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40 Below Flashing Tape is a self-adhesive flashing tape to seal around windows, doors, and other joinery openings as a secondary defence against water penetration.

A classic, white facer tape that has excellent adhesion and a no-nonsense performance record, earning the trust of the professionals. 40 Below is compatible with most wraps and sealants so eliminates issues on-site.

Key Benefits
  • Incredible adhesion and reliable and dependable weather tightness in a wide range of conditions from -40°C up to 65°C.

  • Extremely thin (0.2mm) so allows for easier fitting of windows and doors.

  • Great value for money.

  • Simple 4-step installation. Save time reducing costs.

  • RIGID AIR BARRIERS – 40Below is tested and approved for sealing the joints on Rigid Barriers. Tested and approved for use by BGC Durabarrier and OS’BraceRAP.


New Zealand Building Code Standard (NZBC)

  • For a risk score between 0-20 in accordance with NZBC Acceptable Solution E2/AS1.

  • Passed NZS3604 Building Wind Zones up to and including ‘Extra High’.

  • Passes nail sealability to ASTM 1970-01 section 7.9.

  • New smooth white facer tape also passes screw sealability to AAMA 711-13.

  • Two layers are required on the sill for nail and screw sealability


Windows/Door/Timber & Steel Frame Flashings

  • Masons 40 Below™ Flashing Tape and Masons Corner Guards must be installed in accordance with these instructions. Ensure the 40 Below™ Tape completely covers the joinery opening.

  • To ensure maximum adhesion of the tape, make sure the substrate surface is clean, dry, and free from any dust or other contaminants. Flaps are folded into the opening and secured.

  • The building wrap is installed as shown on the exterior face of the frame. A window and door openings are cut at a 45˚ angle away from each corner, then the flaps are folded into the opening and secured.

  • 40 Below™ Flashing Tape must not be stretched. When joining 2 sections of tape, overlap by 100mm or more.


SKUs List
40 Below Flashing tape 75mm

75mm x 20m

40 Below Flashing tape 100mm

100mm x 20m

40 Below Flashing tape 150mm

150mm x 20m

40 Below Flashing tape 230mm

230mm x 20m

Available In Store

Industry Partners


How many 40 Below tape products are there?

Three, 40 Below Ultra Sticky (original) 40 Below Platinum, and 40 Below Flex

Which 40 below Tapes must be used on UNI?

Only 40 Below Platinum or Flex may be used on UNI, UNI PLUS, and UNI PRO jobs.

Can any of the 40 Below range be used on rigid air barriers?

Yes IBS and BGC allow 40 Below to be used – check the latest instructions from these manufacturers. Masons recommend 40 Below Platinum or Flex for best performance.

Can 40 Below be used with other underlays?

40 Below may be used on any underlay where a Code marked flashing tape is allowed. A small number of proprietary appraised or Code Marked underlay systems will require specific tapes - check with the manufacturer of the underlay system.

Do Masons 40 Below flashing tapes comply with the New Zealand Building Code?

Yes, compliance is signaled by a current Codemark certificate of conformity.

Where are the installation instructions?

In the downloads section of the 40 Below Tapes pages, or on the label of the 40 Below tape product

How many layers are required the sill?

40 Below Ultra Sticky (original) and 40 Below Platinum require 2 layers to the sill, 

40 Below Flex requires only one layer (self-sealing).

Do Masons blue corner soakers have to be used?

No, a corner soaker may be formed from the tape itself. Masons recommend the use of corner soakers but this is optional for most jobs. See Masons 40 Below for installation instructions.

Is 40 Below sealant compatible?

Yes, 40 Below uses modern adhesive technology and there is no incompatibility with commonly used construction sealants and adhesives. Masons have a list of tested sealants and foams in the downloads section of this website.

Will all sealants and expanding foams bond to 40 Below?

Masons have a list of tested sealants and foams in the downloads section of this website. We recommend sealant manufacturer is contacted and adhesion trials are conducted if you plan to use other than the tested and approved Soudal products for façade design or wet seals to joinery.

Where can details on temperature range or UV exposure be found ?

Masons 40 below Family brochure details this and also states the standards the tapes are tested to. Download this from the downloads section of this web page.

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