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Flat Roofing Installation
Putting Best Practice in Focus

EJOT UK has teamed up with IPS Group to address the topic of Best Practice within Flat roofing installation. The IPS Group are a leading nationwide roofing contractor and were more than happy to collaborate with EJOT to create valuable resources for use in their own installer training programme. The joint venture has resulted in two short videos with the aim of helping flat roofing installers to achieve the highest quality results when installing flat roofs using mineral wool (stone wool) and PIR insulation.

When installing the flat roof using mechanical fixings, the key to ensuring it stands the test of time and performs as promised for the building owner is to consider these three factors:
  • The wind loading required for the building
  • Your choice of fixings and how to combine them
  • The fixing pattern

Get these things clear before you embark on the flat roof installation and you will significantly reduce the risk of the roof failing within its warranty period, and lessen the chance of costly customer call-backs.

Wind loadings and fixing patterns
The fixing pattern for the fasteners and the number of fasteners needed is determined by wind load calculations.

To understand why, refer to the guidance published by the SPRA (Single Ply Roofing Association). They highlight that the installed roof system must be able to resist the wind load induced by a building’s geometry and location.

They produce a useful checklist which you can see here: SPRA Wind Load Calculations Checklist

There are a number of different software tools available to calculate the wind loads, but make sure the methodology being used is compliant with UK Building Regulations.

How to choose and use mechanical fixings
To help installers achieve a high quality flat roof installation every time, EJOT has produced two short best practice videos showing which screw and tubewasher combinations to use and the process involved – one of the videos shows a flat roof created using stone wool (mineral wool) and the other using PIR insulation boards. Watch Best practice Video Here

Where both the insulation and membrane are to be mechanically fixed, the insulation must be installed using a 50mm diameter tubewasher with appropriate screw. Use either a hand held screw gun or drill driver with extension bar with one centre fix usually being sufficient when using stone/mineral wool, depending on wind load calculations. Lighter PIR insulation will require more fixings to secure it to the deck. Watch Best Practice Video Here

This combination can be used for fixing to timber and metal decks, but with concrete decks an application-specific combination will be needed to ensure a safe, secure result is achieved.

In every project, however, the tubewasher/screw combination must be used in accordance with the fixing pattern developed through the wind load calculations. This is absolutely critical.

Where the membrane is to be adhered, use the same process to fix the insulation to the deck but, as the SPRA advises, use a 75mm diameter tubewasher not a 50mm tubewasher. Bear in mind that a different fixing pattern may apply compared with a fully mechanically fixed approach, which the wind load calculations will confirm.

Unless you are adhering the membrane, it can then be mechanically fixed using a 50mm diameter tubewasher and screw combination. With timber and steel decks, these fixings must be a minimum of 10mm away from the membrane edge – any closer to the edge than this and there is a risk of the membrane tearing.

There are also some additional considerations when it comes to the parapets. Firstly, to get the parapet edge right, the number of 50mm tube washer/screw combinations will need to be increased along the deck fixing edge to compensate for a change in the directional lay of the membrane that will be fixed to the parapet. Alternatively, the EJOT FR Profile Bar can be used which may be preferred due to the multiple fixings and substrates it can be used with.

A different metal washer and screw combination is to be used to attach the membrane to the parapet and varying washer centres. And remember that parapets deeper than 150mm should also be insulated above the roof level.

Need further technical support?
The SPRA website is an excellent starting point to get the guidance you need to help you get flat roof installation right every time.

But EJOT can also help, especially if you need advice on the correct tubewasher and screw combination to suit the insulation, membrane and deck material.
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Installing Stone Wool Insulation

Attaching the mineral wool to the deck, the ideal tools to use, and the correct diameter tubewasher, all covered here:

Watch video

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Installing PIR Insulation

Attaching the PIR insulation boards to the deck, the ideal tools to use, and the correct diameter tubewasher, all covered here:

Watch video

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Looking for the latest product information?

Talk to a Flat Roofing Expert - Kevin Rackley, Product Manager for Flat Roofing, can update you on all new product information and offer support and advice specifically for your application​​​​​​.

M: 07720 883827
E: K.Rackley@ejot.co.uk

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