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Conservatory and internal wall damp

Discussion in 'Building' started by taufiq, 1 Jan 2008.

  1. taufiq

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    Hello! I have a conservatory on the south-facing aspect of the house (catches most of the rain). I had cavity wall insulation installed a few months ago. I recently note a damp patch on the bedroom wall above the conservatory, and patches running down the conservatory wall which is adjoining the house - I think this this wall is a 'dry-wall' ironically (plasterboard over the house bricks). I've noticed that the height of the damp patch in the internal wall roughly corresponds to the level of the centre support of the conservatory roof. Do you think it could be due a defect of the conservatory roof lead flashing or another problem? Thanks!
     
  2. JerryM

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    the observations suggest a few possibilities due to the differing heights of the damp patches (above 1st floor and above ground floor). i don’t believe the cavity insulation to be a factor unless the installers damaged the building fabric in some way. although i think this possible it's also unlikely. it's more likely general wear & tear.

    the bedroom could be caused by an over flowing gutter or rain water escaping from drain pipe before reaching ground level. you need to go outside when it's pouring down and see if there are any clues. if the damp is near a window then the mastic seal around the brickwork may need repair (i had similar below a window due to cracked limestone lintel).

    the adjoining wall is below the flashing's which are notorious for letting water in if they have failed in any way (usually mortar holding the flashing in the wall drops out or cracks). more often than not this would show up more as a damp patch on the ceiling below the flashing and not on the adjoining wall. another possibility is a cracked roof tile above or close to the adjoining wall. my gut feeling is that your guttering (from roof to ground) is not working properly unless there is a fault in the conservatory. It's also possible that water is getting into the main building cavity (typ overflowing gutter at eaves, defective mastic around windows, hole in mortar or brickwork) and then entering the roof space adjacent the adjoining wall).

    all i can suggest is to have a good look around when it's raining. if there's nothing obvious then to get anywhere you would need to trace the water route by removing step by step bits of the fabric of the house ie ceiling/tiles/flashing etc.

    i think if this is the case then you should get a couple of builders in for their thoughts and quote. Don’t leave it to long as timber is also likely to be getting wet and rot can set in after 8 weeks. It would then become a much bigger problem and ££’s
     
  3. taufiq

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    Thanks JerryM! I asked a builder friend to come and have a look at the problem. He made a startling discovery - the people who constructed the conservatory before I moved in had not folded the top of the lead flashing between the bricks! All they had done was to fix the tops of the flashing to the mortar and sealed it with silicone to make it look like they had worked to standard! The reason for the damp is that the silicone had started to crack and allowed water to seep between it and the brickwork. The damp probably travelled into the inner wall because of the newly installed cavity wall insulation, and also seeped down under gravity, in between the brickwork and the conservatory plasterboard. Not unexpectedly, I'm having difficulty finding the builder who did this work.
     

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