Slab prep, winter coming, still questions...

[bmwpowere36m3]

Trying to finish before winter sets in (located in CT)... so far:

• Excavated, foundation poured, back-filled and compacted
• Rough framing complete
• Roof shingled
• Door/Window openings covered with plywood/tarp

Plan Forward:

• 15 mil vapor barrier, seams taped
• #4 rebar on 18" oc (concrete guy likes 12" oc)
• 3" plastic chairs 36" oc (Hercules)
• 24' Polylok trench drain
• 6" slab, no fiber, 4-5k PSI, power-troweled

Since I wasn't thrilled with the first concrete guys work (different reason), I've been looking for another. I found one and have spoken on the phone. Seems knowledgeable, mentioning: slump, admix for reduced water, vapor barrier, 12" oc #4 rebar or 4x4" 4-6 ga mesh etc...)

The foundation was poured such that the openings for doors are at or below bottom of desired slab. Thus the slab would sit on top of the stem wall at those openings. My father's garage foundation was poured the same way, by different guys, so I assume its the norm in the area.

This new concrete guy recommend tieing the slab rebar horizontally into stem walls by drilling and hammering in rebar. Thoughts? I didn't mention the slab on stem wall to him.

Second, does the vapor barrier around the edges need to be taped/adhered to the stem wall?

Third, every cross of rebar needs to be tied?

Keeping the cold out will be the challenge and getting everything done before it gets too cold (current highs 30s, lows 20s). Any final tips related to slab prep or cold weather? Thanks

 

[mcbane]

The main reason to dowel into the stem walls would be to avoid settlement, particularly if you have concerns about compaction right near the walls. But with only a 18" grid of rebar I wouldnt do it. If your slab wants to settle it may well crack due to forces at those dowelled in rebars. A bit of settlement might be better.

You only need to tie enough bar intersections to keep things from moving. Every 3rd intersection probably good enough for that.

No idea where you are and thus what you mean by "cold weather". I've done a few pours at 30-34 degrees F and the biggest problem I have had is running out of daylight before the concrete is ready to finish. So I would avoid scheduling the job to start in the afternoon.

 

[chaosracing]

Pinning the slab into the walls is not a bad idea. I have done that on a few projects. As for the concrete floor being poured over the wall at the openings, again, I prefer that option. Just make sure you pin the slab into the wall using L shaped rebar that is epoxied into the wall, unless some was left above the wall pour.
16" OC should be fine. 12" is for high strength applications and if your going to have heavy equipment in the garage. But rebar is cheap and easy to install now.
As for the vapor barrier being taped or not taped to the wall, I have seen it done both ways. Best thing I can say about that is ask the concrete guy what he prefers. When I did mine, I put down 1" polystyrene insulation with the joints taped. The concrete guy was a little less than thrilled (even though I told him well in advance that was the design) because it make the cure time a little longer due to water not being wicked out by the ground. He just wanted to get out quicker is what that came down to.

As for cold weather, cant help since no idea on location. Around me, there is no concern yet for cold weather. But later on, some will add stuff (like calcium flake) to the mix to help the concrete cure faster. Again, thats a conversation to have with your guy.

 

[bmwpowere36m3]

The main reason to dowel into the stem walls would be to avoid settlement, particularly if you have concerns about compaction right near the walls. But with only a 18" grid of rebar I wouldnt do it. If your slab wants to settle it may well crack due to forces at those dowelled in rebars. A bit of settlement might be better.

You only need to tie enough bar intersections to keep things from moving. Every 3rd intersection probably good enough for that.

No idea where you are and thus what you mean by "cold weather". I've done a few pours at 30-34 degrees F and the biggest problem I have had is running out of daylight before the concrete is ready to finish. So I would avoid scheduling the job to start in the afternoon.

If there is any settlement, then it'll likely crack at the thresholds since the slab will sit on directly on stem wall. Every third cross, will be secured with chair... so that's good. Cold weather, I'm located in Connecticut so 20-30s.

