
Improving drainage falls
A key consideration on refurbishment projects.
Overview
A common issue with flat roofs is their inability to shed rainwater efficiently. This can be due to:
- deficient original design
- poor workmanship
- deflection of the deck
- a combination of all of the above
During refurbishment, the opportunity should be taken to address any ponding that exists, as it is likely to cause issues in the future.
If the problem is due to a lack of rainwater outlets, consideration should be given to the possibility of adding some. However, this may often be impractical due to complications with connecting to the existing drainage system.
Where the existing roof falls are poor on a refurbishment project, tapered insulation can be used as a convenient and cost-effective way to:
- improve surface drainage
- help improve the fall
- redirect the fall to new drainage points, where feasible
However, it is not viable on every project, and we advise that you utilise the experience of your Bauder area technical manager for further advice.
Where tapered insulation is used, consideration should be given to the existing deck deflection and as to whether or not the default 1:60 falls will be enough to overcome this. This is because you may need to opt for insulation with a greater fall, e.g. 1:40, or reduce the deflection by using layers of built-up felt, hot bitumen, thin screeds, etc.
Tapered insulation
Tapered insulation example
Tapered insulation installed on a roof
FA Tapered Board sizes
Summary
Tapered insulation will ultimately create a thicker build-up to the roof system at certain points. It may also encroach on recommended upstand heights, or create a necessity to raise perimeter detailing, cavity trays, clerestory windows etc. and therefore may prove to be financially prohibitive. The other option is to add in additional outlets at the low points. However, this may not be a practical solution.
Bauder tapered insulation schemes can be designed to suit any particular project following a site survey by your Bauder area technical manager. Should this product be considered beneficial, this will be offered as an option.
Find a solution to improve drainage falls on your project
Effectively insulating a roof improves the energy efficiency of the building, reducing running costs, and has positive effects on the environment. There are different insulation options for constructing a warm roof where the insulation is encapsulated within the waterproofing system, or an inverted roof when the insulation is positioned above the waterproofing system.
We also have a range of products to support your project, including rainwater outlets.
Warm roof insulation
Rigid board insulation is located above the structural deck and is suitable for most building types. Tapered insulation can create falls for the roof.
Discover moreInverted roof insulation
Thermal insulation layer located above the structural deck and waterproofing, widely used on heavily trafficked roofs and podiums.
Discover moreProducts
Explore our full range of Bauder products specified within our solutions for new build or refurbishment projects.
Discover moreBauderECO FF
Utilising the biomass balance approach, our ECO FF insulation is manufactured from 80% biomass and renewable inorganic materials.
Find out more

Contact us today
Each project is unique in its requirements, and we have lots of resources and examples of our work available to help guide you. If you are looking for a green or blue roof solution for a new build or refurbishment project, then get in touch with our team to discuss your project’s individual needs.