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Water under suspended subfloor void

Discussion in 'Building' started by Adam78, 27 Oct 2021.

  1. Adam78

    Adam78

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    I have a 1900s terraced house. The front room is of suspended timber floor and the back room has a concrete floor.

    The floorboards in the front room constantly keep rotting as there is water under the subfloor void and the entire room smells of damp. If i dig a hole in the subfloor void (see pics with small hole about 2 feet deep i've dug from the subfloor - water start pooling up and you can see it settle on second pic) I notice water pools up after a while so I'm thinking the street has a high water table as other neighbours have a similar problem.

    Across the road is a park and the ground level on that park is quite high (see pic)

    There are no air vents under the suspended timber floor on this property but there are some properties in the same street which have air vents fitted on the sandstone including both my neighbours on adjacent sides.

    What I have discovered is that under the subfloor void on each party wall there appears to be what I think is a vent - hardly any air flowing but what I think is that these houses were originally designed for the air to flow from the front of the property and through the air vents on each neighbours party wall and back out the front as the rear rooms are all concrete (correct me if i'm wrong). It's weird because a walk down the street reveals that some properties have air vents on the sandstone and some don't unfortunately mine doesn't have any vents at the front so I'm relying on my neighbours front vents.

    I prodded a long stick through both party wall vents and the stick passed through into one neighbours subfloor void but not the other. Speaking to the neighbour who's party wall vent appears blocked advises he's had his front room recently concreted which would explain why.

    The external ground to the front outside is flagged and is higher than the internal timber floor but does slope away from the house. There appears to be two dpcs, one above the black sandstone which you can see from outside and the original bitumen type which sits around 5-8cm beneath the sandstone and currently hidden by the flagstones. Some rainwater gathers near the garden gate (see screen shot). The guttering has also been extended up to the garden gate to take rain water away from the house.

    The dining room kitchen and bath room to the rear are all concrete and speaking the neighbours they all have the same i.e. concrete dining and kitchen. I believe this is from the original construction.

    The back street is a cobbled street with two gutters outside my house and pools quite a lot of surface water when it rains.

    Could it be that because there is park on higher ground to the front all the water isn't draining properly and accumulates at the front of these properties because the rear is all concrete?

    How can I resolve this issue of standing water in the front room?

    Some neighbours have dug a pit in the middle of the room so that all the water gathers in one place away from the walls other have layed a membrane and concreting the front room. This would mean moving all the services above the subfloor which would increase costs. I'm also concerned that if its concreted wont the water simply start rising up the walls?

    Any other advise out there of how to tackle this problem.
     

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    Last edited: 30 Oct 2021
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  3. Mr Chibs

    Mr Chibs

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    A family member has had this issue recently, I went under the floor Nearly 1.8 drop, and there was between none and 200mm of water... they are on a slope.

    without boring you, it was old mining ground, with high water table... my know it all neighbour said it’s probably built on a concrete raft (big pad) sure enough under a thin bit of soil, it is as described. Neighbours on the street, all have this, no one is worried.

    The rotten floor joists are a result of poor sub floor ventilation, air vents blocked etc. Quite easy to fix.

    how much room is there from floorboards to ground?
     
  4. Adam78

    Adam78

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    Its about 50-60cm from floorboards to ground level. The entire subfloor is sodden wet with pockets of areas where the floor dips up and down with pooling water.

    This property is also on a slope, situated in the middle of a row of terraced houses. I'm unable to open the air vents as the ground out side is higher and I think there's only one vent. If this ground was lowered and the the air vent opened up there is nowhere for the air to flow as the back room is concreted up.
     
  5. Mr Chibs

    Mr Chibs

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    Do the neighbours have the same problems with water?

    Water could be a leaking pipe, cracked drain or high water table. Does it smell excessively?

    Perhaps you need to run a dye test, but someone more experienced than I may advise you.
     
