Metal Building Frame Selector: Span, Columns, Crane and Roof Slope
Enter the building width, whether interior columns can stand in your layout, the crane and the way the roof should drain. The metal building frame selector names the frame to ask for, from a single-span or multi-span gable to a single slope, a lean-to or a frame with a crane runway. It draws the section to scale and works out the ridge height from the roof pitch. It gives no member sizes, because every frame is designed per project.
Already know the frame? Send the width, length, eave height, crane tonnage and site country for a free layout, specification and itemized quote.
Choose Single-Span, Multi-Span, Single-Slope or Lean-To in Six Answers
Answer the six questions on the left. The result names the frame to ask for, gives the reasons and the trade-offs, and draws the section from your numbers. Change any answer and the result follows.
Estimate for planning only. The tool gives no member sizes or steel weight. Frame form, roof slope, loads and column positions are confirmed in design to the code that applies at your site.
Frame Forms the Selector Chooses Between, and When Each One Fits
The five answers the selector can give, with the conditions that lead to each. Main frames are Q355B welded H-sections, with Q235B or Q460 available, and purlins are galvanized Z or C sections.
| Frame form | Fits when | What to watch |
|---|---|---|
| Single-span gable frame | The floor must stay free of columns. Single-span frames routinely reach 60 m, and up to 100 m when engineered per project. | Span is a cost driver. A wide clear span that also carries a crane is engineered per project. |
| Multi-span gable frame | Interior columns can stand in the layout, or the width is beyond a single clear span. | Column lines have to suit racking, aisles and equipment, and they are fixed in the 3D model before steel is cut. |
| Single-slope frame | All rainwater has to go to one side, for example because of drainage or a planned extension. | The high sidewall rises with the width, and one gutter line takes the whole roof. |
| Lean-to frame | A span stands against a main frame or an existing building, or is added later as a side extension. | Whether an existing building can carry any load is checked by your local engineer. |
| Frame with crane runway | A 5 t, 10 t or 20 t overhead crane runs inside the building. | Crane tonnage, span and hook height set the frame and the eave height. |
Every form in the table is built from welded H-section portal frames, the same steel building portal frame described on our rigid frame page. Single span and multi-span are the two standard layouts. A single-slope roof or a lean-to span is a form you can ask for, and whether it suits your loads and site is confirmed in the quote.
The selector works to the ranges Xinguangzheng designs to. Single-span frames without interior columns routinely reach 60 m, wider spans up to 100 m are engineered per project, and above 100 m the selector switches to interior columns. Eave heights run 6–12 m as standard and can be raised. A quote can allow for a 5 t, 10 t or 20 t overhead crane: we supply the crane, and the crane rail system is optional.
Metal Building Roof Pitch Calculator: Ratio, Angle, Grade and Ridge Height
The calculator inside the tool converts between a pitch written as x:12, the angle in degrees and the grade in percent, then applies it to your width. The same arithmetic is set out here so you can check a drawing by hand.
| Pitch | Angle | Grade | Rise over 15 m | Ridge with 8 m eave |
|---|---|---|---|---|
| 0.5:12 | 2.39° | 4.17% | 0.62 m | 8.62 m |
| 1:12 | 4.76° | 8.33% | 1.25 m | 9.25 m |
| 2:12 | 9.46° | 16.67% | 2.50 m | 10.50 m |
| 3:12 | 14.04° | 25.00% | 3.75 m | 11.75 m |
| 4:12 | 18.43° | 33.33% | 5.00 m | 13.00 m |
- Angle = arctan(pitch ÷ 12). A 1:12 pitch is 4.76°.
- Grade = pitch ÷ 12 × 100. A 1:12 pitch is 8.33%.
- Gable ridge height = eave height + half the width × pitch ÷ 12.
- Single-slope high side = low eave height + the full width × pitch ÷ 12.
Pitch in a steel building quote is usually written as rise in 12, so 1:12 means the roof climbs one unit for every twelve units across. The table works through a 30 m wide gable with an 8 m eave: half the width is 15 m, so each step in pitch adds the rise shown to the ridge.
A single slope climbs over the full width rather than half of it, which is why the same pitch gives a single-slope building twice the rise of a gable of the same width. The final roof slope is set in design together with the roof sheet, the drainage and the loads at your site, so treat these numbers as planning values.
From a Frame Choice to a Frame Design and a Quote
The frame form is one input to the quote. These are the others that go with it, and what comes back.
- Send the frame form, width × length × eave height, crane tonnage and hook height, and the site country and city.
- Loads, spans and coatings are engineered to the code that applies at your site, commonly AISC 360, EN 1993, AS 4100, AS/NZS 1170 or GB 50017.
- You receive a free layout, specification and itemized quote for projects from 3,000 m².
- The building is modeled in Tekla 3D, and steel is cut only after you approve the model.
The selector narrows the frame form; the design fixes it. Our pre engineered metal building design guide explains how site loads, the design code and the 3D model come together before fabrication. Projects under 3,000 m², or projects that need one supplier to build the foundation and erect the steel on site under a turnkey contract, are not a fit for this kit supply.
Frame Selector Questions: Spans, Slopes, Cranes and Sizes
What does the metal building frame selector tell me?
It names the frame form to ask for (single-span gable, multi-span gable, single slope, lean-to, or a frame with a crane runway) from your width, columns, crane, drainage, position and expansion plans. It also draws the section to scale and gives the ridge or high-side height for your pitch. The frame itself is confirmed in design.
Does the selector give member sizes or steel weight?
No. Member sizes and steel weight depend on the loads and code at your site, so they come from the frame design behind your quote. The selector stops at the frame form and the main heights.
How wide can a column-free steel frame span?
Single-span frames without interior columns routinely reach 60 m. Wider spans up to 100 m are engineered per project, and above that the layout uses interior columns.
When does a single slope or a lean-to make sense?
A single slope suits a roof that has to drain to one side. A lean-to suits a span that stands against a main frame or an existing building, or a side extension added later. With either, the high side rises with the width, so check the height the tool gives.
How do I convert a 1:12 roof pitch to degrees and percent?
A 1:12 pitch is 4.76° and a 8.33% grade. The angle is arctan(pitch ÷ 12) and the grade is pitch ÷ 12 × 100. The roof pitch calculator in the tool converts in all three directions.
Can a crane be added to the building later?
Say so in your inquiry. Crane tonnage, span and hook height set the frame and the eave height, so they are best fixed at design stage. A quote can allow for a 5 t, 10 t or 20 t overhead crane.
What happens after I send my details?
You receive a free, no-obligation quote with a layout, a specification and a full cost breakdown. Xinguangzheng models the building in Tekla 3D and issues shop drawings, and the 3D model goes to you for approval before any steel is cut. Projects start from 3,000 m².
Send Your Frame Choice for a Layout and Itemized Quote
Copy the result from the frame selector into your email or WhatsApp, or simply send the width × length × eave height, the crane tonnage and the site country. We return a free layout, specification and itemized quote, and the frame form, slope and loads are confirmed in design.
End elevation of a single-span rigid frame with an open floor and no interior columns