 

[bmwpowere36m3]

Pinning the slab into the walls is not a bad idea. I have done that on a few projects. As for the concrete floor being poured over the wall at the openings, again, I prefer that option. Just make sure you pin the slab into the wall using L shaped rebar that is epoxied into the wall, unless some was left above the wall pour.
16" OC should be fine. 12" is for high strength applications and if your going to have heavy equipment in the garage. But rebar is cheap and easy to install now.
As for the vapor barrier being taped or not taped to the wall, I have seen it done both ways. Best thing I can say about that is ask the concrete guy what he prefers. When I did mine, I put down 1" polystyrene insulation with the joints taped. The concrete guy was a little less than thrilled (even though I told him well in advance that was the design) because it make the cure time a little longer due to water not being wicked out by the ground. He just wanted to get out quicker is what that came down to.

As for cold weather, cant help since no idea on location. Around me, there is no concern yet for cold weather. But later on, some will add stuff (like calcium flake) to the mix to help the concrete cure faster. Again, thats a conversation to have with your guy.

Only pin the slab at openings? The first concrete guy installed some vertical rebar around the foundation from the footer, up thru the stem wall. In a few places he let it run wild and cut it after forms were removed.

Seemed sporadic and what little stuck out in the openings I trimmed flush to not get a flat while driving truck/skidsteer in/out during fill.

I just assuming they served no purpose for the slab... horizontally the slab isn't going anywhere as its contained by the walls and horizontal rebar that I'll lay inside.

I recall reading something stating that overlapping the seams by 12" or more in the vapor barrier is good enough... no need for tape. I planned to tape anyway, the question was about the stem wall/edge detail. Either:

• Cut VB flush with wall
• Extend VB up wall a couple inches
• Extend VB up wall a couple inches + adhere to wall with tape, caulk, butyl tape, etc...

 

[chaosracing]

Really the only place that needs to be pinned is the openings for doors. Other than that, pinning into the walls is like adding belts and suspenders. Your trying to create a monolitic structure, even though it is poured in stages. If you get water in between the pours and it freezes, this will help prevent heaving of the slab at the opening. Every concrete job I worked on or helped with, pins were always put in from the foundation into the slab at opening just like what your going to have. Also 90% of the time, the slabs were pinned into the walls as well.

 

[matt_i]

I let the slab float, but its in contact with the stem wall in 3 door locations. So far in year 4 that's not an issue.

I think I tied every other rebar crossing, then alternate on the next row, sort of like a chessboard. The basic thing is you don't want it to move when a guy walks on it or trips on it, etc. If you can walk all over it and it seems solid then I think its good. There can be a "bad spot" in the spacing if it happens to be one that constantly catches the workers' slush boots as they move around. I think your 18" oc is going to be just fine.

I would suggest looking at a curing sealer. I believe it will help your slab gain maximum strength without wet-curing it in the cold. The downside is it can interfere with future coatings but can be sanded off with extra labor. The upside is that its a pretty decent coating by itself.

Also make sure your contractor is on track to come back the next morning after the pour and saw cut the control joints. 10-12' squares.

My concrete guy told me he was OK with down to 28F overnight before he would be worried and would want to take precautions to insulate. I had the 2% CaCl added which lit the proverbial candle. Could look at a non chloride accelerator, it can give you incremental peace of mind on your rebar condition. With good prep and execution, in all likelihood it will not be a concern even for the next generation

 

[mcbane]

If there is any settlement, then it'll likely crack at the thresholds since the slab will sit on directly on stem wall...

At the thresholds your shear capacity is the full shear capacity of a 6" slab, which is considerably stronger than #4 dowels at 18" on center. People dowel slabs to walls all the time, I'm just of the opinion that it introduces a new risk and doesnt provide any significant advantage.

 

[bmwpowere36m3]

Really the only place that needs to be pinned is the openings for doors. Other than that, pinning into the walls is like adding belts and suspenders. Your trying to create a monolitic structure, even though it is poured in stages. If you get water in between the pours and it freezes, this will help prevent heaving of the slab at the opening. Every concrete job I worked on or helped with, pins were always put in from the foundation into the slab at opening just like what your going to have. Also 90% of the time, the slabs were pinned into the walls as well.

Hindsight... though the pieces he left sticking out were at best 2-3" long and maybe 2 of them in a 10' opening. No much good IMHO.

I dunno, everyone has a different take. My father's barn had no rebar doweling, 6" 5-6k PSI slab (sits on wall at thresholds), pretty thin wire mesh that was "pulled" up and no control cuts. After 4 yrs/winters and moving his class A RV in/out not a single noticeable crack.

With our current temps, if I was to epoxy set the rebar it'd need to cure in 20-30*F and sooner than later (risk missing pour oppurtunity this year).

