Description
A flat roof is never actually flat — it needs a fall, or every rain shower leaves ponding water sitting on the membrane, feeding the exact leaks and premature failures that keep our repair-kit range in business. Rather than building falls into the deck structure itself, tapered insulation boards do the job at insulation level: each board's thickness increases steadily across its width so, laid in sequence, they create a consistent drainage fall while insulating the roof.
This is the same PIR foam core and mineral-glass-fibre facing as our standard flat PIR board — the difference is purely geometric: constant thickness for pure U-value, or tapered for drainage fall plus U-value in one layer.
Specification
| Property | Detail |
|---|---|
| Core material | PIR (polyisocyanurate) rigid foam |
| Facing | Mineral-glass-fibre coated facers, both sides |
| Fall | Standard 1:60 taper |
| Board size | 1200 x 1200mm |
| Thickness bands | 30-50mm (Pack of 6, 8.64m²), 50-70mm (Single Board, 1.44m²), 70-90mm (Pack of 4, 5.76m²) |
| Application | Warm and cold flat roof build-ups needing a drainage fall to outlets/gutters |
Ordering guidance
Tapered schemes are normally laid out board-by-board along the fall direction toward your roof outlets — for anything beyond a simple single-direction fall, have your roofer or a tapered-insulation designer confirm the board layout and thickness sequence for your specific roof geometry before ordering. This range complements our standard PIR Insulation Board (constant thickness, for roofs where fall is already built into the deck) and pairs with our Polythene Vapour Control Layer and PVC Single-Ply or EPDM membrane ranges to complete a warm roof build-up.
FAQ
Do I need this instead of standard PIR board? Only if your roof needs a built-in drainage fall. If your deck already falls to outlets, standard constant-thickness PIR board is usually the simpler, cheaper choice.
What does "1:60 fall" mean? A 1:60 fall rises 1mm in height for every 60mm of horizontal run — the standard minimum fall recommended for most flat roof membranes to avoid ponding.
Can I get thicker bands than 90mm? Wider thickness bands (90-150mm) exist in this range from the manufacturer but were out of stock everywhere we checked at time of publishing — get in touch and we'll source and quote them for you.
Does thickness affect U-value as well as fall? Yes — because the boards taper, the average thickness (and therefore average U-value) varies across a scheme; a proper tapered layout calculation accounts for both fall and U-value together.
Can I cut boards to fit? Yes, PIR tapered boards can be cut on site, but cutting across the taper changes the fall gradient at that point — plan cuts along the taper direction where possible.
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