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Carpentry & Joinery

What underlay do you put on balcony decking which is the roof of the flat below?

Anonymous user 03/03/2024 - 3.24 PM

Hi there! I was wondering if anyone could help me out understand a bit more underlay for balcony decking as I've searched quite a bit and asked in a few shops but had no luck. I have a balcony which is on the 6 floor and is part of my downstairs neighbors flat. I chopped up the old decking and under it I found almost like a carpet or I would describe it as spongy membrane. What could that be?! I also noticed under that membrane the builders have sealed the floor with forge UPVC which I'm not sure of its properties and so on. Does anyone know what that membrane could be and what would happened if I didn't replace it like for like? I'd attach a photo but not able to on here. What is that material called? Many thanks!

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4 Answers

Liam Slaymaker Carpentry

No reviews yet

St Austell

This would almost certainly be the underlay which stops your decking rubbing away the flat roof material below which would obviously cause leaks below. So the answer to your question is, yes you would need to replace with a similar product . You would find these at most builders merchants that sell decking.

Answered8 August 2019

Anonymous user

For insulation purposes and noise.

Answered8 August 2019

Temple Tree Care and Landscapes

Rating: 4.8 out of 5

Chiswick, London

I would use an inch thick rubber matting which is normally used for back of vans or stables to lay decking on would protect the felt

Answered26 August 2019

Premier Timber And Landscaping

Rating: 4.9 out of 5

Cheltenham

Did composite decking on flats in st James square Cheltenham underlay must be sealed to prevent water seepage below

Answered31 August 2019