 

[dcg9381]

I'm relatively new to concrete - and my soil conditions are different than yours, so grain of salt here:

4-5k PSI concrete, 6" slab - lot of concrete. I'm curious as to your beam design.
Around here, we do slabs like "tables" - at least that's how I think of the design. My residential garage foundation (going up now) has a 12" wall of concrete on the back side pier, as it's elevated, and 12 piers drilled 10' down, as it's sitting on stuff that may move around a bit.

My shop, 24" concrete - and neighbors slabs, 3500 psi concrete, and just use appropriate amounts of steel.

Rebar does degrade (eventually) but ask yourself - "in my lifetime?"

 

[ConCretin]

The foundation was poured such that the openings for doors are at or below bottom of desired slab. Thus the slab would sit on top of the stem wall at those openings. My father's garage foundation was poured the same way, by different guys, so I assume its the norm in the area.

This new concrete guy recommend tieing the slab rebar horizontally into stem walls by drilling and hammering in rebar. Thoughts? I didn't mention the slab on stem wall to him.

Second, does the vapor barrier around the edges need to be taped/adhered to the stem wall?

Third, every cross of rebar needs to be tied?

Keeping the cold out will be the challenge and getting everything done before it gets too cold (current highs 30s, lows 20s). Any final tips related to slab prep or cold weather? Thanks

Your questions in order;

Pouring the slab out through the door openings is standard practice. No problem there.

I wouldn't pin the slab around the perimeter. You are inviting cracks if you get any settlement. Let your base support the slab. In addition, perimeter dowels will restrain the slab from contracting, which will increase the likelihood of shrinkage cracks.

The vapor barrier should be turned up at the perimeter but don't worry about getting a seal.

Rebar only needs to be tied enough to secure it during placement. The ties perform no structural function. 50% at the most.

Btw, rebar does nothing to prevent cracks or make the slab stronger. There is much misinformation on this subject. Rebar actually increases the likelihood of cracks by restraining the slab from freely contracting with shrinkage. It's sole function is the same as wire mesh - to hold cracks together once they form. #4's at 18" is more than adequate for this function.

You don't mention control joints but you'll want them if you want to avoid ugly random cracks you can see. Better to hide the cracks at the bottom of some nice straight control joints.

Cold weather concrete is tricky. You need adequate temps to allow the concrete to set enough to permit finishing before the slab must be covered to protect it from freezing. This is more difficult inside a structure where it won't see any sun. Accelerating admixtures are a must. You need too be patient and pick your day. I'd be looking for daytime highs around 40 for an exposed slab and even then it's a **** shoot if temps drop below freezing the same day.

Concrete sets very slowly below 50 degrees or so. It will come from the plant warmer than that but will lose heat quickly once it is dumped on a cold sub grade.

A couple specific points. Don't place on a frozen sub grade. Keep the concrete at 55 degrees for at least three days by covering with blankets, hay, etc. Provide external heat if necessary but don't use unvented heaters. Don't worry about conventional curing unless concrete is exposed to heaters.

Take a look at my Guide to Floor Slabs in the link below for some additional thoughts and feel free to PM me if you have questions.

 

[wssix99]

^ Lots of great info there.

I wouldn't pin the slab around the perimeter. You are inviting cracks if you get any settlement. Let your base support the slab. In addition, perimeter dowels will restrain the slab from contracting, which will increase the likelihood of shrinkage cracks.

Absolutely. + More food for thought -> We don't find pinning a floating slab into walls in any concrete design guide or placement guide. There are lots of reasons for this. Until such a method shows up in a reputable reference, (ie: something more than the internet or "my guy said so") this is likely not a good consideration.

You don't mention control joints but you'll want them if you want to avoid ugly random cracks you can see. Better to hide the cracks at the bottom of some nice straight control joints.

This is really the key thing. A LOT of rebar can be used to make cracks thinner, but the thing that drives the design strategy is the control joint plan and spacing. Many slabs go off the rails because there is no plan for this or these are put in as an afterthought or are put in too late. The control joints should be figured out first and then everything works around them. (ie: 2 posts lift bases can't be placed by them, etc.)

