These packages are calculated to IBC 2018 and ASCE 7-14, Risk Category I for open structures. Capacity figures on this page are bearing capacities at the support — compression perpendicular to grain at 625 psi times the member’s area — not bending capacities. Bending is checked separately in the sealed package.

Which timber structures have a PE-stamped engineering package?

Nine drawing and calculation packages, holding 26 calculation packets in total, cover the pergola, the pavilion, the gazebo, four cabana sizes, the trellis and the arbor. Each one below has its own page with the member sizes and loads printed in its package.

Carports, timber boat houses and interior or exterior beam work are engineered per project rather than from a package, so they are not in this list.

What design loads apply across the structures?

Every stamped package in this set shares one starting point. Ground snow is run at both 30 psf and 50 psf, which pair with 23 psf and 38 psf on the roof. Dead load is 15 psf, live load 20 psf. Wind is 115 mph as an ultimate design speed in Exposure B for an open structure, which is an input to the calculation and not a storm rating. Soil bearing is assumed at 1,500 psf.

How do the 30 psf and 50 psf snow packages pair?

Each calculation cover pairs a ground snow value with a roof snow value. Ground 30 psf pairs with roof 23 psf. Ground 50 psf pairs with roof 38 psf. Two options are not a mapped snow-zone certificate. The package issued for your county states which pair was used.

How much load do the posts and beams carry in the bearing tables?

A nominal 10 in. by 10 in. post is tabulated at 62,500 lb bearing capacity across these packages. Beam capacities are printed per member on each structure page, because they change with span and with the snow option.

How much load do the posts and beams carry in the bearing tables?

What foundation and soil assumption is used?

Footings are sized against an assumed soil bearing pressure of 1,500 psf. A geotechnical report is requested. Where an owner declines one, the package records that the assumption stands at the owner’s risk. One shared post footing and anchor detail is checked against a single bounding uplift demand of 3,299 lb, reused across the packages rather than recalculated per product.

Who designs the structures, and who seals the drawings?

Shane Watson, PE (Utah #5206456-2202) is our structural engineer and leads the design of our timber systems. He holds professional engineer licenses in 21 states, listed on this page. Leading the design is not the same as sealing every permit set himself.

For a building permit, sealed drawings are issued only by an engineer licensed where the plans are filed: by Watson in the states where he is licensed, and by a coordinated engineer licensed in that state where he is not. A seal applies to one structure on one site and does not transfer.

Western Timber Frame has completed jobs in all 50 states. Completing a job in a state is not a claim that Watson is licensed there, and a Utah seal is not valid for a permit elsewhere. Zoning, the permit application, foundations and site work stay with the owner or contractor unless your contract says otherwise. We do not guarantee permit approval.

Which states is the engineer licensed in?

Shane Watson, PE is individually licensed in Alaska, Arizona, Colorado, Connecticut, Florida, Hawaii, Indiana, Iowa, Kentucky, Michigan, Minnesota, Montana, Nevada, New Mexico, New York, Pennsylvania, Texas, Utah, Washington, Wisconsin and Wyoming. The license number we publish is Utah #5206456-2202. Where a state requires a license number on the sealed drawings, we pull it for that state, and where a project calls for it we work with engineers licensed in that state. Your package is sealed by an engineer licensed where the structure is being built, and those sealed drawings are what a permit office reviews.

How is bearing capacity calculated across every structure?

One method, every package: 625 psi times the member’s bearing area. That 625 psi is the published compression-perpendicular-to-grain design value for Douglas Fir-Larch, and every member in these packages is Douglas Fir #1 or better. Sixty-two of the sixty-two bearing capacities published across our nine structures reproduce from it exactly.

Bearing capacity by member size, at 625 psi
Member	Bearing area	Capacity
4 in. by 8 in.	32 sq in.	20,000 lb
4 in. by 10 in.	40 sq in.	25,000 lb
4 in. by 12 in.	48 sq in.	30,000 lb
4 in. by 14 in.	56 sq in.	35,000 lb
4 in. by 16 in.	64 sq in.	40,000 lb
6 in. by 16 in.	96 sq in.	60,000 lb
6 in. by 20 in.	120 sq in.	75,000 lb
10 in. by 10 in.	100 sq in.	62,500 lb

The 625 psi figure is the published compression-perpendicular-to-grain design value for Douglas Fir-Larch in the American Wood Council’s National Design Specification for Wood Construction (NDS) Supplement, Table 4A. The snow conversion follows the flat-roof snow equation in ASCE 7-14 Chapter 7. Both are named here so the figures above can be checked against their source rather than taken on trust.

