Need Concrete Knowledge

[Wayne County Hose]

I have decided to stick build my new home. Unfortunately, the weather here in the northeast is typical January. My old basement was 6'. I want to add 18" of concrete to the top of the existing foundation. I don't want to go any higher as the house will stick up out of the ground way too much. 18" is really too much. Anyway, I am concerned about having concrete poured in sub-freezing temps. I am told that the additive used to keep it from freezing weakens it. The existing foundation is 4500lb. concrete. I know it would probably be okay to pour it anyway, but I would rather have both pours the same strength. Does anyone out there have concrete knowledge on this? Pun intended by the way. Thanks for any help, Andy.

 

[tommu56]

What about 3 - 4 courses of block added to existing foundation?

tom

 

[SpringHollow]

Your concrete supplier can make the concrete to the strength you need as well as having the correct freeze protection. They have to do this for commercial construction all of the time, often with higher rated concrete than what you need.

Ken

 

[Egon]

It all depends on the outside temperature. High early concrete is only good for limited freezing. Hoarding and heat may be needed.

 

[EddieWalker]

I'd go with block. Drill holes in the top of the existing wall for half inch rebar and epoxy them in place. Morter the block into place and cross the tops of the second to top row of blocks with rebar that you tie together with the vertical rebar in your wall. Fill the cavities with concrete.

Trying to pour a concrete wall on top of an existing wall is more complicated then I'd be willing to try. I would also be very hesitant about hiring it out as it's not a common job and you'll be lucky to find somebody who actually knowos what they are doing. If it's wrong, your entire house will move.

Eddie

 

[rimshot]

There is no question about it. Pour concrete if you only if you absolutely have to in sub freezing temps but you will get 1/2 the workmanship and it will cost you twice as much. Once poured cover it all as best you can even if it means using styrofoam, tent it and keep heat on it until weather returns to above freezing as long as you can otherwise. make sure you add not more than a 2% chloride to your batch as it will speed up hydration of concrete. If you can lay blocks as opposed to forming/pouring that might not be as bad. Make double sure you don't pour over any frozen soil. If you use mortar see to it you use a frost preventer like a liquid additive to water and use hot water and sand can be heated as well. Remember also there is a downside to using chloride as you know what happens when chloride and any steel reinforcing come together.

rim

 

[crbr]

I have decided to stick build my new home. Unfortunately, the weather here in the northeast is typical January. My old basement was 6'. I want to add 18" of concrete to the top of the existing foundation. I don't want to go any higher as the house will stick up out of the ground way too much. 18" is really too much. Anyway, I am concerned about having concrete poured in sub-freezing temps. I am told that the additive used to keep it from freezing weakens it. The existing foundation is 4500lb. concrete. I know it would probably be okay to pour it anyway, but I would rather have both pours the same strength. Does anyone out there have concrete knowledge on this? Pun intended by the way. Thanks for any help, Andy.

Wait for better temps.

 

[Egon]

[QUOTEWait for better temps.][/QUOTE]

Now that is good advice.


Long small pour sections do not generate much heat when curing and are difficult to hoard.

 

[Wayne County Hose]

Waiting for better temps is not an option. I have spoken to some builders and they tell me do not use heaters and enclose. Heaters remove oxygen from the air and the concrete won't cure properly. I'm also told that pouring on top is okay. The contractor is boring holes into the existing foundation and adding rebar into those holes. He is also placing the forms along the existing foundation.

Eddie, I like your idea. Is this something you have done? I didn't want to go with block, but the job is not started yet.

The contractor is very respected in the area. He poured the original foundation 15 years ago. The engineer that came to inspect it after our house fire told me that whoever did our foundation did an exceptional job, and he was very adamant about it. So, I do trust that if he pours it, all will be okay. My main concern is pouring in cold temps.

Ken, that's kind of what I'm hearing. I had a customer in today that used to work for a cement company. He told me that they don't use calcium anymore. He said they use something else that also speeds the curing time.

Thanks for all your inputs, Andy.

 

[Egon]

I'm afraid your contractor is not familiar with pouring concrete in cold weather. Maybe cool weather but serious cold is a different animal. Adding heat is the only way to go. There are different ways to do this.

 

[CurlyDave]

Waiting for better temps is not an option.

I don't see why you are using concrete at all.

Unless you are intending to raise the grade level around the house, your existing foundation is high enough to prevent termite problems.

I would build an 18" pony wall, which can be done in any weather.

Get an engineer to look at the plans. Pony walls built without proper shear paneling are dangerous, but if you use something like 1/2" plywood on both sides it will be fine.

 

[Erik_in_Hoyt]

if you're avoiding using block for the addition because of the look, you can always come back when it's warmer and give it and the exposed part of the original foundation a surface coat of dryvit or something similar so it all looks seamless.

