Starting point for building height measurement

[Otis]

What do you use as the starting point for building height? In DeOtis we use "finished grade" which begs for artifical fill. Do you use original grade? Something else? What is "best" in your opinion? How is whatever you use determined (e.g., how do you know what original grade was?) Complaining minds want to know.

[RichmondJake]

This is a can or worms.

My current jurisdiction measures from final finished grade. In previous jurisdictions, it was from original grade to discourage excessive grading.

What's best? If you have good baseline data, original grade.

[Chet]

I agree with finished grade, but poor "site balance" does not equal an approval of the finished grade.

[The One]

We have to go by the most restrictive of either the Zoning Regulations or current building code, 2003 IBC/IRC. The old 97 UBC measured from a point setback from the home and averaged. It also measured to the midpoint of the eve and peak of the roof. Some zoning codes measure to the peak of the roof, some have other measures....so RJ's right about can of worms. Did I just admit RJ's right about something....

Take the Zoning code definition of height and compare it to the current building code for the jurisdicition you're in.....then pick the most restrictive.....that's how you measure height. For a single home built on an infill lot, measure from the original grade as determined from the average of four points at 10 feet from property lines. This will avoid most swales or drainage features and get you a decent start point from surrounding property (unless you are in the mountains) If this is a brand new subdivision, measure from finished grade using either the zoning code or building code, whichever is more restrictive.

[Otis]

Unfortunately the Oregon version of the building code uses finished grade as does our zoning ordinance. My council seems to want "existing grade" but there are some questions about how to determine that. Boulder County Colorado requires a pre-construction survey to determine the "existing grade:" http://www.bouldercounty.org/lu/info...ade_verify.pdf
and then a post-construction survey to verify building height:
http://www.bouldercounty.org/lu/info...vey_verify.pdf
I've considered going this route, but it would add thousands of dollars to housing costs and probably inject some delay into the process. It would have the advantage of providing full employment for surveyors, however.

[The One]

Originally posted by Otis

Unfortunately the Oregon version of the building code uses finished grade as does our zoning ordinance. My council seems to want "existing grade" but there are some questions about how to determine that. Boulder County Colorado requires a pre-construction survey to determine the "existing grade:" http://www.bouldercounty.org/lu/info...ade_verify.pdf
and then a post-construction survey to verify building height:
http://www.bouldercounty.org/lu/info...vey_verify.pdf
I've considered going this route, but it would add thousands of dollars to housing costs and probably inject some delay into the process. It would have the advantage of providing full employment for surveyors, however.

Were "they" required to get a grading/fill permit prior to adding fill to the property? If so, is there a plan that might show elevations or maybe a cut/fill map? If not, you could just declare the low point in the adjacent ROW to be natural pre-exisitng grade.

[Otis]

The problem that has lead to the pressure to amend the ordinance was a lot that sloped steeply down away from the road (E-W) and steeply down along the road (N-S). We do require grading permits but at this point do not have much in the way of standards for them (filling a wetland? no? OK, go ahead and grade.) But that's an idea: address the grading issue in the grading permit.

[southsideamy]

I just read an interesting ordinance that measured building height from the elevation of the centerline of the adjacent road. Very auto-oriented (why not from the centerline of the sidewalk??), but brings the idea of perspective into the discussion. Also, I'm not sure I would have that data in my fair city.

[mike gurnee]

I have seen the road centerline basis--regarding sign heights.

[The One]

Originally posted by southsideamy

I just read an interesting ordinance that measured building height from the elevation of the centerline of the adjacent road. Very auto-oriented (why not from the centerline of the sidewalk??), but brings the idea of perspective into the discussion. Also, I'm not sure I would have that data in my fair city.

This could get weird if the road has an inverted cross section for antiquated drainage control

[southsideamy]

Otis: To answer your original question, our zoning ordinance uses finished grade to determine building height.

The finished grade is the controlled by our subdivision and development regulations which requires permits for any cut or fill. Our engineers review the grades of new subdivisions and commercial lots very closely -- we always want to make sure that someone isn't filling in a property in a way that either causes a drainage problem on another property or allows a finished floor elevation to be dramatically different (or, should I say, noticably different) from a neighboring property. We require three surveys (with elevations) during a redevelopment - including a final survery after landscaping is complete. This really does discourage raising grade to exceed required building heights.

This probably isn't the best method, but it's the one we use. I would consider it dumb luck that we haven't had issues.

[calgaryplanner]

When I worked in Halifax - height depended on the bylaw. There were 22 land use bylaws in Halifax - it all depended where you were! In the Halifax Mainland Bylaw it was centre line of the roadway if memory serves me.

Here in calgary we required geodetic height elevations at the property line corners and then take the average between each side.

I've attached the diagram - hope this helps.