Why Site Specific Wind Loads Matter Before You Wrap
- Lee James
- Aug 4, 2025
- 4 min read
Updated: Jan 13
When storm-damaged sheeting flaps in the first winter gale, it’s more than an eyesore – it’s proof that wind forces were underestimated on that specific site. At EcoShrink we’re often called to re-wrap façades after “perfectly good” scaffold sheeting fails. The common thread? Site teams relied on generic Met Office data or tie-spacing tables instead of analysing how wind really behaves around their project.
This guide breaks down:
How site-specific wind loads differ from official weather station figures.
Why pressure and suction around buildings matter as much as peak gust speed
How to brief your scaffold designer so your wrapped scaffold is designed for the real loads – not just a headline wind speed
Understanding Wind Forces
Wind forces can be complex. They are not just about speed; they also involve pressure and suction. Understanding these forces is crucial for effective scaffold protection.
The Importance of Local Wind Analysis
Official weather stations record wind speeds at 10 metres above short grass in open areas. However, your site might be in a valley, on a hill, or between tall buildings. These factors can amplify or shelter wind loads significantly.
Macro vs. Micro-Climate: Terrain can funnel or block wind flow, creating hotspots just metres apart.
Surface Roughness: Urban environments, trees, and hoardings disrupt the boundary layer, leading to high-speed jets and eddies.
Thermal Bubbling & Mechanical Mixing: Solar-heated façades, crane booms, and traffic can create turbulence that isn’t captured in standard data.
Takeaway: A recorded 45 mph → 60 mph gust in open country can feel more like a “slug” of wind when it’s funnelled between tall buildings or over a parapet. The design pressure on your wrap should reflect the amplified local effect, not just the Met Office reading.
Why Tie Charts Alone Fall Short
Tie charts are still useful – but they need to sit alongside site wind assessments, trigger speeds and inspection plans, not replace them. See our Safe Working Limits guide for the operational side of wind control on wrapped scaffolds
Uniform wind profile across the elevation.
Pristine fixings and brand-new sheeting.
No progressive damage (UV, flapping, accidental nicks).
Real sites rarely meet all these criteria. Once one eyelet rips, the remaining fixings inherit extra stress until the sheet “unzips” across the bay.
Pressure in Front, Suction Behind – The Push–Pull Effect
When wind meets an obstruction, it creates positive pressure on the windward face. As the wind accelerates around corners and over the roof, it generates negative pressure (suction). In practice, that often means roof edges, corners and leeward façades need more attention in the scaffold design than the simple “front face in the wind” picture suggests.
Critical forces: roof uplift and leeward suction. Your wrap specification—film grade, weld layout, tie density—must resist both for the entire programme, not just the headline gust figure.
Shrink Wrap vs Traditional Sheeting Under Wind Loads
| Factor | Conventional Scaffold Sheeting | EcoShrink High-Tension Wrap |
|--------|-------------------------------|-----------------------------|
| Fixing method | Multiple elastic ties through eyelets (point loads) | Fully heat-shrunk membrane; loads spread across welded perimeter battening |
| Edge leakage / flapping | Overlaps & bungees allow pumped-air pockets | Drum-tight; minimal billow, lower fatigue |
| Maintenance | Ties stretch; re-tension after storms; visual inspections required | One-piece envelope resists creep; visual checks only |
| Conventional sheeting: Often needs 2–3 partial re-sheets over a 12-month programme on exposed sites. |
The key point is not that shrink wrap “defies the wind”, but that a continuous, welltensioned skin with the right scaffold design behind it spreads loads more evenly and reduces the chance of localised failure.
Practical Wind-Risk Checklist
Obtain site-specific wind data: For high-risk or complex sites, your principal designer or engineer may commission short-term mast or lidar readings, or CFD modelling. On simpler schemes, it may be enough to discuss local exposure with the scaffold designer using site photos and mapping.
Categorise exposure: Use BS EN 1991-1-4: Exposure category (open terrain, town centre, coastal, etc.) is normally determined by the structural or scaffold designer using BS EN 1991-1-4 and related guidance. Make sure your wrap supplier knows which exposure the design assumes
Consult a scaffold designer: Discuss extra bracing, buttresses, or ties before selecting any sheet or wrap. so that wrap choice and tie/bracing layout are designed together.
Select the wrap grade: Match thickness, flame rating, and reinforcement band spacing to the calculated wind pressure. in consultation with your scaffold designer and wrap supplier
Specify weld detail: Include perimeter battens, vertical joins ≤ 2.0 m centres, and mechanical fixing at load concentrations (returns, cornices). and include this in the scaffold drawings / RAMS so everyone knows what “good” looks like.
Document & inspect: Photograph welds, record batch numbers, and schedule after-storm inspections. especially after named storms or gust events above your agreed trigger speed.
This checklist is intended to help you brief your design team and wrap supplier. Final wind load calculations, tie layouts and bracing remain the responsibility of your appointed scaffold or structural designer.
Direct & Indirect Savings with Heat Shrink Wrap
Single install, full programme: Avoid the cost and carbon footprint of 2–3 replacements per 12-month programme often needs re-sheets.
Fewer call-outs in high winds: Tight skins flutter less, reducing nuisance noise and maintenance.
Wrap It Right the First Time
By recognising local wind amplification and working with your scaffold designer to choose an appropriate EcoShrink heat-shrink system – specified, welded and shrunk to match the design loads – you reduce the risk of failures, support safety and keep resheet waste out of landfill.
Want to sense-check costs as well? Use our Shrink Wrap Calculator for a ballpark installed cost, then talk to us about the wind-resilient specification
