# Forum Home Renovation Waterproofing  Waterproofing of box gutter

## kesawi

Ive had a waterproofing membrane applied to the box gutters on our roof which were leaking. It rained lightly on the night the membrane was applied which had a reaction to the moisture.       
They did come back out and rectify the membrane, but it only looks slightly better.     
Is this satisfactory or does it need to be rectified?

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## sol381

Never seen that done before.. Box gutters are no different than normal gutters, just a bit crappier.. All that was needed would have been silicone along the joins.

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## wspivak

Which membrane did you use?

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## kesawi

I'm not sure which product they used. The quote only specified a non-porus primer, hybrid polymer modified PU sealant to the joints, and a UV stable moisture cured PU membrane.

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## wspivak

> I'm not sure which product they used. The quote only specified a non-porus primer, hybrid polymer modified PU sealant to the joints, and a UV stable moisture cured PU membrane.

  Ok, it's difficult to be 100% certain without all the facts, however, a few things to consider. 
1. I've never come across a hybrid polymer modified PU sealant (MS or SMX polymer) which doesn't adversely affect solvent based PU membranes (ie stops them from curing properly) - this could be the reason for all that discolouration post rain?
2. Solvent based PU membranes can't be classified as UV stable to my knowledge, however, they can be classified as UV resistant, meaning they will last longer, but will eventually wear away.  This can be alleviated through the application of an aliphatic top-coat, which doesn't appear to have been done here.
3. Based on the photos (especially one where tape is showing), it appears the application may have gone on a little thin
4. The membrane has definitely been adversely affected by the rain - hard to say exactly what the long term affects of that would be though 
Hope that helps.

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## kesawi

Found out the product was AIS liquid rubber which appears to be bitumen  modified polymer rather than a PU membrane. This would be consistent  with why the brown area is a little tacky and smells like bitumen.

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## wspivak

Well that explains the bitumen type of discolouration.  Still looks a little on the thin side in some spots though.

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## kesawi

They're coming back today to go over it with the high build version of the product.

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## wspivak

Good news then  :Smilie:

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