Why Choose Tapered Roof Insulation?

A flat roof should never be truly flat.

Falls should be incorporated into the roof to ensure sufficient water channelling and drainage to avoid standing water or ponding.

Problems associated with standing water on roof decks include additional weight on the structure from standing water (causing deflections to the roof’s structural deck), reduced lifetime of the waterproofing system and health & safety risks to building maintenance operatives (ice formation and moss/algae can cause slip hazards).  Standing water will most likely result in refurbishment of a roof area or even the entire roof much earlier than intended.

If the roof fall cannot be provided within the structure then the provision of a fall within a warm deck flat roof is normally achieved in one of three ways:
• tapered insulation;
• timber firrings under a plywood base; and
• screed laid to falls.

What makes tapered insulation (aka cut to falls) the best solution?

The aim of a tapered roof insulation system is to reduce or eliminate the amount of standing water or ponding on the membrane when the roof deck does not or cannot provide adequate slope.

By incorporating tapered insulation into a flat roof it allows appropriate water channelling to drainage outlets and reduces the risk of standing water. It also negates the requirement of a structural fall, which helps reduce the overall cost of the roof and installation time.

Independent studies have assessed both the cost and speed of each method. Compared with the other methods, tapered insulation offers many advantages.

Reduced costs and installation time

Estimated drying times for screed to falls systems are in the region of 100 days +, with insulation and
waterproofing installation adding further time.

Estimated installation times for a tapered insulation systems and the waterproofing membrane can typically be in the region of 50m2 to 300m2 per day (dependant upon deck type and fixing method). Also, as the insulation and falls are achieved in a single operation, site traffic on the roof is greatly reduced.

Greater flexibility

Tapered insulation is more  suitable for complex fall configurations than other methods. The insulation boards can be easily cut on site to accommodate even the most complex of roof shapes or rainwater outlet positions. Factory cut pre-mitred hips and valleys are available to make this process even easier.

Creating falls with timber firrings can be very complex to install where cross falls are required. There is also the potential for condensation risk within voids formed by the firrings.

Reduced weight

Standard sand and cement screed weighs approximately 2000kg/m3. The weight of tapered insulation systems vary, depending on insulant  type, however, all are of significantly lower weight than screeds. For example, the weight of tapered insulation using a rigid polyisocyanurate (PIR) insulant, is typically 32kg/m3.

Even using the relatively heavier rock mineral fibre, the weight is only up to 180kg/m3. Hence tapered insulation offers a huge benefit by reducing additional weight on structures.

Refurbishment Advantages

Tapered insulation provides excellent opportunities to improve roof drainage as part of roof refurbishment schemes, whilst improving the thermal performance of the roof. Schools and other flat roofed buildings constructed in the 1960s and 70s typically suffered from inadequate roof drainage or poor detail design.

Bespoke designed schemes can be provided to overcome existing back-falls, height restrictions and other issues.

If you're considering refurbishing a roof, we provide a survey service that can assess the roof and then advise you on the best course of action. Click the link below.

Tapered Insulation Products

Building Innovation

Harvey Road

Burnt Mills Industrial Estate



SS13 1QJ

+44 (0) 1926 888808