Why Site‑Specific Wind Loads Matter Before You Wrap
- Lee James
- Aug 4
- 3 min read
When storm‑damaged sheeting flaps in the first winter gale, it is more than an eyesore, it is proof that wind forces were underestimated. At EcoShrink we are 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 local wind behaviour differs from official records;
why pressure and suction loads matter; and
how to specify shrink wrap that stays put when the weather turns.
Pressure in Front, Suction Behind – The Push–Pull Effect
When wind meets an obstruction it piles up positive pressure on the windward face, then accelerates around corners and over the roof to create negative pressure (suction). Tunnel‑like gaps between blocks generate a Venturi effect that magnifies suction on opposing scaffold runs.
Zone | Load Type | Failure Risk |
Windward face | Push / positive pressure | Sheet tearing or tie pull‑out |
Roof edges & corners | Uplift suction | Edge flipping, membrane peel‑back |
Leeward face | Vacuum suction | Sheet “unzipping” from top down |
Side elevations | Alternating push–pull loads | Uneven tie fatigue |
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.
Wind Is Local - Met Office Figures Aren’t Enough
Official stations record wind 10 m above short grass in open countryside. Your site could be in a valley, on a hillcrest or wedged between two tower blocks—all of which can amplify or shelter wind loads.
Macro vs. micro‑climate – terrain funnels or blocks flow, creating hotspots just metres apart.
Surface roughness – urban streets, trees and hoardings break the boundary layer, producing high‑speed jets and eddies.
Thermal bubbling & mechanical mixing – solar‑heated façades, crane booms and traffic churn the air, adding turbulence never seen in smooth hourly data.
Take‑away: A recorded 45 mph gust can become a 60 mph slug of wind funnelling between two buildings or surging over a parapet
Why Tie Charts Alone Fall Short
Standard tie‑spacing charts assume:
Uniform wind profile across the elevation.
Pristine fixings and brand‑new sheeting.
No progressive damage (UV, flapping, accidental nicks).
Real sites rarely tick all three. Once one eyelet rips the remaining fixings inherit extra stress until the sheet “unzips” across the bay.
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 | One‑piece envelope resists creep; visual checks only |
Wind re‑sheet risk | 2–3 replacements per 12‑month programme | Designed to last the full programme with one installation |
Practical Wind‑Risk Checklist
Obtain site‑specific wind data – short‑term mast or lidar readings, or CFD modelling for tight urban sites.
Categorise exposure using BS EN 1991‑1‑4: open terrain, town centre, coastal, etc.
Consult a scaffold designer on extra bracing, buttresses or ties before selecting any sheet or wrap.
Select the wrap grade – thickness, flame rating and reinforcement band spacing matched to the calculated wind pressure.
Specify weld detail – perimeter battens, vertical joins ≤ 2.0 m centres, mechanical fixing at load concentrations (returns, cornices).
Document & inspect – photograph welds, record batch numbers and schedule after‑storm inspections.
Direct & Indirect Savings with Heat Shrink Wrap
Single install, Full programme – avoid the cost and carbon of 2–3 re‑sheets.
Fewer call‑outs in high winds – tight skins flutter less, reducing nuisance noise and maintenance.
Wrap It Right the First Time
Wind is unpredictable, but its impact on scaffold protection needn’t be. By recognising local wind amplification and choosing EcoShrink heat shrink, drum-tight wrap - designed, welded and shrunk - you keep people safe, programmes on track and re‑sheet waste out of landfill.
