On extremely cut-up foundations, we'll often have a surveyor "pin" the corners for us one the footings are poured.

Your layout isn't really that complicated and can be laid out easily & accurately with a plain ole' steel tape. A nylon coated steel 100' tape won't stretch like a fiberglass will in long lengths. The tape can be more accurate by using the 12" mark for your starting point, as the end of the tape is often bulky loose, and an add to more discrepincies.

As for the 90* corners, they're easy when you use the Pythagorean theorem, A squared + B squared = C squared. A construction calc with feet/inches is extremely helpful for this. I typically run these numbers in the office beforehand and just note them on the print to save time in the field.

 

You can certainly buy a better quality transit, or you can rent one from a U-rent place. An adequate transit for layout work would be accurate to within a few seconds of arc. A little perspective on accuracy. A 1 degree error is 1.7 feet per hundred, obviously unacceptable. A one minute error (1/60 of a degree) is an error of .03 feet per hundred, which may be acceptable for building layout, but is pretty poor. A 10 second error (1/360 degree) is an error of .005 feet per hundred, well within tolerance.

You can get similar results if you use a non-stretch calibrated tape using the 3-4-5 right triangle principle. You have to keep the tape level, which is a real pain over distance, hence I prefer using a 10 second or better instrument.

 

Please share your tips for precision layout - preferably on a budget but, if necessary,

Ayuh,.... Batter boards, string lines, 'n careful meassurements,...

 

There's also the Groma used for 1,000's of years and never fails.

Some people will tell you that plumb lines don't work in windy conditions, but if you let the plumb bob hang in a bucket with some oil in, it will work perfectly.

 

There's also the Groma used for 1,000's of years and never fails.
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Some people will tell you that plumb lines don't work in windy conditions, but if you let the plumb bob hang in a bucket with some oil in, it will work perfectly.

Cool! Do you also use a chorobates?

All joking aside, I honestly do use a water level quite often.

 

Don't forget after you have turned your angles (no matter the method you choose to use) double check all your squares and rectangles by pulling a steel tape diagonally from corner to corner. The opposite cross measurements must read exactly the same.

 

I went to both rental places in town today to see what they had. Both had sub-300-dollar optical levels - that was it. And they want 50 a day to rent them. Amazon has a David White theodolite that goes to 5 seconds for 861 dollars. If I bought one, I could probably sell it for 500 or 600 on eBay after the house is built so, to me, renting junk for 50 a day is just not an option. But, I don't want to spend the money for the David White either.

I am leaning toward the 1000s of years old Pythagorean theory method. Batter boards are a real problem here; the soil is so rocky that we can't pound more than a few inches in most places. I even bought the Rousseau batter board system with metal form stakes to try to get around it. As I pound them in, the metal form stakes turn and twist around the rocks - and many of them still won't go far enough into the ground to be stable.

I just realized, though, that even though I can't them to go in straight enough to use with the Rousseau units, I could use the metal form stakes and get a wooden board level across them. I'll put in some stakes as best I can before the excavator comes so I can get as close as possible to recreating a corner pin as a starting point when we actually start the layout for the forms. I have a bunch of 6 inch nails that I can use to mark points that I should be able to get into the ground accurately.

It's probably no surprise for anyone who has taken on something like this; I took off this week to be here when the excavator came - originally scheduled for Wednesday. Now he isn't coming until, hopefully, Friday. Possibly Saturday.