# Concrete garage floor



## ContractorStevv (Aug 10, 2019)

Any tips to reduce the chances of having a concrete floor damaged by frost in a cold climate? My father poured a concrete garage floor on less than ideal soil and after 20 years it still looks as good as the day it was poured.


----------



## Randy Bush (Mar 7, 2011)

ContractorStevv said:


> Any tips to reduce the chances of having a concrete floor damaged by frost in a cold climate? My father poured a concrete garage floor on less than ideal soil and after 20 years it still looks as good as the day it was poured.


Blankets. And go well past the edges with them . Some might disagree , but I think the concrete we had back then was better stuff. Not so prone to cracking, stuff today seems to crack fairly soon .


----------



## We Fix Houses (Aug 15, 2007)

Mike Day Concrete a few days ago in sub freezing temps. A lot of pointers on this one.






I did leave a comment about adding 1/4" Dow fanfold styrofoam as a thermal break (.25 sq ft) to the gravel base. He mentions things would move along quicker with it.


----------



## ContractorStevv (Aug 10, 2019)

^ I don't think I made myself clear. It's not the pour that concerns me, b/c I'll be pouring next spring when temps are warm. It's keeping the concrete intact for years to come. Some garage floors crack, others look like new and last forever. Those that crack usually do as a result of frost heaving. I'm just wondering what I can do to reduce cracking, uplifting etc.


----------



## We Fix Houses (Aug 15, 2007)

Mike Day's website

https://www.everything-about-concrete.com/concrete-expansion-joints.html

Keep an eye on David Odell Concrete too
https://www.youtube.com/channel/UC5y5SeEYvz_MqPmBU_zLTyA/featured


----------



## Texas Wax (Jan 16, 2012)

Properly worked, tooled and finished is key. Pushing aggregate down pulling sand and cream up at the right times. 

And low/no chert mix. Fine stone that absorbs water then freezes and pops. Another if your in the rust belt (salted roads in winter), sealing- keeping the salty slush and slop off the floor makes a big difference.


----------



## griz (Nov 26, 2009)

ContractorStevv said:


> ^ I don't think I made myself clear. It's not the pour that concerns me, b/c I'll be pouring next spring when temps are warm. It's keeping the concrete intact for years to come. Some garage floors crack, others look like new and last forever. Those that crack usually do as a result of frost heaving. I'm just wondering what I can do to reduce cracking, uplifting etc.


proper substrate, low slump, do not add water, keep additives to a minimum, do not over work it and a SLOW wet cure...:thumbsup:


----------



## Railman (Jan 19, 2008)

One constant to concrete...it cracks!
It can be caused by a lot of variables.
1)Weak mix.
This can be from a variety of reasons including poor mix ratio, long trips from plant resulting in hot mix, pouring in hot weather resulting in mix loosing hydration too soon, watering down mix at site, over working when mix is trying to cure. Not keeping hydration during days following pour, just to name a few. 
2) Substrate problems.
Pouring on frozen ground, non or uneven compaction, hydraulic pressure from below, extreme temperature changes. I've seen summer time hi-ways expand so much that they buckle up at the joints so bad, that the road had to be closed down due to ramping and mis-matching at joint. I believe this is caused by the surface drying out, while the bottom of crete is still moisture laden. This action is very similar to what happens to a hardwood floor in the winter when the homes' humidity drops a lot in a short period of time. It results in a corduroy surface in wood, & concrete. Basement floors are highly susceptible to this. The solution is smaller size slab pieces to control the cracks, and visqueen (sheet plastic) under slabs.

Basically, best bet ... Do what Griz just posted above!


----------



## NYCB (Sep 20, 2010)

ContractorStevv said:


> ^ I don't think I made myself clear. It's not the pour that concerns me, b/c I'll be pouring next spring when temps are warm. It's keeping the concrete intact for years to come. Some garage floors crack, others look like new and last forever. Those that crack usually do as a result of frost heaving. I'm just wondering what I can do to reduce cracking, uplifting etc.


It's all in the base prep and exterior grade/drainage.

Keep water from getting under it to begin with, and you won't have frost getting under it.


----------



## NYCB (Sep 20, 2010)

griz said:


> proper substrate, low slump, do not add water, keep additives to a minimum, do not over work it and a SLOW wet cure...:thumbsup:


The only time I've ever seen a wet cure is the DOT guys with bridge decks.

We usually just spray everything down with cure and seal once finishing is complete and call it a day.

I just saw a floor I poured 6 years ago the other day, it' has a bit of wear where they drive in with salty tires, but the rest still looks good.


----------



## Golden view (Feb 16, 2012)

griz said:


> proper substrate, low slump, do not add water, keep additives to a minimum, do not over work it and a SLOW wet cure...:thumbsup:


More specifically/scientific than low slump and do not add water: Spec and keep to the W/C ratio low.

Water is the main reason concrete shrinks. Even dry mixes have more water than the cement needs for the hydration reaction. The rest evaporates, leaving less volume in the same place. In other words, shrinking.


----------



## Golden view (Feb 16, 2012)

As far as the freeze cycle protection, look into sir entrained concrete.


