Double Garage Steel?

[ab122]

I've a 203x133UB25 beam ready to be installed across a double garage opening, it will have a wall plate fitted and hold one end of the timbers of a flat roof, may also hold the double garage door later.

 

SE stated the above on a quick phone chat, but never came back to me with calcs or info and or confirmation and is ignoring my calls. No BCO involved

 

2 questions

 

1. Is it undersized? Ive been doing some reading and seen people are using 203 x 203 x 46 or 60 in these cases

2. What size padstone is best for either the 233 UB or the 203 from q1?

 

Dimensions attached

 

Thanks guys!

[Temp]

I'm not an SE so thought I would ask ChatGPT to suggest a beam for a 4.9 meter span supporting a timber roof and garage door. It replied..

 

Quote

 

To suggest a Universal Beam (UB) for a 4.9m span supporting a flat timber roof and a garage door, we need to consider a few key factors. Since this is a residential garage, I’ll base the suggestion on common load assumptions and provide a preliminary beam size. For exact sizing, consult a structural engineer, especially for compliance with local building codes.

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🧱 Assumptions

Span: 4.9 meters (clear span)

Support: Simple (pinned each end)

Roof: Flat timber (assume light domestic load: ~0.75–1.0 kN/m² including snow/loadings)

Garage Door: Assume motorised sectional door (modest point load at lintel level)

Load Type: Uniform load from roof, possible point load or concentrated line load from garage door

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📐 Recommended Preliminary Universal Beam

A good starting point would be:

✅ 203 x 102 x 23 UB

Depth: 203 mm

Width: 102 mm

Weight: 23 kg/m

Section Modulus (Zx): ~95 x10³ mm³

Moment capacity: ~35 kNm (depending on grade, usually S275 or S355 steel)

This size generally handles:

Moderate uniformly distributed loads up to ~10–12 kN total across the span

Small to moderate point loads

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📌 Notes

If the garage door exerts significant point loads (e.g., from a heavy header or track system), a slightly larger beam such as 254 x 102 x 25 UB might be more suitable.

Ensure adequate end bearings (minimum 100mm but ideally 150mm).

Check deflection limits: typically span/360 for roofs (so max deflection = ~13.6mm).

Use padstones or suitable supports under the beam ends.

For aesthetic or headroom concerns, you might consider a Parallel Flange Channel (PFC) or flitch beam instead, depending on layout.

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📄 Summary

Span    Load    Suggested UB

4.9m    Flat timber roof + garage door    203 x 102 x 23 UB (preliminary)

Let me know if you have:

The exact roof construction details

The garage door type and weight

Any height or clearance constraints

With those, I can refine the beam selection further.

 

 

I expect this assumes the wall plate is going on top of the beam so if it were bolted to the sheer web instead it might give a different answer?

 

As for padstones.. You don't have much area according to your drawing so I would use all of it eg 33cm and 21cm long x 103 if it's a single brick. I'd make them two brick courses high.

 

..but remember I'm not an SE.  Let's see what others think.