Was given a quote for a footing that is 24″ x 8″ with two 36″ steps with finished footing measuring 41′ x 29′ on the outside.
Their math says 176′ of footing and and 13 cu yds of concrete.
My math comes out to 148′ of footing and 9 cu yds of concrete.
I am not a concrete/construction person, just going over invoices and curious if I am missing anything? I do know basic math, but am wondering if there is some special way of figuring this stuff out.?
Thanks.
Replies
you are right
41+41+25+25=132
(25' instead of 29' because if you are measuring outside of footing the width of the long footing reduces the length of the short one by 2x the footing width)
Now add to that the length of the footing over lap (24") for each side for the steps.
132+4'=136 @8" deep. 136' x 24" x 8" = 6.72 yds.
3' vertical steps:
36"-8" (depth already allowed for in standard footing) = 28", now double that depth(two steps)= 56" and multiply times that x width and length (56"x24"x24") =.691yd. call it a .7 yd.
I come up with .7 yd. + 6.72 yds.= 7.42 yds. total
ZERO WASTE
I come up with about 7.2 yards with no waste.
BUT
what you may not be telling here is something hinted in the steps.
Any time I have ever had any need to step a foundation, it was because the base was uneven over ledge so the likelyhood of exactly 8" deep all the way around is about nill and I would need to add as much as 15-20%. That gets me close to your nine yards.
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Here is my experience with having footings installed (many times) and by different subs:
The actual concrete used always comes up to more than my calculations by a significant amount. For starters when doing estimating don't subtract out for the corners. Part of this is because in my area we just excavate a ditch and fill it with concrete - no forms - except obviously there needs to be something for the steps and the steps use extra concrete too. Also, the thickness of the footings are never exactly 8" and if anything you want them to err on the thick side - obviously not on the thin side... The savings in labor costs makes up for the extra concrete costs. They spend about 4 hrs (max) installing an average footing on a fairly flat lot.
BTW - when you say steps - do you mean steps in the strip footing, or a footing for a set of steps (a step pad)? I took it to mean the former but maybe not... We wouldn't normally use a 36" step though - it would be more likely to have two 16" steps and an 8" (or similar rather than one 36" but I have no idea about the design of what you are building.
Did this footing not have any piers in the center or elsewhere? If so how does he charge for those? And you have to find out how the guy charges for the steps? He may have some kind of standard number he adds for those.
For some info on how one guy charges (the guy I use) check out his web site: http://faisonsfootings.com/ If you look at the services tab he has all the prices right there. The prices do not include the concrete which they bill be for - and give me a copy of the concrete tickets. These guys don't mess around - they show up with a tractor trailer with a excavator and a skid steer. I think they have 3 trucks. Each crew probably digs an overage of 3 footings a day. Pours take about an hour. Their laser is in constant use for the entire process.
Really though you just have to have a talk with the sub - I'm sure he will explain how he does his figuring. If he made a mistake, I'm sure he will admit it - people don't stay in business long by pulling sheet on people...
I think you are on the right track with your explanations.The contractor might be intending to dig the footing with a 10 or 12" shovel which would increase the concrete volume. Bob's next test date: 12/10/07
Thanks for the explantion, very helpful. The footing is for some poured walls of a rectangle building. The building is built into a hill side, the footing steps down 36" in the front half to stay below the frost line. The hole was excavated by someone else, and was done well. I just noticed that there was an extra $300 charge that was added for extra conctrete (3 yrds). That would make there total close to 13 cu yrds. Even when figuring extra in that seems to be a bit much?
zella, Here is my perspective on the forming and pouring of footings. Neatly dug and graded footings that are tightly formed and carefully poured should not use more than 1/2 yd. of concrete over and beyond what the calculated amount for the cu. ft. is.
A 1/2 yd of concrete is 10 lin. ft. of footings using your specs. That should be plenty to cover minor inconsistencies. Every cu. ft, that is used beyond that is simply a result of someone's decision that the cost of concrete is less than the cost of the extra concrete used.
