Is Compriband waterproof?

[Dunc]

As title, really. Is Compriband supposed to be 100% (for want of a better term) waterproof? Does it need anything like silicone in addition?

 

My windows are fitted with a ribbon of Compriband to seal against the reveal at the outside. This is in a timber frame, with the window set back 90mm back from the face of the kit. I dont have the timber cladding in place around all of them yet. After yesterday's fierce winds and pretty much 24hrs of rain I have water running in at one of the windows. The windward side Compriband is sopping wet; water can be squeezed out when puching it with a finger tip. I can't see the back of it as the airtightness membremane is already in place on the inside, but this makes me wonder if this is how the water got in. 

 

Rather concerned to have to rely on the cladding and reveal boards for waterproofness! 

 

 

[SimonD]

All of these tapes come in different thicknesses each of which has a specified compression measurement for water tightness, air tightness, wind tight etc. - e.g. thickness of 25mm, watertight to 12mm, air tight to 20mm. This means that even after expansion into the gap it should be fairly compressed to be water tight.

 

I don't suppose you have any way of knowing what the installers used?

[Mr Punter]

You can tell by giving it a prod with your finger.  If it is fairly stiff it is compressed.  Soft and squishy and they should have used a wider one.  Also, make sure it is proper Compriband, not a cheaper lookalike.

[Dunc]

Ah. 

No idea what brand or dimension was used.

Definitely soft and squishy

Sounds like it needs replacing.