Build guide

Domes, permits, and when you need an engineer

This is the question that stops most dome projects, and it deserves a straight answer rather than an encouraging one. No online calculator — this one included — can approve a structure. What a good one can do is get you to an engineer with your homework done, which is faster and cheaper than arriving with a sketch.

The rough dividing line

Requirements vary enormously by jurisdiction, and the only authority on yours is your local building department. That said, the pattern is fairly consistent:

Usually no permit — small accessory structures under a local floor-area threshold, seasonal greenhouses and hoop-style covers, temporary event structures, play domes.
Usually a permit — anything habitable, anything with plumbing or permanent electrical service, anything over the local area threshold, and often anything on a permanent foundation.
Usually an engineer as well — habitable structures in jurisdictions applying the NBCC in Canada or the CBC in California, and generally anywhere the reviewer cannot match your structure to a prescriptive code path. Domes rarely fit a prescriptive path, because the codes are written around rectangular framing.

What “stamped” actually means

A stamped drawing is one a licensed professional engineer has sealed, taking professional responsibility for it in your jurisdiction. That responsibility is the product. It is not a formatting standard you can replicate, and no amount of correct arithmetic substitutes for it.

DomeFab does not produce stamped drawings. Its structural screening is informational: factored snow and wind load combinations in the spirit of NBCC and CBC, membrane-theory member demand, and a check of that demand against Euler buckling and material capacity for each strut class. It is a useful filter for catching a design that is obviously under-built. It is not a structural analysis and is not for permit submission.

Using a generated plan set well

As input to an engineer

Engineers charge for time. Arriving with a defined geometry, a specific build system, a member schedule, and the snow and wind figures for your site removes most of the discovery work. You are asking them to check and seal a defined design rather than to invent one.

As a feasibility filter, before you spend anything

The cheapest failure is the one you find before ordering material. If a 3 m radius dome in 3/4" EMT fails its snow check for your location, you want to know that while it is still a number on a screen.

As a build guide where no permit is needed

For a seasonal greenhouse or an accessory structure under the threshold, the plan set is simply the plan set — cut lists, hub angles, fabrication templates and a bill of materials.

Before you build

Call your building department and describe what you intend to build, including footprint and intended use, before you buy material. It is a short conversation and it is the only one that is authoritative.