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Old School
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I need to use a rotary laser to shoot grade for a foundation?
First question: Do you know where your survey benchmark is located to bring in this grade elevation?
 

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Old School
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by benchmark do you mean the top of existing foundation? i am adding an addition
That could be used. But more often, your architect/engineer/drafts-person will have probably designated your existing finished floor ( FF ) as a local benchmark for elevation, and a certain point and edge angle on the existing structure for positional locating.
 

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Concrete & Masonry
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3,841 Posts
I need to use a rotary laser to shoot grade for a foundation?
Turn it on, as most newer rotary lasers are self leveling. If not, your only required to get the main unit close to level & the unit will level itself from there. As for height, normally you get the top of foundation figured out & go down from there. Crawlspace addition is usually 56" down for modular block (58 1/4" for full 8" H) for bottom of footing. Obviously, a full basement is totally dependent on the # of courses.
 

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Old School
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Your house and my house and every legally built structure in the United States is recorded in one of two national databases. These databases are available to anyone to see and refer to. The reason we have these databases is to establish the exact location, positional orientation (compass heading), and elevation of every structure. This is important for the development of future construction sites (like you are going to build) so that integrated and non-conflicting buildings can be constructed in relationship to the structures and topography in surrounding areas.

This has a lot to do with building usages, square footages, flood zones, fire districts, drainage, utility right of ways, and things like that.

So, trying to keep it simple, you are required to tell your building department what you intend to build, where it is going to sit, and how high it is in relationship to something around you. They, in turn see that your new structure gets included in the latest update of the databases.

Wouldn’t it be a bummer if you built a house, and they soon came along with a new highway (or worse, a planned reservoir) that wiped your new house right off the face of the earth? This could happen if the government doesn’t have all this good information about your proposed project.

What you need to do is employ the services of a construction firm who will pull database records, do necessary surveys, and submit all pertinent paperwork to the proper government agencies concerning your proposed project.

All this needs to be done to stay legal, and before you worry about laying out anything. And when you do all this, your plans will magically have benchmarks and trig locaters printed right on them for your use in getting your new structure in the right place.
 
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Old School
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3,634 Posts
OK. All this will do is get you in trouble, and attract some fines. But, against my better judgement, here is the most basic way this thing is used.

All this is straight addition of the total. This is the simple setup.

A more complicated setup:

If the benchmark were lower than the level sight line, then you would be doing a little more involved math. Still simple, but this is why they taught you about positives and negatives in school.

If you don't get it figured out, I may do another drawing explaining it...... if I can get past helping you get yourself in trouble with the Building Department. :wink:
 

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