Read every bearing percentage on this page as crushing at the bearing surface only. It is not a member’s axial, buckling, bending, shear, deflection or connection utilization, and any of those can govern at a far higher percentage. Those checks are separate calculations in the sealed package.

How does ground snow become roof snow in these packages?

Every package runs two ground snow cases and converts each to a roof snow load. The conversion is identical across all nine structures.

Ground snow to roof snow, all packages
Ground snow	Roof snow	Ratio
30 psf	23 psf	0.767
50 psf	38 psf	0.760

Both ratios sit within one percent of each other, which is what a single set of exposure, thermal and importance factors produces. A site outside those two ground snow cases gets its own sealed calculation rather than an interpolation from this table.

What wind load does the package calculate at each load point?

Wind enters every package at 115 mph ultimate in Exposure B — the figure the calculation starts from, not a survival rating. Each package resolves its governing wind case to four load points.

Governing wind case by structure
Structure	Plan modeled	Total	At each load point
Trellis	18 ft by 3 ft	457 lb	114.25 lb
Gazebo	14 ft by 14 ft	2,493 lb	623.25 lb
Cabana 16 by 16	16 ft by 16 ft	1,484 lb	370.90 lb
Cabana 20 by 20	20 ft by 20 ft	2,202 lb	550.40 lb
Cabana 16 by 20	16 ft by 20 ft	2,967 lb	741.79 lb
Pergola	16 ft by 20 ft	3,387 lb	846.78 lb
Cabana 20 by 30	20 ft by 30 ft	4,451 lb	1,112.69 lb
Pavilion	24 ft by 23 ft	5,059 lb	1,264.75 lb

Each packet prints both the total and the per-load-point figure. On five of the eight the per-point figure does not equal the printed total divided by four — 370.90 lb times four is 1,483.60 lb against a printed 1,484 lb, for example — because the packet rounds the total for display and computes the per-point figure from the unrounded value. We publish both as printed. Read them as calculation results for the plan each package models, not as ratings for a structure of any other size. The arbor package resolves its main wind force to zero because that structure has no gable length and no roof slope.

Does this page work as permit documents by itself?

No. A permit office needs the sealed package prepared for your building and your county. Packages are site-specific, single-use, and non-transferable, and they are void without a proper engineer’s seal. Bigger spans, a different exposure, higher snow or wind, or soil that does not match the assumption get new site-specific calculations rather than a copy of this summary. Western Timber Frame builds each structure to order, so member sizes can change before any timber is cut.

What if my site needs more snow or wind than the standard package?

The standard packages are stamped for 30 psf to 50 psf ground snow and a 115 mph ultimate design wind speed. A site that needs more capacity is normally handled with larger members, closer framing, or both, together with site-specific engineering sealed by a professional engineer licensed where the structure is being built. We fabricate to sealed drawings; we do not perform structural design through this website.

Do you handle the permitting for us?

We help you through it. We do not file the permit application or pay the permit fee. Who is allowed to file depends on your city. Most places let the property owner, a licensed contractor, or an authorized agent apply. Here is what we do: We design your structure to the setback, height and code rules we can confirm for your address. A setback is how far a structure has to sit from your property line. When your project scope includes them, we prepare stamped structural drawings for your site. Stamped means a licensed engineer has signed them. They are drawn for your project, not copied from a generic plan. We prepare the structure documents your building department asks us for. We tell you what to submit, and in what order, so you are not guessing. If the building department sends back comments about our structure, we answer them and revise the drawings. You or your contractor file the application and pay the city’s fee. Some things stay on your side because only you can supply them. Those can include a property survey, a plot plan, HOA approval, contractor registration, and scheduling inspections. Your city decides which of these it wants. A lot of builders will not talk about permits at all. We would rather tell you plainly what is required, what we handle, and what is yours to do, before you buy instead of after. Western Timber Frame manufactures the timbers at its own Utah plant, so the company that draws a structure also builds it.

Shane Watson, PE (Utah #5206456-2202) seals our structural engineering packages and holds professional engineer licenses in 21 states. Sealed drawings for a permit are issued by an engineer licensed in the project state — Watson where he is licensed, or a coordinated in-state engineer where he is not. Figures on this page are summarized from the stamped engineering package (Project 5C 25-022, calc job SSE WTF-026-03) and are calculated to IBC 2018 and ASCE 7-14. The sealed PDF prepared for your address controls.

Ready to talk through your project?

Whether you want to permit, hold off for now, or you’re still deciding, we’ll walk you through what’s typical for your city and design a structure that’s built — and documented — to the same standard either way. Start with a free design consultation.

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