----------



## builditguy (Nov 10, 2013)

Thought about this, a little. I think you are referring to the crack that shows up down the middle? I've seen this in older garages. The frost heaves up the middle, but the walls sit on the perimeter and it's a little heavier.

For a floating slab garage, we pour a rat wall around the perimeter and 1/2" rebar grid in the floor. A 6" slab will go a long way over a 4" floor.


----------



## NYCB (Sep 20, 2010)

builditguy said:


> Thought about this, a little. I think you are referring to the crack that shows up down the middle? I've seen this in older garages. The frost heaves up the middle, but the walls sit on the perimeter and it's a little heavier.
> 
> For a floating slab garage, we pour a rat wall around the perimeter and 1/2" rebar grid in the floor. A 6" slab will go a long way over a 4" floor.


Cracks will occur in any slab that isn't cut.

Just have to make it crack neat so get there early the next morning and get it cut.

I need to buy an early entry saw, I had a very large floor start cracking on me before we even got done finishing it this summer, kind of sucked, but I was able to catch a few of them the next morning. Nothing I could do about it, I told them we needed the deck on first to keep the sun off it, didn't want to do it.


----------



## TimNJ (Sep 7, 2005)

ContractorStevv said:


> ^ I don't think I made myself clear. It's not the pour that concerns me, b/c I'll be pouring next spring when temps are warm. It's keeping the concrete intact for years to come. Some garage floors crack, others look like new and last forever. Those that crack usually do as a result of frost heaving. I'm just wondering what I can do to reduce cracking, uplifting etc.


If the backfill isn't settled and compacted all the way it's going to crack down the road.
Real common to see cracked garage slabs around here. Areas close to the foundation wall of the house were excavated to basement depth for the footings then backfilled.
Builders are pushing so fast that backfill never settles and presto! slab cracks.


----------



## Fishindude (Aug 15, 2017)

griz said:


> proper substrate, low slump, do not add water, keep additives to a minimum, do not over work it and a SLOW wet cure...:thumbsup:


This, plus saw cut expansion joints in proper locations as soon as slab is hard enough to run the saw on. Waiting till the next day is too late.


----------



## eastcoastjoe (Feb 27, 2019)

TimNJ said:


> If the backfill isn't settled and compacted all the way it's going to crack down the road.
> Real common to see cracked garage slabs around here. Areas close to the foundation wall of the house were excavated to basement depth for the footings then backfilled.
> Builders are pushing so fast that backfill never settles and presto! slab cracks.


Agreed, most good excavators around here compact every foot of fill going back into the garage. Some builders don't want to pay for that and just hose it down for a few weeks. Those slabs usually crack like crazy.


----------



## NYCB (Sep 20, 2010)

eastcoastjoe said:


> Agreed, most good excavators around here compact every foot of fill going back into the garage. Some builders don't want to pay for that and just hose it down for a few weeks. Those slabs usually crack like crazy.


I won't do any exterior slabs over a freshly backfilled house.

Let it get a year of rain and snow, then I'll come back and get a good base put in.

Amazing how far it can drop after freezing and thawing a few times.


----------



## dayexco (Mar 4, 2006)

concrete cracks. you put saw cuts in to put cracks where you want them.


----------



## Randy Bush (Mar 7, 2011)

dayexco said:


> concrete cracks. you put saw cuts in to put cracks where you want them.


And I have seen it crack beside in the joints / saw cuts.


----------



## dayexco (Mar 4, 2006)

At home they're cutting the 2nd they can walk on it. They also had me keep my shop floor damp for a week after they poured it.

We used same design mix as on interstate highways and had no cracks other than cut ones. 

Sent from my SM-G950U using Tapatalk


----------



## builditguy (Nov 10, 2013)

We try to get our control joints as good as possible. 25% the depth of the slab and 1.5 times the thickness.

I don't have a soft cut saw. Personally, I don't like cutting it that soon. The edges of the cut tend to flake off. Maybe flake off isn't the way to explain it, but it's a rough edged cut.
I will cut it the next day. Also have someone running a blower, as I cut. Doesn't affect the cut, but it does keep the concrete powder from sticking to the slab. We don't have to clean it off that way.

I thought he was talking about cracks that develop, over time, and continually get worse. Like a 24' x 24' garage with a 16' door. I've seen slabs get really bad cracks, right down the middle. Floating slabs only.
Of course the really bad ones I've seen are 20 years old. And, so far, luckily, none of mine. I think the 2' x 2' rebar grid pays off.


----------



## rjconstructs (Apr 26, 2009)

I have to question pouring in cold weather like that. A general rule here is the temp must be 40 degrees and rising. I know there are additives to reduce the water / cement ratio - so the concrete even has a chance to set. Our weather can wildly fluctuate from day-to-day so we would probably hold off pouring at temps like that. They may not have that luxury in their area. I'd be leery of pouring on a frozen base though. It would be interesting to see what the garage slab looks like a few years down the road.


----------



## NYCB (Sep 20, 2010)

Randy Bush said:


> And I have seen it crack beside in the joints / saw cuts.


That happens every now and then, and it sucks, like the concrete giving you a big middle finger.


----------



## Fishindude (Aug 15, 2017)

If your slab cracks right alongside the control joints, they didn't saw cut the control joints soon enough. Probably did it the next morning.


----------