 

[bmwpowere36m3]

I'm relatively new to concrete - and my soil conditions are different than yours, so grain of salt here:

4-5k PSI concrete, 6" slab - lot of concrete. I'm curious as to your beam design.
Around here, we do slabs like "tables" - at least that's how I think of the design. My residential garage foundation (going up now) has a 12" wall of concrete on the back side pier, as it's elevated, and 12 piers drilled 10' down, as it's sitting on stuff that may move around a bit.

My shop, 24" concrete - and neighbors slabs, 3500 psi concrete, and just use appropriate amounts of steel.

Rebar does degrade (eventually) but ask yourself - "in my lifetime?"

Not familiar with beams... the foundation consists of a perimeter trench dug to frost depth (42" below grade in CT) or more if not virgin soil or less if you hit ledge. The center is stripped of topsoil again till you hit virgin soil. Around here its a sandy material that starts beige and becomes light grey.

A footer, 18" x 12", is poured around the perimeter, on top of which a 10" wall is poured. In my case the wall extends 2' above grade to provide protection from water and have 10' wall, with 8' framing.

The center of the foundation is backfilled with appropriate fill and compacted. Since I removed a tree in the corner where the foundation was placed, I need quite a bit of fill in one corner. The other half of the garage needed little since it sat on ledge (the footer is 12" below at best).

I started with 3 1/2" process in a few lifts, then 6" of 1 1/2" process and finally another 6" of 3/4" process. Some areas have 12" of fill and others 36". I got a really good price on the 3 1/2" and 1 1/2" process from a local site that was processing material down the road from me. Since the price was very good, I scrapped the topsoil to extend driveway to garage and used the same material.

However the 1 1/2" process was a little difficult to work with and seemed to have less fines, so I decided to get some 3/4" process for the garage which was a little easier to work with. I tried for +/- 1/4" grade... not happening. Spent a few hours and got +/- 1/2" at best.

So long story short, the slab is only supported via the compacted base...

 

[bmwpowere36m3]

Your questions in order;

Pouring the slab out through the door openings is standard practice. No problem there.

I wouldn't pin the slab around the perimeter. You are inviting cracks if you get any settlement. Let your base support the slab. In addition, perimeter dowels will restrain the slab from contracting, which will increase the likelihood of shrinkage cracks.

The vapor barrier should be turned up at the perimeter but don't worry about getting a seal.

Rebar only needs to be tied enough to secure it during placement. The ties perform no structural function. 50% at the most.

Btw, rebar does nothing to prevent cracks or make the slab stronger. There is much misinformation on this subject. Rebar actually increases the likelihood of cracks by restraining the slab from freely contracting with shrinkage. It's sole function is the same as wire mesh - to hold cracks together once they form. #4's at 18" is more than adequate for this function.

You don't mention control joints but you'll want them if you want to avoid ugly random cracks you can see. Better to hide the cracks at the bottom of some nice straight control joints.

Cold weather concrete is tricky. You need adequate temps to allow the concrete to set enough to permit finishing before the slab must be covered to protect it from freezing. This is more difficult inside a structure where it won't see any sun. Accelerating admixtures are a must. You need too be patient and pick your day. I'd be looking for daytime highs around 40 for an exposed slab and even then it's a **** shoot if temps drop below freezing the same day.

Concrete sets very slowly below 50 degrees or so. It will come from the plant warmer than that but will lose heat quickly once it is dumped on a cold sub grade.

A couple specific points. Don't place on a frozen sub grade. Keep the concrete at 55 degrees for at least three days by covering with blankets, hay, etc. Provide external heat if necessary but don't use unvented heaters. Don't worry about conventional curing unless concrete is exposed to heaters.

Take a look at my Guide to Floor Slabs in the link below for some additional thoughts and feel free to PM me if you have questions.

Lots of good info...

He mentioned the importance of protecting the sub grade from freezing. For control joints, he recommended either sawcuts or zipstrips.

What is the concern with an unvented heater? The garage is detached and really sealed (only rough framing, open eaves, ridge vent, no insulation, openings covered with tarp to block bulk air movement).

What is conventional curing?

Also the rebar chairs I ordered (Hercules 912), place the bottom of the lower rebar at 3" and the top of upper at 4". With a 6" slab and the variations in the grade, what is the recommended and/or minimum cover over the rebar?

 

[ConCretin]

Lots of good info...

He mentioned the importance of protecting the sub grade from freezing. For control joints, he recommended either sawcuts or zipstrips.

