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Help Damproofing Door threshold/old porch?

Discussion in 'Floors, Stairs and Lofts' started by comedybob, 1 Dec 2020.

  1. comedybob

    comedybob

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    Hi all,

    Hope someone can help, desperate to sort this before christmas and can't find a local builder at short notice.

    I have a concrete area where old porch was (now internal space) the rest of house is suspended floor. I have some cold bridging which I suspect is causing some localised damp areas see sketch below (sorry - no artist).

    [​IMG]

    What is the best approach to stop the damp at the edges, cut a channel around the perimeter and fill with suitable material or dig out the whole lot and start again? Any guidance on how to fix this would be greatly appreciated!
     
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  3. tel765

    tel765

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    Thanks for the sketch but:
    Perhaps you could post pics of inside the old porch and outside?
     
  4. comedybob

    comedybob

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    of course.....(I did post some in the building section but got no response so thought I'd try here with a sketch instead....might have to use street view google for the outside as working away)
    Looking towards the door
    [​IMG]
    Looking underneath towards the door

    [​IMG]
    Corner brick detail at the door opening. Bitumen DPC is above bricks with angled drill holes in (assuming this may have been an attempt to inject damp proof course???)
    [​IMG]

    View from outside with a raised block paved step. I'm not sure if an air brick has been blocked but can't see evidence on the inside of there being one
    [​IMG]
     
  5. tel765

    tel765

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    Thanks for the pics.

    Bit of a rock and a hard place - first thoughts are to knock out the concrete, and extend the suspended floor but the fly in the ointment is the lack of an exterior step.

    No riser means no riser ventilation. However, ventilation might be sufficient from the suspended(?) side room sub-floors?

    There's also the matter of the water coming under the threshold. However, if no water ponding on the door step then a new modern threshold carefully siliconed sealed in might act as a barrier.

    If you unscrew & lift the ply, and do a few more pics of the oversite it would help.
    I noticed shreds of plastic hanging down under the ply edges - possible previous attempt to protect woodwork from damp?
    All Cu pipework needs insulating, and cables isolated from metal pipes esp hot water pipes.

    If you have damp issues in either of the bay rooms it might be because the high step is bridging any DPC?
    The other sides of the hall walls might have damp issues?
    The damp in the hall - the lower plaster needs hacking back to brick, and the rusting corner bead sawed off -
    how high to hack off is your call depending on what you reveal?
    Likewise is it the same damp issues on both sides of the hall?

    I guess that removing the concrete and extending the wood floor is the best way forward 60:40.

    Anyway, see what you think of my suggestions and come back if you want advice on what to do next?
     
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  7. comedybob

    comedybob

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    Thanks so much for the input, I was going to put a new threshold in as the door won't clear the new flooring anyway so will need some shaving off the bottom.

    The house did suffer from a lot of black mould in corners but has eased now I have unblocked three air bricks in various rooms and stopped drying clothes in the house and uncapped the roof vents which were all sealed when we moved in. They had a tyrolean render AND what i can only assume is a cement render as its pulled half the brick away when i cleared a reveal to replace a bathroom window. Its lime mortar and plaster so god knows what they were thinking?

    I will make sure to insulate the pipework and clip the cables but to be honest I hate microbore so I'm probably going to replace the lot with 15mm PEX or layflat and just put 15mm copper up to the rad tails.

    The plastic is under the screed (about 1") as a DPM but it doesn't come up the sides so the moisture is passing up into the screed via the brickwork.

    Once past the screed the bricks are bone dry (where the ply floor is)

    I will try and get the floor up over the next few days and put some pics up but if the concrete has to come out I'm gunna have a hard time convincing the mrs to do it before christmas as she wanted it all done this week *sigh*

    Thanks again for the pointers
     
  8. comedybob

    comedybob

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    Here are some more photos of the area now the ply is removed.
    The bricks below don't appear to be that damp and anything in the suspended floor area is bone dry
    [​IMG]
    The DPM strangely appears to go under the screed then down to the top course of bricks.
    [​IMG]
    [​IMG]

    We've had a lot of rain recently and the front outside step is relatively sheltered so remains fairly dry, I've no idea what's been laid underneath it, there is no DPM folded under the threshold from under the brick step, just a DPC under the door sill.
     
  9. tel765

    tel765

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    I wonder if your suspended floor ran into the outside wall, perhaps in pockets below the door threshold.

    The new arrangement of a short solid floor - but is it actually a concrete solid pad? - and then a suspended floor was introduced. Was a full membrane used?
    Rusted nail holes indicate excess moisture - typically condensation - under the suspended floor.
    You now perhaps have damp coming from under the door?
    And maybe damp from the solid floor, and/or the actual party wall, and the front elevation wall?
     
    Last edited: 11 Dec 2020
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  10. comedybob

    comedybob

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    I suspect your right!!

    Thanks for taking the time to add your thoughts.

    I think my only option is to remove the screed/concrete/backfill back to ground level. Check the front elevation for blocked up airbrick. Check the front outside step has suitable protection against the front elevation. Replace the door threshold and like you have suggested extend the suspended floor using proper joists affixed to a wallplate/hangers at the door end.

    Hack the plaster off as far as the damp extends. leave through the summer to hopefully dry out then redo the lime plaster.

    I only wanted to lay a new floor before christmas *sobs*

    Kind regards Rob
     
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