Bathroom Vapour Barrier

25 Mar 2009
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United Kingdom

We are currently creating an en-suite using space in our existing bathroom. The house is 1980's cavity wall which has been retrospectively filled with insulation.

The new en-suite walls will be stud, using MR plasterboard all round with aquapanel cement board & tanking in the shower area. It will then be fully tiled, as will the main bathroom. All existing internal walls are 100mm breeze block.

The main bathroom will then likely be battened against one or two walls to conceal pipework

My question is do I need to consider a vapour barrier at any of these points;

  • new stud wall between en-suite and bathroom
  • new partial stud wall between en-suite and bedroom (half will be stud and half existing breeze)
  • battens in main bathroom on exterior wall
  • battens in main bathroom on interior wall
I hadn't even thought about vapour barriers before but it popped into my mind.

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I only work on the commercial side and not house building but I assume the practices are the same. It's almost standard practice to create an external 'envelope' using a vapour barrier. Visqueen is the trade sheet but it's simply a polythene sheet. This is used primarily for the 'air seal' of a building as to conform to efficiency regs but equally succeeds as a vapour barrier. I'd certainly use it on the external walls but not necessary on internals as you're using MR and aquapanel boards.
One thing I would suggest is if you intend on tiling battened walls use Gypliner brackets as opposed to fixing battens direct as you can achieve a plumb finish. Even better use Gypliner studs instead of battens. Wood moves, metal doesn't. Bit more expensive but it's a tried and tested system for your application.

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