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Article Date: 10th February 2017

SIG Design and Technology - Flat Roof Specifier Checklist Part 2: Design Factors – Aesthetics & Structure

Flat Roof Specifier - Flat Roof System - Flat Roof

SIG - Flat roof specifier checklist

In January we introduced our Flat Roof Specifier Checklist and looked at the requirements your client might have. This week we begin talking about the design factors, starting with Aesthetic requirements and Roof Structure.

Choosing the right flat roof system can be a challenge, but ask the right questions and you’re half way there. Let us have a look at the first design questions and see how they might affect your product choices.

Q4 Flat roof aesthetics: What aesthetic do you want to deliver?
Ask yourself whether the roof will be visible at all, and from what angle. Will it be simply seen from a distance, or from close to? What are your flat roof aesthetics?

Do you need the roofing material to marry in with some existing material, structures, or cladding? Does it need to imitate a previous or existing covering, such as lead or copper? Are there any planning constraints that might require a similar aesthetic, material or colour match?

Your roof may also have a function which has aesthetic implications, for example if it is a podium deck, will it be used as an amenity space? Do you need the roof to help the building hide in the landscape?

Give your answers here and they will suggest some products in preference to others. For example if you want a coloured roof finish and later single ply is chosen, PVC will give you the widest range of colour options.

Q5 What roof structure are you dealing with?
The chosen construction of a building is a very good indicator of the ideal roof structure and waterproofing solution.

Commercial or industrial units are frequently built using large, lightweight steel frame structures, and large residential low rise are sometimes lightweight timber frame. These lightweight structures give you less freedom with roof loading and would favour lightweight roof structures and finishes.

Other buildings such as high rise residential, public and civil buildings such as hospitals may be constructed using dense masonry where a heavier roof structure is possible and may be desirable when other factors are taken into consideration such as longevity and protection.

For example, on dense concrete structures where access is required, one might consider hot melt or liquid more favourably than single ply, as the membrane would usually be buried with ballast on top. Whilst single ply can be used in this situation, special attention would need to be paid to protecting the membrane both during and after installation, which makes its use more complicated.

Identify the likely construction as concrete, steel or timber, and consider the size of spans, and this information will lock out some waterproofing options and suggest others.

Drainage, Insulation and Upstands
Next time we will be looking at questions of drainage, falls, and how these impact on your choice of roof finish. If you’d like to receive an email when the next post is published, please use the email option below to provide your email address.

How to get your Flat Roof Specifier Checklist
Would you like a copy of the checklist to use yourself? You can download a copy here, or get in touch if you’d like some encapsulated ones with drywipe pens.

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