Assume concrete is $100.00 yd delivered to you and labor is $50.00, someone made a decision that it was easier to buy 1 yd. of concrete than to spend 2 man hours in labor for every cu. yd. of concrete over and above what the actual volume need is. 2 man hours of forming can do a lot toward saving yards of concrete. I am admittedly anal about this after years of having concrete guys and concrete suppliers try to over charge me. I check the measurements against the plans, then check the finished in place pour. I have heard all the possible excuses but when it comes time to pay the bill I only pay for what was placed + a reasonable amount for truck waste (almost nothing unless you are pumping in which case 1/2 yd.) and a little spillage (maybe 1/2 yd. on a pour your size). Why should I pay someone to waste my money? I certainly don't expect a 10 percent overrun as standard , much less anything more than that. Matt's sub figures allow Matt to calc out what labor for forming is. Not what the finished job is going to cost him. Here is one trick that is done all the time.Order and bill for 12 yds. @ $200.00 a yd. placed (that is cost of concrete and placing , no forming included) Actual amount used is 8 yds. Spill 2 yds by being sloppy , send 2 yds. back to the supplier. Sub paid $100.00 yd for the concrete, makes a quick $200.00 on the returned 2 yds., plus has no real labor money in what was spilled beyond a few bucks so he makes another quick $200.00 on that. Batch plant earns $200.000 from your sub , then resells the same returned mud to the next guy for another $200.00 so they aren't going to say anything about it. Your sub just cleared $400.00 dollars pure profit and explains it away with pure horse pucky for excuses.
Do that 3 times a day when pouring footings and he clears $1200.00 a day , 5 days a week =$6000.00 a week or $300,000 a year for spinning a line of bull. Plus as he ups his monthly/yearly yardage use from the supplier his costs go down so he has no incentive to not play this game. There is a balance between the time to form and the cost of the concrete wasted, finding it is the key to using the least amount of $ to do the most. In your case I would be asking the sub to explain in detail the discrepancies and why they exist. It isn't magic, it is logic and computations.
Edited 12/23/2007 4:37 am by dovetail97128
Here is one trick that is done all the time.
Wow, some of youse guys sure make a good case for DIY <G>
Yes , sometimes it seems that way. Even my local batch plant can come up with their own version. I set a footing and stem wall for a mono pour once and I had to get a third truck to finish pouring when two should have done it. Got billed for 5 extra yards of concrete by my calculations. Called the batch plant and had the manager come out with his calculator and tape measure before I even stripped the forms. "Gee" says he "We must have shorted one of the trucks somehow." No Shid Sherlock!
They can't get your Goat if you don't tell them where it is hidden.
Yeah, when you wash your own aggregate by hand and mix your own crete, you aren't likely to make too much, are you?
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It isn't magic, it is logic and computations.
My thoughts exactly, Dovetail. This footing, as described, measures about 7 cu. yards. (I'm not sure what the op means by the 3-ft. steps. If they were sloppy in the excavation, they need to measure what they dug and/or formed and then buy the concrete needed. Like you, I dig footings carefully. I usually round up to the nearest full yard to make sure I don't run short.
Matt, I live in Durham and I form the outside of my footings for crawlspace construction. This gets the top of the footing at the exact elevation that I desire and leaves a space beside the footing for the drain tile.
One thing - he said that the excavation was done by another contractor. That in itself could be problematic.
>> I live in Durham and I form the outside of my footings for crawlspace construction. <<
If you can do footings like that for the same price as what was on that web site you need to send me an E-mail.
were the footers formed?
Footers were formed with 2 x 8s.
>> Footers were formed with 2 x 8s. <<
I think you should go out there and measure with a tape and a caluclator and see what was actually installed. Hopefully it's not backfilled yet.
"Footers were formed with 2 x 8s."There has to be more to the story than just that. You don't form a 8" footer with a 7.25" board with out some overdig or uplift. so the Q comes up - how much?Then too, I am still totally unclear on how that 36" step is formed. That can account for a yard or so of crete. Nor would i be likely to form it with 2x8s. Actually I would be extremely unlikely to form a 36" stepp all in one place, as others have mentioned.Are these footers formed exactly 24" wide with spreaders or did the footer vary in width? That could also account for another yard of crete
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I have observed footer ops done by the three major crete guys here, and all use 2x8 boards at 7.25" height to form footings specified at 8 deep.
They'll check their dig for grade, shave a little by hand if needed, add a little as needed with crushed stone, set the boards to grade with the laser at a good 8 inches up, and when all set, shovel and stomp a little dirt fill all around to shut off all the mouseholes and gaps under the boards.
Typical house job with footings done per the prints, it should take less than ten minutes to run around with a notepad and pencil, using a tape and straightedge, to gage how much crete you'll need beyond what the plan calcs have given already.