What is the concern with an unvented heater? The garage is detached and really sealed (only rough framing, open eaves, ridge vent, no insulation, openings covered with tarp to block bulk air movement).

What is conventional curing?

Also the rebar chairs I ordered (Hercules 912), place the bottom of the lower rebar at 3" and the top of upper at 4". With a 6" slab and the variations in the grade, what is the recommended and/or minimum cover over the rebar?

Personally I prefer saw cut control joints as long as they are done with an early entry saw immediately after finishing because they tend to be straighter. The advantage of zip strips is that they go in during the placement so you don't have to wait for the concrete to set or uncover it again to cut control joints. They both perform the same function.

An unvented heater causes what is called carbonation, which can cause a weak chalky surface on the slab. While I was checking my spelling, I came across this article;

https://www.concreteconstruction.net/how-to/materials/carbonation_o

To be honest, slabs have been placed with space heaters for years and I've never seen a problem but it wouldn't be permitted on a spec job. A compromise might be to use a heater long enough to get the slab in and then cover it for protection.

By conventional curing I meant keeping the slab wet for a period of time to prevent premature drying. Unless the slab is exposed to hot dry air from heaters, its not really necessary this time of year. Concrete won't lose much moisture in cold weather conditions so it's not as big a concern as it would be in the summer. Just cover the slab to protect it from the cold and you'll be fine.

Your chairs should be just fine. Typically you want 2 or 3" cover to soil and 1 or 2" cover to exposed surfaces.

 

[matt_i]

Also the rebar chairs I ordered (Hercules 912), place the bottom of the lower rebar at 3" and the top of upper at 4". With a 6" slab and the variations in the grade, what is the recommended and/or minimum cover over the rebar?

I used 2" chairs, think they were GripRite ProLok, with my idea being that it is in the "bottom third" of a 6" slab.

When you load the plate (the slab) the bottom is in tension. And concrete don't do tension But the steel can help it, and still functions to keep cracks aligned.

 

[ConCretin]

When you load the plate (the slab) the bottom is in tension. And concrete don't do tension But the steel can help it, and still functions to keep cracks aligned.

So what happens when you load the perimeter of the slab where the top is in tension? A slab on grade isn't a beam where the bottom is in tension between supports and the top is in tension over the supports. It depends on uniform support from below to function.

Do not spend money on rebar in your slab in the mistaken belief that it is making your slab stronger because it simply isn't. Rebar performs the exact same function as wire mesh - it holds cracks together once they occur - it does not prevent them. The sole advantage of rebar over mesh is that it is easier to support because it is more rigid.

ACI recommends placing slab reinforcing as high as possible to keep cracks as narrow. It's a moot point anyway in the real world of 4 to 6" slabs. By the time you allow for adequate cover above and below, you are in the middle third of the slab anyway, including Matt_i's example of 2" chairs in a 6" slab.

Sorry for the thread hijack and the soap box speech.

 

[matt_i]

So what happens when you load the perimeter of the slab where the top is in tension? A slab on grade isn't a beam where the bottom is in tension between supports and the top is in tension over the supports. It depends on uniform support from below to function.

Do not spend money on rebar in your slab in the mistaken belief that it is making your slab stronger because it simply isn't. Rebar performs the exact same function as wire mesh - it holds cracks together once they occur - it does not prevent them. The sole advantage of rebar over mesh is that it is easier to support because it is more rigid.

ACI recommends placing slab reinforcing as high as possible to keep cracks as narrow as possible. It's a moot point anyway in the real world of 4 to 6" slabs. By the time you allow for adequate cover above and below, you are in the middle third of the slab anyway, including Matt_i's example of 2" chairs in a 6" slab.

Sorry for the thread hijack and the soap box speech.

There's still lower tension in the other axis. If you drive toward the edge yes the edge will bend away ala cantilever, but perpendicular to that its still supporting tension under the tire load.

If you put it on the neutral axis then it can't do anything at all except resist shear.

Maybe two layers is best, one top third and the other lower third

I still believe the steel has some function in resisting stresses, in a directional way towards something like a post-tensioned slab. I'm confident that the rough surface of the rebar isn't able to impart nearly as much load as the sockets but there's an effect. But you don't just walk up and slide-hammer a rebar out of the concrete in which its imbedded.

