Cladding Replacement Question: Wood >> uPVC

17 Jul 2017
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United Kingdom
Hi All,

I am replacing the wooden cladding on an outdoor utility cupboard (attached to the front of the house) with uPVC open-vee cladding to match the recently replaced doors and windows, now also uPVC.

I have ordered all the cladding, breather membrane etc. and have stripped the old cladding off so I can see the original construction which used 89 x 38mm battens giving adequate (89mm) air gap behind, however ... my problem is that the old breather membrane was installed OVER the battens, then the cladding directly onto the membrane. Installation details tell me that with the uPVC cladding the membrane should go behind the battens and not contact the new cladding, but I can't fit it behind the battens without virtually destroying the cupboard first and starting from scratch!

As this is retrofit and not new build, can I get away with putting the membrane directly behind the uPVC cladding or will this compromise its waterproofing function and break building regulations?

Thanks, Hugh.
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It wont matter as long as you detail the top and bottom ventilation correctly, and ensure that any joints to openings and penetrations are sealed
Thanks Woody.
Can I please just check I understand correctly - I have the cladding (to be mounted at 40 degree slope to match rest of the estate), 2-piece corner trim for the vertical edges, 2-piece edge trim for top and universal 1-piece edging for bottom. The top edge is beneath a porch roof and goes up behind porch fascias so is protected from rain, but is open to the air gap under the roof for ventilation. The bottom horizontal batten sits directly onto a single brick course, so I intended putting slots in the bottom channel for drainage in case of condensation/leaks in cladding. Is that adequate or do I need any additional sealing?

Thanks, Hugh.
Could you post a picture? I can't visualise cladding at a 45° slope.
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Hi Woody,

Yes sorry, a picture is worth a thousand words!


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I see.

As it's not part of the main house (no heated internal room) then there is no condensation risk. I can't see the benefit of a vented cavity behind the cladding either or drain holes, you could just fix the membrane and cladding directly to the frame.
That makes perfect sense . Thanks Woody, you've been a great help Hugh.

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