Kerabit 3700 UT Fleece

Kerabit 3700 UT Fleece is a torch-on underlay membrane, which is used mainly as waterproofing and radon insulation of foundation walls.

The membrane is reinforced with reinforced polyester. There is a polypropylene non-woven fabric on the upper surface of the product, and torch-on bitumen on the bottom side.

Thermal insulation can be attached by heating upper side of the membrane carefully, and pressing the thermal insulation on top of it.


  • Kerabit Triangular bitumen fillet

  •  Kerabit BIL 20/85 -primer

  •  mechanical fastening at the top

Manufacturer / Manufactured for Nordic Waterproofing Oy, Lohja plant
Country of origin Finland
Conformity marking CE
Reaction to fire Manufacturer’s fire testing certificate
Fire Classification


Manufacturer’s declaration of conformity Kerabit modified bitumen roofing materials
Quality control Quality control agreement between the Plant and Eurofins Expert Services Oy
Nominal thickness approx. 2,6 mm
Nominal weight 3700 g/m²
Weight of the supportive layer 170 g/m² (+/- 10 g/m²)
Supportive layer polyester
Rolls size 1,0 x 7 m / 7 m²
Need for materials appr. 6,1 m²/roll
Packages / pallet 35 rolls
Weight / package 26 kg
Weight / pallet 932 kg


The product is used for foundation waterproofing, including waterproofing under hydrostatic pressure, and radon insulation. The product is also well suited for radon insulation of basement spaces.

As far as using of torch-on membrane is allowed, Kerabit 3700 UT Fleece is also well suited for details of standing seam metal roof (e.g. upstands, valleys and chimneys), where Kerabit 2600 UB Fleece with self-adhesive edge is used as underlay.



Installation work should be performed by waterproofing professional.

Before applying the membrane make sure that substrate is suitable, dry and flat. If basement wall is made of lightweight concrete blocks it should be sealed through by thin plastering inside and outside from top to bottom up to the concrete footing. Substrate must be primered with Kerabit BIL 20/85 primer and dried.

Membrane is installed by melting plastic film and torch-on bitumen on the bottom side. Especially when installing several layers, please note that the bitumen that comes through the fabric is not a torch-on bitumen but intended for bonding the heat insulation. The tightness of the upper edge of the waterproofing is ensured with sealing mass or liquid waterproofing if necessary. In addition, adhesion of the waterproofing is always secured e.g. with plate-type fasteners or edge list.

When using e.g. Triflex waterproofing mastics for sealing the outlets, the upper surface of Kerabit 3700 UT Fleece should be heated carefully so that bitumen comes to the surface. Bitumen should be allowed to cool. Only then Triflex products can be installed.


Handling and storage

Modified bitumen membranes are to be stored on pallets in a dry and cool place. Use a plastic hood or tarpaulin for protection. When the outdoor temperature exceeds +40°C, the rolls must be protected from sunlight.