the floors with 4500 and 8510.

Good luck with your pour.

PS I went with a 6 inch thick floor which is the minimum quoted for a two post lift.

 

[lyonkster]

Yes my pad was completely flat which I prefer. It looks like I have finally cured my door leaks. Since most of the front side of the building is actually door openings with small door pillars (60 foot long wall with four 12 foot doors), I am glad that the area under the front walls are flat and the door openings are sloped now. So if you put a slope on the door opening make sure the other areas where the walls will sit are flat unless you want to shim the wall plate or cut the wall joist ends at an angle.
...

Good luck with your pour.

PS I went with a 6 inch thick floor which is the minimum quoted for a two post lift.

Thanks, I'm crossing my fingers the pour will go well. I'm sure they know what they are doing, but I do want to confirm that they put the saw cuts where I want them (or tell me why that won't work and provide an alternative approach).

Since my slab is supposed to be slightly sloped, hopefully I won't have the same issue you had in front of the garage door, but I'll see if they can slope the 8" portion outside the garage door a little more than the rest of the slab.

In our case, the slab is being poured separately from the stem walls (which have already been poured and walls installed on top), so the slab slope will not affect the wall placement (but that's a good thing to keep in mind for anyone planning to build the walls directly on a sloped slab).

I'm going with a 5" slab - probably overkill since I'm planning on a four post lift, but whatever .

 

[lyonkster]

8510 can be installed over power-troweled or hand troweled concrete so long as no sealer or curing agent with sealer is used.

The methods do vary slightly.

Etch & Seal Polyurea is also a great option

Thanks @Garage Flooring , I'm glad you mentioned the polyurea. Since starting this thread, I've talked myself out of 8510, I think I'll be too worried about stains from oil and other fluids. So I'm now leaning towards coatings, looking at TS210 and single component polyurea. My primary considerations are stain resistance, next is application difficulty and slip resistance, and cost is less important (not that I'm not budget minded, but I'm in the "buy once cry once" mindset these days). What would be your recommendation?

 

[Garage Flooring]

For me, I would do an etch and seal kit. Some vendors are selling without etching, I don't suggest it. We have benen down that road before.

ETCH & SEAL Clear Garage Floor Coating & Sealer Kits

Transform your garage with the clear garage floor coating for a stunning high-gloss finish! Easy to install and incredibly durable, order now!

www.garageflooringllc.com

 

[dcg9381]

Thanks @Garage Flooring , I'm glad you mentioned the polyurea. Since starting this thread, I've talked myself out of 8510, I think I'll be too worried about stains from oil and other fluids. So I'm now leaning towards coatings, looking at TS210 and single component polyurea. My primary considerations are stain resistance, next is application difficulty and slip resistance, and cost is less important (not that I'm not budget minded, but I'm in the "buy once cry once" mindset these days). What would be your recommendation?

Polyurea is my go to, I've done 4 floors with it. It may require additional prep though (ask vendors). It's excellent at resisting most fluids short of something like acetone/keytone... You can make it look like anything you want via a combination of solid colors and/or a base stain of the concrete when using a transparent application. The lower floor of my home is actually finished in polyurea. Easier to apply than epoxy (IMHO). Less expensive too.

It is slippery as **** when wet. You address this by adding an anti-slip agent on the final coat.

 

[Garage Flooring]

Polyurea is my go to, I've done 4 floors with it. It may require additional prep though (ask vendors). It's excellent at resisting most fluids short of something like acetone/keytone... You can make it look like anything you want via a combination of solid colors and/or a base stain of the concrete when using a transparent application. The lower floor of my home is actually finished in polyurea. Easier to apply than epoxy (IMHO). Less expensive too.

It is slippery as **** when wet. You address this by adding an anti-slip agent on the final coat.

It can definitely me slick! All
Of our kits include anti skid

 

[Pompey]

Since my slab is supposed to be slightly sloped, hopefully I won't have the same issue you had in front of the garage door, but I'll see if they can slope the 8" portion outside the garage door a little more than the rest of the slab.

My porch was about 7 3/4 inches deep I think and I dropped (ground down) the front by about 1/2 inch. It seems to have stopped pretty much all of the leaks now.

 

[lyonkster]

Thanks @Garage Flooring and @dcg9381 ! I think polyurea is looking like a good option for me (I value stain resistance most).

For tomorrow's pour/finishing, would polyurea require anything different than if I went with Ghost Shield like I planned originally? I think they plan to power trowel (like I asked them to), would that be OK with a polyurea (I'll make sure to ask that they don't burnish it)?

 

[lyonkster]

My porch was about 7 3/4 inches deep I think and I dropped (ground down) the front by about 1/2 inch. It seems to have stopped pretty much all of the leaks now.

Thank you, that's a good data point!

 

[Garage Flooring]

Thanks @Garage Flooring and @dcg9381 ! I think polyurea is looking like a good option for me (I value stain resistance most).

For tomorrow's pour/finishing, would polyurea require anything different than if I went with Ghost Shield like I planned originally? I think they plan to power trowel (like I asked them to), would that be OK with a polyurea (I'll make sure to ask that they don't burnish it)?

Power trowel is fine. Just make sure no sealer is added. You may need a little more etching than what’s in the kit for a power troweled floor

 

[lyonkster]

The slab is all done - light power trowel followed by hand troweling. Then the saw cuts were made the next day.

I have a question about the saw cuts - the edges of the cuts are fairly sharp (understandably) - would there be a benefit to trying to break the sharp cut edges somehow, to avoid future spalling? Or am I overthinking it?

 

[theoldwizard1]

IMHO ... every garage/shop floor should have the following ...

• Vapor barrier between the concrete and the dirt. This will keep moisture out in the future.
• Curbing (except in front of garage door). It won't 100% eliminate water ingress, but it will slow it down. This is required in some jurisdictions.

Something I would discuss with the concrete guys is "drainage". No slab is ever perfectly level. You would probably prefer to have it "drain" toward the main door.

 

[lyonkster]

IMHO ... every garage/shop floor should have the following ...

• Vapor barrier between the concrete and the dirt. This will keep moisture out in the future.
• Curbing (except in front of garage door). It won't 100% eliminate water ingress, but it will slow it down. This is required in some jurisdictions.

Something I would discuss with the concrete guys is "drainage". No slab is ever perfectly level. You would probably prefer to have it "drain" toward the main door.

Thanks, I think we have these covered - 10 mil vapor barrier under slab, 1/8:12 slope towards the front. What is "curbing"?

 

[theoldwizard1]

What is "curbing"?

The walls sit on a concrete curb, usually about 6" above the floor.

 

[lyonkster]

The walls sit on a concrete curb, usually about 6" above the floor.

Understood, thanks. Our walls are built on top of concrete stemwalls (separate from the slab), so we have at least a 6" concrete curb all around:

 

[Pompey]

Looks good and I see that he sloped the door openings as well. You should be good there.

 

[lyonkster]

Looks good and I see that he sloped the door openings as well. You should be good there.

He said did, thanks for the suggestion!

 

[Pompey]

Here's the finished job on my door openings...well I hope it's finished

 

[ConCretin]

I have a question about the saw cuts - the edges of the cuts are fairly sharp (understandably) - would there be a benefit to trying to break the sharp cut edges somehow, to avoid future spalling? Or am I overthinking it?

It's generally not a problem. The saw kerf is pretty narrow and not likely to spall from cross traffic. Plus it would be fairly difficult to ease the edges of the cut.

 

[lyonkster]

It's generally not a problem. The saw kerf is pretty narrow and not likely to spall from cross traffic. Plus it would be fairly difficult to ease the edges of the cut.

That is sense, thanks!