420 lf non-penetrating rooftop guardrail.
A London distribution warehouse needed code-compliant fall protection around a roof that was getting routine HVAC and skylight service. The catch: the EPDM membrane carried an active manufacturer warranty with significant remaining term; any roof penetration would void the warranty in a buffer around each penetration. Solution: non-penetrating ballast-weighted guardrail, fully demountable, with no membrane contact beyond the rubber pads under the ballast bases.
The brief
Building owner had been issued a notice from their insurance carrier requiring fall protection on the rooftop service area within a defined timeframe. The carrier accepted either personal fall-arrest systems with engineered anchor points or perimeter guardrail. The owner preferred guardrail — once installed, no fall-arrest training, no compliance overhead, no per-trip risk.
The membrane warranty was the binding constraint. A penetration-based guardrail (drilled through to structural) would have voided the warranty in a buffer around each penetration. Across the 420 lf perimeter, the cumulative warranty exposure would have been substantial. Non-penetrating was the only acceptable answer.
What we built
- Total length420 lf perimeter coverage
- Guard height42" (OBC §3.3.1.18)
- Top-rail load0.9 kN / 1.0 kN public (NBCC §4.1.5.14)
- Post systemNon-penetrating modular; cast-iron base + steel post
- Base weightCounterweight engineered to resist top-rail load with safety margin
- Post spacing~8 ft o.c. typical (tighter at corners)
- Base padEPDM-compatible rubber, full base footprint
- Top & mid-rail1.5" Sch 40 pipe, galvanized
- Toe-plateNone (open-mesh perimeter; no roof-edge tools / debris path)
- FinishHot-dip galvanized
- WarrantyMembrane warranty preserved; non-penetrating system meets manufacturer's allowable-load spec
The ballast math
NBCC §4.1.5.14 sets the top-rail concentrated load (~0.9 kN non-public). For a non-penetrating system, that load has to be resisted purely by the weight of the ballast and the friction between the rubber base pad and the membrane.
The moment from the top-rail force at guard height multiplied by the base-pad lever arm gives the required vertical reaction; with a 1.5× safety factor, per-base ballast was sized accordingly. Adjacent posts also share load through the connected top rail, so the effective per-post counterweight at typical spacing exceeds the design requirement with margin.
For corner posts (where the load can't share both ways), spacing tightens and ballast increases via a stacked-base configuration. The stamped drawing called out the corner detail explicitly.
Membrane compatibility
EPDM membrane warranties typically allow rubber-on-rubber contact at low pressure. The base pads specified are EPDM-compatible, with maximum point pressure well below the membrane manufacturer's allowable. No manufacturer concern at install.
Install — 2 days
- Day 1: roof-load survey to confirm cumulative point loads acceptable on the existing structure (they were); ballast bases and post staging; primary perimeter posts set on the longer roof edges.
- Day 2: corners, mid-rails, top-rails connected; final fall-protection sign-off with the insurance carrier representative on-site.
Both days during regular weekday work hours; no shutdown, no lift work over occupied areas. Material lifted via a pick truck at ground level to the roof access stair, then carried to position.
Outcomes
- Guardrail signed off by the insurance carrier well inside the carrier's required window.
- Membrane warranty preserved; manufacturer confirmed non-penetrating system compatible at post-install inspection.
- Follow-up inspection: no base shifting, no rail loosening, no membrane wear at base pads.
Client testimonial and exact dates / metrics pending publication approval.