Damp issues on internal wall

Discussion in 'Builders' Talk' started by Adama119, Sep 16, 2021.

  1. Adama119

    Adama119 New Member

    I'd be grateful for your help.

    I live in an 1870's victorian terrace with cavity walls and a cavity floor. I currently have damp patches (wet patches between 15-30cm above the skirting) on my internal (non external sharing) walls. I have also suffered rotting floor boards in these areas in the past. All the external sharing walls are fine.

    What kind of damp would this be? I read online that rising damp rarely affects internal walls like this unless they are shared external walls. As my external sharing walls are fine this would suggest not?

    Thank you
  2. Wayners

    Wayners Screwfix Select

    Check all drains for cracks. Often cracks in the ground level drain outside kitchen or rain water down pipes drains and water runs under house or saturates ground. Cracks in the drain cement causes big problems. Simple DIY fix.
    If all good then you need to lift floor boards and inspect.

    Damp companies are hit and miss with rip off costs and I have little trust in them but there are a few that know what they are doing if you can find one. Just hold that thought when dealing with them. Get a good one they will advise and be worth the money. Its just finding one.
    ThomasAnderson and ElecCEng like this.
  3. ElecCEng

    ElecCEng Screwfix Select

    As @Wayners says, first eliminate any sources of water. By ‘sharing’ do you mean the party wall with your neighbour? Might be worth checking (if you can) that they haven’t got a leaky radiator or anything on the other side of your wall.

    Make sure you check for pipes on your side of the wall, again making sure there’s no leaks.

    You don’t need to lift the floorboards to check underneath. Either drill a small hope and use an endoscopic camera or cut a hole (multi tool or hole cutter) just large enough to fit a hand with a camera/phone through it.

    If the party wall has a cavity, you need to check the roof and attic to make sure that water is not getting in there.

    Finally rule out internal moisture. Kill any mould with a decent spray cleaner. Make sure the space is heated and well ventilated. A cheap weather station type device will help understand humidity levels in the space too.

    Do come back to us with what you find!
    Wayners likes this.
  4. Adama119

    Adama119 New Member

    You clever people!

    Okay so I suspect I have a host of possible culprits.

    Firstly ElecCeng, I meant "sharing" as in the internal wall is an external wall also on the other side. I don't have damp on any of those walls. It's just on internal only walls.

    So I drilled a hole in my floor next to my wettest wall and got an endoscope and looked below. I can see that the ground underneath is covered in white mould and there also appears to be a bit of condensation on my cold water mains pipe which appears to be uninsulated. I then realised something. I had a new front door installed about 8 years ago and there is no ventilation holes beneath it. My old wooden door used to have lots of holes below the step so I don't understand why the door company didn't drill and new ones. I'm wondering if the lack of ventilation in my hallway over the last 8 years has caused stagnant humid air to grow mould and cause the cold water pipes to sweat in summer. Lots of moisture!

    Also, I noticed the uninsulated mains pipe actually leads directly under a plastered wall and into my kitchen. This wall I also have damp on. When I took one floorboard up last week I could see condensation on this bit of pipe and again mould on the floor.

    I suspect that all these problems have been caused by the cavity under my hallway being unventilated, the mains pipe being uninsulated and lack of ventilation in my home in general over the summer months. I've drilled under my step and installed a vent and can already feel a draught under there. Also I'm going to take the floor boards up next week and remove the mould and insulate my mains waterpipe.

    Does this sound logical?

    thanks for your help!
  5. Adama119

    Adama119 New Member

    Hi, so further to my last post (yesterday) about my findings I've done research online and had another look below.

    I've found that the areas where the damp is showing in the hallway is also where rubble has piled up against the wall below the floorboards. Like mounds of it up against the wall. I read online that this could lead moisture to bypass the DPM and travel up the wall. The exact spots where these mounds are is exactly where the damp is currently and where we've had it before.
    It's also piled up around the legs of my suspended flooring joists and caused some rot.
    That surely can't be a coincidence ‍♂️.

    Anyway I've created a new vent under my front door to allow airflow, insulated all my pipes that had condensation on them and removed these pile ups of rubble above ground level that were against the walls and legs

    I'm hoping this will solve the issue now.

    Will the damp patches on the walls dry up or be present forever?

    Again thanks a lot for your help

    ElecCEng and CGN like this.
  6. CGN

    CGN Screwfix Select

    Sounds like you’re getting there. Good ventilation is key on these buildings. The old vents can be replaced with modern plastic to further increase air flow. Check external ground levels, and the usual drains, guttering and down pipes.

    The walls can take months to dry out, so keep the rooms warm(not too warm) and ventilated.
  7. Adama119

    Adama119 New Member

    Thank you CGN,

    Yes I've checked our external and given the outside vents a good clean too. I bought an endoscope camera on the recommendation of ElecCEng and will use that to have a good look inside the vents to checks they're all clear.

    One thing I did notice is that the paving flags outside in the back are not mortared in. They just have soil between them so I think this could be an issue too as moisture is likely travelling straight into the cracks and sitting underground. So I'm going to fill in these gaps too at some point. The drain appears fine and the guttering is fairly new and isn't leaking. Hopefully, a combination of all these problems being fixed will make a big difference. I'm actually pleased to find all these issues as they're things I can fix. If I hadn't found anything I'd be worrying about costs etc.

    One thing I'm unsure about is how much ventilation I should've put under my door I did one smallish vent of 5 holes at 1.5 cm diameter each. Not sure thats adequate

    Ill wait and see.
    Thanks again,
  8. GRH

    GRH Member

    Hmmm, how does the ventilation in get out again? I would say you need through ventilation to carry moist air out and dry out the area. I don't think what you have provided is adequate to be honest.
  9. CGN

    CGN Screwfix Select

    It’s about the cross flow as there will be air bricks on all sides of the house and any sleeper walls supporting the floor joists will be built to allow air through. If the air bricks are working properly then you should find quite a breeze under a suspended floor.
  10. Adama119

    Adama119 New Member

    Hi GRH,

    thanks for your pointers.

    As CGN has stated, in the floor cavity there are large gaps below where the doorways are into each room and also large holes about midway in each wall. It allows the airflow to travel the entirety of the lower house from vents at the front and out the back ones. I can actually feel an air current now so I know the air is actually moving through these channels however I think it could be stronger and could be down to the size of the small vent I've put in. I'll add another under the door.

    Its only early days and I actually found the DPM bitumen layer on the bricks and the rubble had well and truly covered it in the areas I have damp.

    Fingers crossed
  11. GRH

    GRH Member

    Hi Adama,
    Thanks for the update, sounds like you have cracked it, more airflow is definitely a good thing to have.

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