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Damp Victorian Semi Detached - Concrete Plinth

Discussion in 'Building' started by 12Monkeys, 9 Jan 2021.

  1. 12Monkeys

    12Monkeys

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    Hi,

    I recently purchased what has turned out to be a very damp Victorian semi detached.

    Running along the whole of the extenal wall is about 6 inches of concrete plinth which was easily removed in places to reveal the dpc which is 2 bricks above the external concrete path. As you can see in the first photo some of the bricks underneath are so wet they are literally disintergrating. The rest of the plinth is firmly attached covering the dpc and looks to have been there years.

    So I am looking for any suggestions/advice on:

    1) If this is one potential source of the damp and therefore it is worth the time and effort to remove the plinth.

    2) Is the best way to remove it by hand with Hammer and Bolster

    3) Is it easy to replace any bricks that are damaged

    The damp is also not helped by the suspended timber floor having been removed at some point and replaced with a concrete floor throughout, hence why the original airbricks (2nd photo) have been filled in and also much of the old lime plaster replaced with modern gypsum - but that will be the subect of another post!

    Thanks for any help 20210108_134844.jpg 20210108_134855.jpg 20210108_134908.jpg
     
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  3. JohnD

    JohnD

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    Stand back and take a wider pic of the wall please, including the drainpipes and gullies and any manhole covers.

    It is normal in a house of that age for water leaking into the ground to make the wall wet.
    Plinth is a common way of trying to hide (it does not cure) damp at the bottom of a wall.

    It also looks to me as if old lime mortar has been washed away between the lower bricks, which is typical of long-term leaking drains. Somebody has tried to repoint them, possibly using their fingers.

    Look at the soil, paving and concrete for the areas that are wet, sunken, cracked, hollow or repaired.

    The wooden floor was probably removed because it had rotted after many years of ignored water leakage. If the leakage was from a water pipe under the floor, covering it with concrete has made it a hundred times harder to repair. Is there a water meter?
     
  4. tel765

    tel765

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    OP,

    The S&C plinth is bridging the DPC and trapping moisture.
    The whole plinth will have to be removed. All of it.
    All and any perished bricks will also have to be removed.
    If necessary, you remove & replace the bricks in short sections:
    eg. you remove say three bricks, then miss three, then remove the next three & so on.

    You have solid walls which will make it a slightly more difficult job.
    If the old DPC is breached & damaged then you would be best slipping in short lengths of overlapping DPC material.
    Or, instead, you could brick up and later use something like Dry Rods ( I have my doubts about these chemical rods but they are probably the best of a bad bunch).

    FWIW: you will never know if the above remedial work has been successful until the interior damp is also taken care of.
     
  5. 12Monkeys

    12Monkeys

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    Thanks for the replies which gives me a few things to think about - I will post a couple more pics tomorrow when next back at the house.
     
  6. 12Monkeys

    12Monkeys

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    There is a crack in the concrete path where the plinth was falling off and bricks are most damaged. The main drain runs to the right of this down the alley between the house. Next door currently has the scaffolding up and I am guessing the alleyway is generally damp as would get virtually no sun. I will be checking all the guttering this weekend as believe they will need to be cleared out. If I go ahead and remove the plinth would I also need to dig up part of the concrete path and install a french drain or similar to allow water to drain away from the alley?
     

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  7. JohnD

    JohnD

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    So you say there are no drains or pipes along the wet wall?

    Does water collect on the paving beside the wet wall?

    I can't see cracks in your pics.
     
  8. 12Monkeys

    12Monkeys

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    There are no pipes of drains along the wall - just the downpipe on the corner by the French doors. As far as I know water does not lie in the alley or by the back door where the damp is worse, but there are two chimney brests in wall that forms the alleyway and both have damp plaster low down
     

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  10. sxturbo

    sxturbo

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    Crack in path is on purpose, someone has dug and buries something there.

    Your steps will need to be removed also as it looks like they are bridging the damp course too.

    The concrete floor, has this had dpm installed?

    Is it also bridging the damp course internally?
     
  11. 12Monkeys

    12Monkeys

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    The internal concrete floor goes right to the walls so I am chiselling a channel so there is some sort of air gap. I have no idea if a dpm is present - how far below the floor surface should this be?
     
  12. 12Monkeys

    12Monkeys

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    There is a downpipe on that corner so I am assuming that a pipe is buried there to take the water in to the main drain
     
  13. sxturbo

    sxturbo

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    It should go up the side of the wall, but also between 3&4 inches down into the screed, otherwise you will get damp permiating through the floor.
     
  14. sxturbo

    sxturbo

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    Is it a rain water downpipe?

    It might not go down into a drain, it might go into a poorly designed or broken soakaway.
     
  15. JohnD

    JohnD

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    Which corner?

    Stand back and take a wide pic please.
     
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