How much weight can a garage roof hold?

Question

I'd rather not start the year off by falling through a roof, so Is it safe to walk on a garage roof without damaging it? It is a flat felt roof and I need to get up there for a quick job, but I’m worried about it sagging or giving way under my weight.

Chris · Answer

Generally a flat roof is safe to walk on unless it is noticeably rotton or soft

Peter · Answer

Yes you should be ok to walk on if all flat and solid

Kyle · Answer

Short answer: sometimes yes, but don’t assume it’s safe—flat felt garage roofs can look solid and still be weak underneath.

🏠 What matters most

It’s not the felt you’re walking on, it’s what’s under it:

* Joists (timber size & spacing)
* Decking (OSB/ply vs old chipboard or thin boards)
* Condition (rot, water damage, sagging)

A 1970s garage roof can be:

* ✔️ Solid (walkable with care)
* ⚠️ Borderline (spongy / slight sag)
* ❌ Unsafe (rot, long spans, weak deck)

⸻

🚫 Red flags — don’t walk on it if you see:

* Noticeable sagging dips
* A spongy/bouncy feel
* Cracking sounds
* Signs of leaks inside (stains, mould, soft timber)
* Very thin edge boards or deflection at the fascia

⸻

✅ If you have to go up there

Reduce the risk:

* Spread your weight
    * Use a crawl board / scaffold board / sheet of plywood
* Stay near load-bearing edges or above joists (not the middle span)
* Don’t step between joists
* Wear soft shoes (avoid damaging the felt)
* Keep it quick — no jumping, no heavy loads

Saleem · Answer

what sizes are the joists, and spacing, im a roofer, the flat roof will hold ure weight, , does it have osb board underneath

Simon · Answer

If it’s only waking on the roof and your centres are every 1600
Or 16 inch should be fine as long as the boards are not rotten

Ryan · Answer

I would advise you to contact a flat roofer to inspect the condition of the structural works first.

Tim · Answer

If it's a flat roof the construction should be good enough to take a full snow loading on the roof. But you can't rely all the time that it was built in a good standard. Rafters should be at least 150mm x 50mm if it's a single garage spanning width. Your relying on who built it doing their job correctly

Ryan · Answer

Should be structurally sound and be able to withstand the weight of two people in my opinion

Joe · Answer

Depending on the rafters and the boards keep to were the rafters are but please take extra care

How much weight can a garage roof hold?

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