3 steps to calculate optimal fastener & sleeve combinations
Calculating the right fastener and sleeve length is vital for ensuring the longevity, performance, and safety of flat roof installations. By using the calculation methods outlined below, you can help prevent future issues and ensure the roof functions as intended.
This guide will walk you through three actionable steps to determine optimal fastener and sleeve combinations for your installation.
01 Calculating the Clamping Length (CL)
Firstly, the Clamping Length needs to be determined. This is measured by the distance between
the top edge of the substrate and the top edge of the membrane.
On a standard roof build up this would include:
- The thickness of the insulation.
- The thickness of the membrane.
- The thickness of the Air & Vapour Control layer.
Adding these together gives you your Clamping Length (CL).
Note: When you're just securing the insulation or using the isoweld fastening system, you would not need to include the membrane thickness in your calculation.
02 Calculating the Sleeve Length (SL)
The next step to determine the correct specification is to calculate the maximum Sleeve Length (SL).
This is determined by taking the thickness of your air and vapour control layer and telescopic length away from your Clamping Length (CL).
What is Telescopic Length?
Telescopic length refers to the distance between the sleeve tip and the top side of the Air & Vapour Control Layer.
This is important to consider as the sleeve & fastener need to be able to adjust and extend to accommodate for any compression of the insulation layers.
For SFS’s sleeve range we recommend a minimum of 15mm for the telescopic length.
03 Calculating Fastener Length (FL)
The last step is working out the minimum fastener length (FL).
Firstly, we need to take the maximum Sleeve Length value away from the Clamping Length (CL).
We then add the overlap of the sleeve and fastener in the sleeve. Essentially this is the amount of fastener which is contained within the sleeve.
Additionally, we need to accommodate any potential stiffeners within the metal deck e.g. 5mm, which we add on to the formula.
Calculation Complete
Once the steps have been followed you should now have your maximum sleeve length and minimum fastener length determined.
This diagram walks you through the key steps involved in the overall calculation process.
Note: Special rules apply for renovations, and in these instances, we would ask you to get in touch with our technical team at gb_technical@sfs.com.
The SFS Range
SFS’s Isotak® system offers a wide range of high-performing sleeves for membrane and insulation attachment, along with a comprehensive selection of compatible fasteners in both carbon and stainless-steel options.
3 steps to calculate optimal fastener & sleeve combinations
Calculating the right fastener and sleeve length is vital for ensuring the longevity, performance, and safety of flat roof installations. By using the calculation methods outlined below, you can help prevent future issues and ensure the roof functions as intended.
This guide will walk you through three actionable steps to determine optimal fastener and sleeve combinations for your installation.
01 Calculating the Clamping Length (CL)
Firstly, the Clamping Length needs to be determined. This is measured by the distance between
the top edge of the substrate and the top edge of the membrane.
On a standard roof build up this would include:
- The thickness of the insulation.
- The thickness of the membrane.
- The thickness of the Air & Vapour Control layer.
Adding these together gives you your Clamping Length (CL).
Note: When you're just securing the insulation or using the isoweld fastening system, you would not need to include the membrane thickness in your calculation.
02 Calculating the Sleeve Length (SL)
The next step to determine the correct specification is to calculate the maximum Sleeve Length (SL).
This is determined by taking the thickness of your air and vapour control layer and telescopic length away from your Clamping Length (CL).
What is Telescopic Length?
Telescopic length refers to the distance between the sleeve tip and the top side of the Air & Vapour Control Layer.
This is important to consider as the sleeve & fastener need to be able to adjust and extend to accommodate for any compression of the insulation layers.
For SFS’s sleeve range we recommend a minimum of 15mm for the telescopic length.
03 Calculating Fastener Length (FL)
The last step is working out the minimum fastener length (FL).
Firstly, we need to take the maximum Sleeve Length value away from the Clamping Length (CL).
We then add the overlap of the sleeve and fastener in the sleeve. Essentially this is the amount of fastener which is contained within the sleeve.
Additionally, we need to accommodate any potential stiffeners within the metal deck e.g. 5mm, which we add on to the formula.
Calculation Complete
Once the steps have been followed you should now have your maximum sleeve length and minimum fastener length determined.
This diagram walks you through the key steps involved in the overall calculation process.
Note: Special rules apply for renovations, and in these instances, we would ask you to get in touch with our technical team at gb_technical@sfs.com.
The SFS Range
SFS’s Isotak® system offers a wide range of high-performing sleeves for membrane and insulation attachment, along with a comprehensive selection of compatible fasteners in both carbon and stainless-steel options.