  6. Adam78

    Adam78

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    Neighbours report similar issue. The mains water comes in from the back which is concrete and can't see any issues there. Did ring united utilities who advise they don't have any assets running under the house.

    It does smell excessively.
     
  7. tell80

    tell80

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    Your front garden is getting waterlogged by water running downhill at the front garden. ive just posted a reply in the gardeners forum. i dont know if its possible to transfer the gardeners posts to here.
    Whatever else happens youve got to get through ventilation from front to rear of the sub area.
     
  8. Adam78

    Adam78

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    The garden to the front is flagged (see pic in original post). Even if I were to bring down the external ground below the internal subfloor void and open up the one air brick if it can be accessed the air is not going to flow anywhere as the back of the room which may have originaly had vents has been concreted up?
     
  9. Ian H

    Ian H

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    I would dye test all your drains and your slabs to see if anything comes through.

    I did a job next to Heaton Park and it turned out whatever water landed on the neighbours new tarmac drive, found its way into my customers sub floor.
     
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  11. jeds

    jeds

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    Air flow is vital to prevent rot and smell. The kitchen areas in 1930s houses were usually concreted but even in those days the sub-floor void of the suspended timber floors was usually ducted through the concrete to an outside wall. Are you sure there are no vents covered over? Or maybe the floor was concreted more recently by somebody that didn't install vents? Either way, a solution would be to cut through the concrete floor and install ducts/vents. It just depends on the layout of kitchen and what disruption that might cause? Ideally you'd have three vents.

    The water is a different problem. More houses than you think have excessive water under them which isn't evident because of good ventilation. If you solve the ventilation issue you may find the water issue recedes sufficiently to not be a major problem. If it remains an issue you will need to find some way of creating a drain. There are only really two options - gravity or pump. From your description it sounds like you would struggle to get a gravity drain in? Alternatively you could create a sump with a sump pump discharging to a mains drain. It's not as difficult as it sounds and loads of buildings have them.

    The vent issue is an issue regardless of the water so I would tackle that first and see what happens.
     
  12. Adam78

    Adam78

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    What I have discovered is that under the subfloor void on each party wall there appears to be what I think is a vent - hardly any air flowing but what I think is that these houses were originally designed for the air to flow from the front of the property and through the air vents on each neighbours party wall and back out the front as the rear rooms are all concrete (correct me if i'm wrong). It's weird because a walk down the street reveals that some properties have air vents on the sandstone and some don't unfortunately mine doesn't have any vents at the front so I'm relying on my neighbours front vents and that they haven't concreted their front rooms.

    I've posted a sketch of the layout of the house.
     
    Last edited: 30 Oct 2021
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  13. jeds

    jeds

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    Are there definitely no covered vents at the rear?
     
  14. Adam78

    Adam78

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    How do i dye test the slabs...do i fill a bucket full of dye and pour over the slabs and see if comes through into the subfloor void?
     
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  15. Ian H

    Ian H

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    Yes, simulate a heavy rainfall (y)
     
  16. Adam78

    Adam78

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    There definitely no vents. The dining room and kitchen are all concrete. Speaking to the neighbours they all confirm the same that the rear rooms were always concrete.

    What I have discovered is that under the subfloor void on each party wall there appears to be what I think is a vent - hardly any air flowing but what it think is that these houses were designed for the air to flow from the front of the property and through the air vents on each neighbours party wall and back out. It weird because a walk down the street reveal that some properties have air vents on the sandstone and some don't unfortunately mine doesn't have any vents at the front.

    I prodded a long stick through both party wall vents and the stick passed through into one neighbours subfloor void but not the other. Speaking to the neighbour who's party wall vent appears blocked advises he's had his front room concreted recently which would explain why.

    I've posted more pics if that helps along with a sketch of the house layout.
     
  17. jeds

    jeds

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    Lack of through-ventilation is a problem. No matter how much you reduce the water table problem, ventilation is still vital to prevent mould growth. In the long term you'll need to either introduce ventilation or concrete the floor.
     
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