Temporary roofs: what information we need to design it safely
Temporary roofs are one of the quickest ways to turn a weather-wrecked programme back into a predictable one — but they’re also one of the fastest ways to accidentally create a “wind structure” if the design brief is vague.
Unlike a standard access scaffold, a temporary roof introduces:
large exposed surface area (wind/suction/uplift),
long spans and transfer loads (beams/trusses/ledger beams),
complex stability (ties, buttressing, plan bracing, sometimes kentledge/anchorage),
and sequencing risk (it’s weakest while being erected/struck).
NASC has specific guidance focused on temporary roofs and enclosed scaffold structures, with emphasis on loadings, weather effects, stability and sequencing.
And HSE is clear that roof work must be properly planned and managed because it’s high risk.
Below is the “designer’s shopping list” that lets us produce a roof design that’s buildable, compliant, and doesn’t unravel the moment the weather turns.
1) What type of temporary roof is it?
We need to know the roof system concept, because it drives geometry, load paths, and bracing:
Rolling (mobile) roof vs fixed roof
Mono-pitch vs dual-pitch
Sheeted roof panels vs keder / shrink-wrap / tarp systems
Spanning between scaffold lines vs independent “goalpost” frames
If you don’t know the exact proprietary system yet, that’s fine — but we need the intended arrangement and constraints so we can design the supporting scaffold correctly.
2) Geometry: the numbers that matter
Give us dimensions and levels early and everything becomes easier:
Overall length and width to be covered
Eaves height and maximum overall height
Any step changes in roof level
Required clear headroom over the workface
Any bridging requirements (over atriums, canopies, glazed roofs, plant, public areas)
Even a quick marked-up sketch is enough at enquiry stage.
3) Site exposure: “wind” is not just a forecast app
A temporary roof is, structurally, a big sail. Wind actions are typically derived using Eurocode wind principles (EN 1991-1-4) and scaffold/temporary works performance requirements sit within the BS EN 12811 framework.
So we need:
Is the site coastal, elevated, or open terrain?
Are there adjacent taller buildings (turbulence, channeling)?
Is it a tight city centre street (gusting around corners)?
Any known local wind issues (you’d be surprised how often “it always funnels here” is true)
This information influences tie forces, plan bracing and sometimes whether a “standard-ish” approach is viable at all.
4) What loads will the roof be asked to take?
Temporary roofs aren’t designed just for “being there” — they must resist actions from:
wind pressure/suction and uplift
self-weight of roof system
maintenance/installation loads
potentially rainwater ponding if drainage is poor
sometimes snow/ice considerations depending on the brief and duration (and what you’re wrapping/enclosing)
Tell us:
Do you need it watertight-ish or is it primarily weather protection?
Will there be gutters/drainage? Where does water go?
Any plant or materials hung off the roof line? (lighting, heaters, extract ducting, signage)
5) Stability strategy: ties, buttresses, kentledge, anchorage
HSE’s scaffolding guidance is explicit: scaffolds must be tied/braced/stabilised and ties must be within their safe working load, installed progressively, and controlled if removed.
For temporary roofs we need to know:
What is the host structure you can tie to (brick, block, concrete frame, steelwork)?
Any no-tie zones (glazing, cladding, heritage façades, services)?
Are you able/willing to use buttresses/rakers where tying is restricted?
Is kentledge/ground anchorage permissible (space, ground condition, public interface)?
If tie positions are restricted, it’s not a deal breaker — it just needs engineering early, not panic later.
6) What’s happening underneath?
This is the bit that kills otherwise “perfect” designs:
Is there a suspended slab or weak ground where leg loads are limited?
Are there basements, vaults, ducts, manholes or fragile roofs below?
Is the roof spanning over public areas requiring higher protection levels?
These constraints often dictate additional spreaders, grillages, or alternative support arrangements.
7) Sequencing and programme: when is it most vulnerable?
Temporary roofs are often at their highest risk during:
partial erection (incomplete bracing/ties),
transitions from scaffold-only to roof-installed,
rolling operations (if mobile),
dismantling.
NASC temporary roof guidance specifically focuses on safe sequencing.
Tell us:
Are you planning phased erection (e.g., one end at a time)?
Must parts of the scaffold remain live for access while roof is installed?
Any constraints on craneage/telehandler use and drop zones?
8) “Enclosure creep”: are you also wrapping the scaffold?
A temporary roof frequently evolves into an enclosure: “we’ll just add monoflex… then shrink wrap… then banners…”
Cladding/wrap changes wind loading and stability management, and NASC has separate guidance on cladding of scaffolds to manage wind and stability.
If enclosure is even a possibility, mention it early — it can materially change the design.
What we need from you (copy/paste enquiry checklist)
If you want the fastest route to a safe design and an accurate fee, send:
Site address + what3words + a few photos
Coverage dimensions (L × W), heights, and any level changes
Roof type (rolling/fixed, mono/dual pitch) and intended sheeting system
Exposure notes (coastal/elevated/open terrain/city centre)
Tie constraints and façade type
Ground/structure constraints (slabs, basements, fragile roofs, services)
Any enclosure intent (netting/monoflex/wrap/signage)
Phasing/sequencing constraints and programme drivers
Any special interfaces (public protection, rail, highways, crane lifts)
Bottom line
Temporary roofs are brilliant — but they demand proper wind/stability thinking and a clear brief. Give us the information above and we can produce a design that’s buildable, defensible, and far less likely to be “value engineered” into a liability on site.