The software we use for calculating fastener patterns for securing a flat roofing system against the wind does not have the ability to calculate the different length tube washers and fasteners required for securing a flat roof with tapered insulation. So when carrying out the calculation, we use an average thickness to complete the calculation.

Did you know we offer a service where we can recommend the correct tube washer and fastener for securing your tapered insulation?

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When selecting tube washers and fasteners, we try to vary the tube washer length and keep the fastener length the same - to help simplify both the ordering and the installation on-site.

The wind load calculation can be used with the tapered scheme to estimate how many of each size are required.

Estimating the tube washers and fasteners required for the insulation is generally easier than estimating the quantity required for the membrane.

For the insulation you can overlay the plan of the wind load calculation, which shows the different zones (corner, perimeter & field), onto the tapered insulation drawing.

Calculating how many tube washers and fasteners are required for the membrane becomes more difficult. The quantities are dependent on which way the membrane runs (either left to right or top to bottom), as well as which direction you set out from.

The more complex the design of the tapered insulation and the shape of the building, the more challenging it gets to calculate the quantity of the different tube washers and fasteners required.

If the membrane was lap/seam fixed (which is the normal method), and ran from left to right when looking at the above plan, the tube washers and fasteners would be the same for the length of membrane (apart from the ends where the insulation changes direction). However, if the membrane ran from top to bottom, the tube washers and fasteners would constantly change, as you move over one board to the next.

Due to these complexities, we are unable to assist in quantifying how many tube washers and fasteners of the various sizes will be needed. We suggest you place an initial order and then order more as the project progresses, or spend time working it out long hand.