How to select the correct tube and fastener
To optimise the benefits of the tube fastener system, the ideal combination is the use the maximum tube washer length, and the minimum fastener length available. This both eliminates heat loss through the metal fastener, and is more cost-effective as long length fasteners tend to cost more than long length tube washers
First, work out the tube length. To select the tube length, deduct 15mm from the total roof build-up, which allows for insulation compression, and choose the tube of that length or shorter.
Next, the fastener length. Take the total roof build-up, and deduct the length of the selected tube fasteners. Then, add the deck penetration/embedment length (see table further down this page), and then add 25mm for to allow for the length of fastener in the tube. Then select the fastener of this length or longer.
Example - fixing 120mm insulation to 0.7mm steel deck
Tube Calculation | |
Insulation thickness | 120mm |
-15mm (to allow for insulation compression) | 105mm |
Maximum tube length | 100mm |
Use tube washer: | SF-T-75 x 100 |
Fastener calculation | |
Insulation thickness | 120mm |
-100mm (tube length) | 20mm |
+15mm (penetration through steel deck | 35mm |
+25mm (amount of fastener in tube washer) | 60mm |
Minimum fastener length | 60mm |
Use fastener | SF-RS-SSA4-4.8 x 60 |


Penetration/Embedment depths for standard deck substrate types
Application | Penetration / Embedment |
Steel decking | 15mm through underside |
Plywood | 18mm minimum thickness, 12mm through the underside |
Timber decking | 25mm minimum thickness, 12mm through the underside |
Timber joists | 35mm embedment |
Structural Concrete | 25mm embedment |
SureFast selector chart
Steel Deck | Concrete Deck | 18mm plywood or OSB | |||||
Insulation thickness (mm) | Tube Length (mm) | Drive Bar Length (mm) | SF-RS-SSA4-4.8 | SF-RS-5.8 | SF-RS-6.1 | SF-RS-5.8 | SF-RS-SSA4-4.8 |
40 | 25 | 50 | 60 | 55 | 75 | 75 | 80 |
50 | 25 | 50 | 80 | 65 | 75 | 85 | 80 |
60 | 25 | 50 | 80 | 75 | 85 | 95 | 100 |
70 | 50 | 150 | 60 | 65 | 75 | 75 | 80 |
80 | 50 | 150 | 80 | 75 | 85 | 85 | 100 |
90 | 75 | 150 | 60 | 55 | 75 | 75 | 80 |
100 | 75 | 150 | 80 | 65 | 75 | 85 | 80 |
110 | 75 | 150 | 80 | 75 | 85 | 95 | 100 |
120 | 100 | 150 | 60 | 65 | 75 | 75 | 80 |
130 | 100 | 150 | 80 | 75 | 85 | 85 | 100 |
140 | 125 | 200 | 60 | 55 | 75 | 75 | 80 |
150 | 125 | 200 | 80 | 65 | 75 | 85 | 80 |
160 | 125 | 200 | 80 | 75 | 85 | 95 | 100 |
170 | 150 | 200 | 60 | 65 | 75 | 75 | 80 |
180 | 150 | 200 | 80 | 75 | 85 | 85 | 100 |
190 | 175 | 300 | 60 | 55 | 75 | 75 | 80 |
200 | 175 | 300 | 80 | 65 | 75 | 85 | 80 |
210 | 175 | 300 | 80 | 75 | 85 | 95 | 100 |
220 | 200 | 300 | 60 | 65 | 75 | 75 | 80 |
230 | 200 | 300 | 80 | 75 | 85 | 85 | 100 |
240 | 225 | 300 | 60 | 55 | 75 | 75 | 80 |
250 | 225 | 300 | 80 | 65 | 75 | 85 | 80 |
260 | 225 | 300 | 80 | 75 | 85 | 95 | 100 |
270 | 250 | 300 | 60 | 65 | 75 | 75 | 80 |
280 | 250 | 300 | 80 | 75 | 85 | 85 | 100 |
290 | 250 | 300 | 80 | 85 | 100 | 95 | 100 |
300 | 250 | 300 | 100 | 95 | 100 | 105 | 120 |
The above table details the most common insulation thicknesses but insulation up to 500mm thick can be accomodated. Please enquire for assistance.