Water seal, weather seal or air seal? Here is a comprehensive guide for designers and engineers alike, showing you how to select the right density, width and thickness that will suit your projects needs, making sure that you get the right performance at the best possible price.

1) What is the sealing purpose?

Air and Dust seal (typical indoor applications)


Weather seal (including driven rain - most applications)


Water seal (to withstand a head of water)

Techniseal is graded by firmness, 110 being the most easily compressed (softest) and 330 being the firmest. Firmer grades will seal against more severe conditions as they exert more force on the surfaces they are compressed between, so they can withstand more pressure.

Which Grade is best for me?:

Technisea sealing chart

Other considerations:

While a firmer foam provides a better seal, there are conditions where firmness is a disadvantage. The softer foams are more conformable and will mould around sharper irregularities better. Softer foams may also be better when one of the substrates is a thin, rather flexible material, as the pressure exerted by a firm foam could cause the material to deform. Conversely, a firmer foam is better as a "spacer" between two surfaces. Diecuts are usually made from Techniseal 330.

2) What Thickness Do I Need?

The correct thickness is the one that will fill the gap when compressed by about 30% to 60%:

Gap Size (mm) Techniseal Thickness (mm)
0.5 to 1 1.5
1 to 2 3
2 to 3 4.5
2.5 to 4.5 6
4.5 to 8.5 12


3) What width do I need?

Generally, the width will be chosen to be slightly smaller than the flange or face that it is applied to. The width should also reflect the severity of the application; a wider seal can naturally withstand more pressure than a narrow seal. For guidance, we recommend the following minimum widths for roll product:

Air and dust seal 6mm
Weather seal 12mm
Water seal 25mm

Note that rolls are cut to a minimum width of 6mm, or the same as the product thickness where that is larger than 6mm.

4) Colour Options

Most grades of Techniseal are stocked in black; a few are grey - please check with our sales office.

Black, grey and white are all available, where not stocked, for a reasonable MOQ. Other colours can be made for large volume applications. Please enquire.

For all enquiries please call our sales office on +44 (0) 1628 642800 and talk to an expert!