Edited 12/24/2007 10:12 am ET by Gene_Davis
different area use different method, we dirt form ours unless they are deep. minimum thickness here is 12 inches. bottom of footer 18 inches below grade. lazer grading, no has that equpiment. square point shovel string lines.if you was 1/8 wrong that 78 yards. $800
Edited 12/24/2007 10:24 am by brownbagg
3 yards extra is not alot on footing, espically if dirt formed, but on this type work you alway pay, flat rate, not T & M
I agree. I wouldn't care how much the sub told me he was buying because the contract would be awarded on a fixed basis. If this guy uses bad math, he probably wouldn't be my choice. If he's the only subcontractor in town, I see an opportunity.... Bob's next test date: 12/10/07
If 3 yds extra isn't much on a 7 yard Pour what would you consider to be an allowable extra amount on this pour? Not a footing but a slab with footings included. Measures 300' x 675' x 8' not including footings.
They can't get your Goat if you don't tell them where it is hidden.
10% about fifty yards.if you place exactly without the truck taken any back, no spillage, yield 100% it take 4995 yards or 624 truck loads, if each truck had a cubic foot of mud on its chute, thats a five gallon bucket full, that would eat up 23 yards.if its graded to nine inches istead of eight it take 5625 yards, that 630 yard more for one inch or $6300
Edited 12/23/2007 4:24 pm by brownbagg
Brownbagg, if you are the grading sub on this job, and your laser-guided equipment gets this thing 1" deep and causes me to burn $6,300 in extra crete, . . .
. . . and you didn't catch it in time . . .
Your next check from me is going to be $6,300 light.
Don't like that? You might want to consider a career move. Excavation and grading in commercial construction isn't for you.
10% of 4995 is 499.5 yds. Not 50, I know you meant that though. Thread seems to attract typos.
They can't get your Goat if you don't tell them where it is hidden.
5,000 yards.... That's around 500 trucks... At what point does it become cost effective to set up your own batch plant on site?
Long long ago when I was a field engineer on big paper mill jobs, where a kraft machine foundation alone (not the building foundation that houses it) can run over 20K yards, everything came to the site via batch truck.
In running crews to set and check line and grade for foundations, it was not uncommon for me to see over 120 truckloads a day tagged out.
But you're right. Today, economics would dictate an onsite batch plant.
When you say "batch truck" what do you mean? A regular concrete truck? And, when you say a truck was "tagged out" what does that mean? Maybe that it failed the slump test or some other test and was rejected?
Someplace way back in the cobwebs I seem to remember some church that was build such that they wanted to last for a thousand years (or some such) and it had some increatably thick foundation of x # of feet. I think the decussion where here... not sure.
Batch truck. I just should have said redi-mix truck. Just a late 60s early 70s version of the same kind of rear discharge trucks you see today.
Tagged out just means the gate control ops that the teamsters run on any big site where something's abuilding inside, employing six or seven hundred union tradesmen. A copy of the delivery ticket is left with the exit gatekeeper, the ticket gets a tag number, and it is left to office people to match it against the other copy of the ticket left with the labor foreman in charge of the pour detail.
One thing I had to do was to call out the calculated and measured yardage of any section of work I had certified "OK for placement," and the calculation needed to include the negative allowance for the volumes of the rebar and anchor bolts. Anchor bolts for a big digester tower, for example, can be 3.5" diameter, and a circular array of them might include 60 to 100 of those big boys, each L-shaped, maybe 4 feet by two feet. That, plus a bunch of tons of #8, #10, and #12 bar, can add up to a little volume.
I went out and measured the footing, see attachment. The footing was pored using 2" x 8"s, the hole was within an inch all around, they shot the top of the forms with a lazer to get an eight inch footer, minimal shovel work and packed some dirt up against the forms to seal the bottom edges. The guy that leads the framing crew loaned me his construction caculator to figure things out, what a great tool.If you figure for an exact footer at 136' x 8" x 24", you would come up with 6.72 cu. yrds. of concrete needed. Add 20%, just for some xtra volume somewhere and you come up with 8.06 cu. yrds, I even figured if you were going to do a 12" thick footing and you would only need only 10 yrds.So, so when they charge me for a footing that they say is 184(miss read the previous figure of 176) lineal feet and requires 13 yards of concrete; that's 4' more footing and 6 yrds of concrete. What's going on?Thanks.
They are trying to overcharge you . I would allow 10% at most for waste. I said earlier that this isn't magic , it is logic and computation. If you are paying by the yard for concrete have him come out and show you his math. If you had a fixed bid amount for the project pay up.
