I’m trying to estimate some concrete construction using Means. The formwork for the footings is based up “square foot contact area.” I’m not sure what it means.
I think it means the area of the form that’s in contact with the concrete, on both sides of the footing. Example: if I have a 10′ length of footing that is 12″ tall, that would be 20 lineal feet x 2′ of vertical formwork (1′ each side) = 40 square foot of contact area.
Is that the way is calculated? If so, at $3.91 per SCFA, that’s gonna add up really fast.
Replies
Well you've got the SFCA concept right, but in your example a 10' long footing 12" high formed two sides would have 20 SFCA. You're right with the concept, you just doubled the 10' twice. Keep doing that and your estimate will be way out of whack...lol.
Bear in mind that for a 12" tall footing, the concrete sub will probably use 2x12's (which are actually 11 1/4"), and hang them 3/4" above the footing bottom. Given the current cost of 2x12's around here at about $1,25/LF, your material costs will be around $1.50/LF (assuming $0.25 for stakes, duplex nails, cross bracing, etc). If you're looking to save some money, frame the floor or roof system in 2x12's and hopefully you can re-use some of the form material in the floor- you might be able to reuse 75% or so of your formwork that way.. Just don't let them oil the forms, since you'll never get the form oil smell out of the house.
That, my friend, is building green- conserving resources.....
Bob
P.S.- Don't put too much faith in Means numbers- they're notoriously inaccurate- especially for residential construction.
Would you suggest a more accurate one?....
Or are they all pretty much the same? regards
In general, cost books are pretty bad for residential. They seem to be better (though still not great), because a large amount of commercial work is done using either union labor or prevailing wage rates. This makes it easier for the publishers to get semi-accurate data for various areas of the country on commercial work.
By comparison, in one local area you'll have carpenters getting paid from $10/hour to $25/hour, and companies with overhead markups ranging from 10% ( for the clueless "I can be a contractor- I built a doghouse once" types) to 40%. This makes it tough to provide accurate cost data that will be relevant to your company.
The book I most often recommend, especially for remodeling, is Craftsman's National Insurance Repair and Renovation Cost Book. The productivity rates are the best I've found for remodeling-quantity work, and they use a pretty decent labor rate as their basis for determining labor costs.
In general, I recommend only using cost books for determining productivity rates for tasks you don't have your own data, and even with that, I suggest comparing the book's productivity rates for a item you do have data on, to see if your crews tend to work faster or slower than the book's crews. Then apply your actual hourly costs/rates to the adjusted productivity rates.
Relying on the cost books to generate your pricing is like rolling the dice in Vegas- you'll win some, and you'll lose some- you've just got to hope that you win more than you lose.
Bob
Thanks Bob, I'll check out Craftsman....
I use Means sometimes but it's always been for
productivity values...
Bob - My Dad started doing the form recycle thing back in the 40's, talked about it for years. I've been told that current inspectors will not allow it. Some of the codes mandate "new" wood.
Have you ever had a problem like that?
Don
Never saw that happen with forms that were used once with the grade stamps still visible. I could see it being a problem if you oiled the forms, used them 4 or 5 times, and banged the daylights out of them taking the forms off, but not one use. I guess 2x4's used as wall bracing on the first floor can't be used for wall plates in the second floor framing?
Of course, when in doubt, ask the inspector first....
Bob