From a more dynamic standpoint, I've watched highways built with wire mesh allowed to rust outside at a rest area for several months and others built with impressive amounts of green epoxy coated rebar. One was in a relatively lightly trafficked area and the other in a heavy constant truck traffic area. Im not of the belief that the designers & engineers wasted their money in the heavy truck traffic area.

I'd also offer up other civil engineering builds like stadiums, dams, bridges, etc. Some of those are chock full of thoroughly amazing metal art in the form of bent and tied rebar cages. If the designers & engineers knew they only needed a roll of wire mesh to do the same job, they would be doing it. Of course these things which I mention aren't on the same "life and limb" scale as a concrete floor slab. But the steel is there for a purpose and does strengthen, however small, is all I'm trying to represent

 

[wssix99]

There's still lower tension in the other axis. If you drive toward the edge yes the edge will bend away ala cantilever, but perpendicular to that its still supporting tension under the tire load.

Not really. Slabs do see both tension and compression almost all over the area. To understand this, you have to throw away everything you've learned about the behavior of beams and all that you've seen at stadiums, dams, bridges, etc. - that information doesn't apply because a slab is "continuously supported" by the ground. (Beams are simply supported at either end.) The forces concentrate very differently. Slabs don't need all the elaborate reinforcing because of the continuous support. (By several mechanisms, the ground ends up making up for the tensile shortcomings of concrete and provides that "strength". As Doug pointed out, the steel in thin slabs is only there as a crack width control device.)

As a vehicle drives over pavement, the area immediately under the axle bends similar to a beam under load and there is tension at the bottom of the slab and compression at the top. However, the base underneath also deflects/compresses and causes the slab to bend in the shape of a wave. In the area immediately on either side of the axle, the forces go neutral. Even further away from the axle, the pavement lifts up off of the base material very slightly - this causes compression at the bottom and tension at the top.

I just came across this reference, which details the equations behind this. (This is the first time I've seen this info outside of a textbook and freely available on the web.) Look under the "Load" section. As you have realized, there are different equations and load calculations for the corners and edges of the slab - however the Interior Loading condition usually controls for something like a simple garage slab. (Only hard-core pavement engineers and folks designing indu$trial facilities need to get into the edge and corner conditions.) https://www.pavementinteractive.org/reference-desk/design/structural-design/rigid-pavement-response/

I still believe the steel has some function in resisting stresses

Of course it does. However; since all the areas see compression and tension, taking the structural resistance of this material into account is futile and pointless. As Doug points out, the slabs we are talking about are (in the grand scheme of things) very very "thin". Even at 6", this slab is just a crepe.

Slabs with structural reinforcement do exist; however their thickness is measured in feet vs. inches and there will be reinforcement in both the top and bottom. One example of this is the pads at the very end of airport runways. (The middles are normal slabs - only the end pads that take the landing loads need this structural treatment.)

From a more dynamic standpoint, I've watched highways built with wire mesh allowed to rust outside at a rest area for several months and others built with impressive amounts of green epoxy coated rebar. One was in a relatively lightly trafficked area and the other in a heavy constant truck traffic area. Im not of the belief that the designers & engineers wasted their money in the heavy truck traffic area.

The epoxy coated stuff is really expensive and even harder to work with. It also doesn't bind as well to the concrete. It's generally only used on bridges (they are structural slabs and not the slabs-on-grade we are talking about here) or for pinning joints in heavy roads that need longevity and resistance to salt deterioration over a very long period of time.

 

[jkuro]

I'll bet the Concrete company won't guarantee the pour if it's subject to freezing. Check with your Concrete company for the amount of curing time, how many days, after the pour.

 

[bmwpowere36m3]

Slab was poured today

Spent the weekend getting it ready and it got "real" Monday afternoon when the contractor called and said we were "on" for the next day. It was miserable working Monday, heavy rain, >80% humidity in building, but it wasn't freezing.

The weather turned out great today, temps in 40-50s. 19 CY of 4000 psi mix with hot water and calcium added. Pour started 8:00 am and they finished with power-troweling and saw cuts by 2:00 pm. Slab ended up a little thicker than expected and luckily they added another yard to second truck as they had maybe a couple buckets of concrete left. Two saw cuts inside and they added some zip strips around the corners of the trench drain.

Thanks for all the advice. The guys were impressed with all the "prep" work. Given the enclosed nature of the building, by tomorrow they assure me it'll be cured to the point there is no concern for freezing.