Eddie is more of an expert at this sort of thing than me, but what he describes sounds plenty structural based on my limited experience.

properly filled and reinforced block walls are plenty strong, otherwide they wouldn't be so common in commercial applications.

 

[Wayne County Hose]

Curly Dave- not worried about that. Existing foundation gave me a 6' basement. Was like that when I bought it. I need more height in the basement. I really need 10', but that's not practical, I'll settle for 7' 6".

Erik- Eddie had a great post before. I'm waiting for him to expand on it. I'm not worried about the look, I'll probably put fieldstone up to the siding level in the fall anyway. I'm planning a hydraulic fieldstone cutter. I have the plans all figured out and will make it in the spring.

Egon, do you know something more here? I need to know if this is an issue and I need to know exactly why. If I really need to wait until above 32 degrees to pour, I will but I need "concrete" reasons. Eddie's idea is sounding more appealing. I will be patient and hope he expands on his last post.

 

[EddieWalker]

Waiting for better temps is not an option.

Eddie, I like your idea. Is this something you have done? I didn't want to go with block, but the job is not started yet.

The contractor is very respected in the area. He poured the original foundation 15 years ago.

Yes, I have some experience with block walls and building with them. No, I don't have any experience or knowledge of working with cement in freezing temps. I also don't have any experience with basements or building up from a wall that tall. What I've done is build additions and remodel existing homes.

I didn't tell you how far to space the rebar because I don't know for sure in your situation. I also might have mispoke when I recomended half inch rebar. that might change depending on height and spacing.

There are several issues with what you are doing. A solid concrete wall could very well be the way to go if you have a contractor who knows what he's doing. The key will be in the rebar and how it's done. If he uses an epoxy to set the rebar, that's a very good sign. If he drills some holes and sticks them in the hole and does nothing else, then I'd be worried.

Since your contractor has been doing this for more then 15 years, I'd tend to listen to him. If he didn't know what he was doing, he wouldn't have been able to have lasted that long. It might be worth your piece of mind to consult a local engineer who's familiar with your area and weather conditions, but otherwise, I'd tend to listen to the contractor.

Eddie

 

[Wayne County Hose]

Good advice Eddie, as always. I'm going to put this job on hold until I speak to an engineer. Thanks again, Andy.

 

[Egon]

One can pour concrete when there are a few degrees of frost and its covered over as the curing process generates heat. The greater the volume - mass of concrete the more heat is produced and lower outside temperatures can be tolerated.

In your case the concrete mass is well distributed and will not contribute much to overall heat. Hoarding and outside heat will be required for a proper pour.

On construction sites heaters are usually of the Herman nelson type or propane heaters depending on whats available and costs less to use. They usually blow hot air into the hoarding.

The lack of oxygen is a new one that I have not heard about. In fact it sounds kinda funny if one looks at slab pours that are bottom sealed by plastic and covered by plastic on hot days to prevent the evaporation of water from the mix which results in spalling down the line.

Check out the Portland Cement Association guidelines for proper information. You could spend some time on their site as it goes from a to z on concrete.

 

[MrJimi]

Andy, just call a couple of concrete companys in your area, they will know all you need
Jim

 

[philbuilt]

I agree with CurlyDave. If your only raising the basement height and not the outside grade use wood. Then the exposed area you can ad the Field stone to clad the outside. This is an opportune time to also run the basement framing to to floor for a finished space.
Phil

 

[EddieWalker]

I think Dave and Phil have the best idea. Tying a pony wall into your interior wall framing would make a very strong support that would easily support the load of your home. The studs running down the interior of the wall would give you the support and shear strength that you need to hold the pony wall in position. Drill and bolt the sill plate into position and use 2x6's on 16in centers with a double top plate.

No concrete and you're already a step closer to finishing off your interior walls!!!!

Eddie

 

[CamshaftLF]

Andy the curring time for concrete is 28 days in normal temp, it can be poured with the accelerator aided and then covered with insulating blanks for the 28 days or till temps rise. And accelerator don't keep crete from FREEZING all it doe's is speed up the set time. crete will not freeze the first or second day because its making its own heat. But it still needs to be covered. Ive poured sections of my drive way when the nights where freezing I put the insul blanks over it and put a 100 watt flood lite under the blank to keep it from freezing . but that was a small area. The 28 day cure time hardly anybody sticks to it because of the supply and demand or died lines to meat. And yes I've delivered concrete for 14yrs in central pa mostly around the PSU campus in S C Pa. Hope this helps u just needed to clear up the additive story so if u talk to a crete supplier and he tells u it will keep it from freezing he's blowing smoke period. It's the slow time of the yr and they just want to sell their product.!!!!!!!!! Theirs good info given to u here its up to u to decide.

Good Luck!!!