They can't get your Goat if you don't tell them where it is hidden.
He did give me a fixed bid, and I did pay up, plus some xtra.He gave me a bid, did the work and then handed me a bill. There was an additional charge for extra concrete and I paid that also. I'm not a carpenter nor a concrete person but a bit of a DIY, thought not on anything big. I'll replace a light bulb...The concrete crew also did some walls and they came out less than acceptable, out of square, not plumb.....really did a poor job. That got me to pay a bit more attention, especially when the framing crew said you have a few problems. I started to look closer at things, the footing being one of them, water proofing membrane below grade... Things just didn't add up.My walls are done and the concrete crew is gone. I have not paid the final bill and am waiting to see what the response is for the poor craftsmanship on the walls.Is it fair to withhold money from the final bill if the footing miscalculation can't be expalined. An xtra 6 yrds of concrete and 48' of footing is a pretty big miss calculation. From some responses it seems that it is fairly common practice to "pad" ones price, or as one person said "welcome to the world of construction". There is no excuse to overcharge others, just to make a bit of extra money for youreself. I guesse that is what is getting to me, the fact that I was overcharged, taken advantage of and to boot the work performed was of really poor quality. I am fortunate to have been home to watch the project and also have the brains to use a tape measure and caculator to go over a few things, most people just rely on the GC. I'm not saying that all GCs, carpentry and concrete folks are crooked, just the one that I am dealing with. What to do?Thanks, Zella.
Edited 12/27/2007 11:09 am ET by Zella
He did give me a fixed bid, and I did pay up, plus some xtra.
He gave me a bid, did the work and then handed me a bill. There was an additional charge for extra concrete and I paid that also.
This is a fixed price job and lets say he did over order on the concrete, why is he giving you a material bill on a fixed price job to begin with, and why did he give you a bill for extra concrete? With a fixed price job you can't give the HO an additional bill for extra concrete unless the HO added something extra on top of the original bid.
This whole thing doesn't make sense since it was a fixed price job. Since he was over 6 yards, where is the extra concrete, and was it added onto the extra 6 yards?
Joe Carola
Absolutely. A fixed price is done before they ever start the job and doesn't change unless the job scope changes.
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From comments here in this post I just now realize you have a batch of other threads here on this concrete issue. It could help to keep things gathered together. Are you the one with ICF going 16' high? Are you the one with the Q about the waterproofing out over the footer? Just want to get the whole picture without confusing you and somebody else here.
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So the two of you started out with a fixed bid for the footing alone. Yes you pay that , no matter what , You agreed. Now as for the extra, Have him justify it . I don't pay extras I don't understand. Can you withhold payment at this point for work that was fixed bid. Hard to do since you already paid for and signed a contract for. If you have complaints about the walls or the quality of work in general then deal with that , or , alternatively seek a lawyer out and review the whole and complete picture with him. Me , I would be talking to the lawyer about the whole issue. Fair is fair in terms of the fixed bid, he sold, you bought. But the rest of it is negotiable IMO.
They can't get your Goat if you don't tell them where it is hidden.
Whoever is doing the "charging" is either a crook, or just plain stupid. No in-between.
I sure hope you have not yet paid this yet. If you have already paid what was demanded, you will probably meet a huge wall of resistance in trying to argue for getting recompense.
Matt,
I really cannot answer that question. I simply don't know. I was site super on the pictured job.., Mud came from 3 batch plants, nearest and smallest was only a few mile away , next in size was 25 miles north and the third and largest was about the same maybe a bit more. None of these plants were very big but the larger two could deliver 10 yds per truck so that helped. We would start early as possible, use the plants from the longest distances with all their trucks for two round trips, then they would drop trucks off to handle their local business and we would keep pouring with less trucks servicing us. Most local plant arranged with the other two to cover them for small needs and also served as our clean up at the end of the day. We did the pour in 12 days so about 420 yds a day.
They can't get your Goat if you don't tell them where it is hidden.
How much do you pay for concrete? 630 yds @ 10.00 a yard = $6300.00 $10.00 A YARD? Here is is much more likely to be about $85.00 + 630 x $85.00= $53,550. I chase that inch for that money.
They can't get your Goat if you don't tell them where it is hidden.
its running around $100 a yard
Is that really 8' thick or was that a typo?
Typo, Meant 8"
They can't get your Goat if you don't tell them where it is hidden.