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  • FIRST POST
    • TranceNRG
    • By TranceNRG 22nd Sep 16, 11:10 PM
    • 274Posts
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    TranceNRG
    Damp issues in my new flat - French drain or reduce ground level or both?
    • #1
    • 22nd Sep 16, 11:10 PM
    Damp issues in my new flat - French drain or reduce ground level or both? 22nd Sep 16 at 11:10 PM
    Hi everyone,
    I have some damp issues (though not huge still annoying and I see paint bubbling up in some areas) in my ground floor Victorian flat (I think - built in early 1900s). When I had the building survey done, it highlighted the ground level at the back of the house being too high. I have a patio made up of bricks on one side and concrete blocks on the other side of the building.

    Recently I decided to get my garden done and at the same time do something about the damp issues. I've had a few quotes from landscape gardeners for following options:

    1. Leave the current patio but dig out around the house and install a french drain

    2. Remove the current patio, dig out further and build a new patio with sandstone plus a french drain around the house

    Option 1 costs about 2K and option 2 costs about 5.5K (both options include clearing the garden, laying turf and creating flower beds).
    Obviously option 2 will look much nicer and it will add more value to the house but having done a full refurbishment, I am still under a bit of financial pressure so it's not an easy decision.

    However if I go for just a french drain (option 1), I don't want to later find out, it hasn't solved the problem.

    I know there's a lot of people here with experience/knowledge in damp problems and how to prevent it so would love to hear your opinion on what would work in my situation.

    Will I be able to get away from having just a french drain (but higher ground level)?

    If I go for reduced ground level and new patio, do I still need a french drain? Could I get away from not having a french drain? I wonder not having to install a french drain will save much money?

    Thanks in advance for any input.
Page 1
    • anselld
    • By anselld 23rd Sep 16, 6:53 AM
    • 4,711 Posts
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    anselld
    • #2
    • 23rd Sep 16, 6:53 AM
    • #2
    • 23rd Sep 16, 6:53 AM
    Is there a visible damp proof course and does the proposed new patio level come comfortably below that DPC?
    • TranceNRG
    • By TranceNRG 23rd Sep 16, 8:00 AM
    • 274 Posts
    • 74 Thanks
    TranceNRG
    • #3
    • 23rd Sep 16, 8:00 AM
    • #3
    • 23rd Sep 16, 8:00 AM
    Hi anselld, no the damp proof course is not visible. Is it possible that there was no DPC installed?

    I think the new patio will be 10cm+ lower than the current level.
    • Mr.Generous
    • By Mr.Generous 23rd Sep 16, 8:13 AM
    • 483 Posts
    • 476 Thanks
    Mr.Generous
    • #4
    • 23rd Sep 16, 8:13 AM
    • #4
    • 23rd Sep 16, 8:13 AM
    On a victorian build you wont see a dpc, it was generally done with layers of slate. 100+ years later its never going to be fully effective. The chemical stuff you inject into the mortar has been 100% effective for me, but doing it requires plaster off to 3ft / 1mtr and re plaster with a damp proof mix of plastering sand, cement and chemical additive.
    Anything done outside will help, but probably not cure entirely. If the ground level or patio is too high outside this would be my first job, I'd hate to do the damp work and not give it a chance. Are your floors downstairs timber or solid? Seen hard floors put in that draw damp too.
    • Apodemus
    • By Apodemus 23rd Sep 16, 8:22 AM
    • 201 Posts
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    Apodemus
    • #5
    • 23rd Sep 16, 8:22 AM
    • #5
    • 23rd Sep 16, 8:22 AM
    With a Victorian Property it is quite possible that there is no DPC. What is the construction - brick or stone? French drain or ground level at least 6 inches below the joist ends is probably the answer (don't get suckered into any expensive pseudo-solutions without doing a lot of research into their validity).

    Properly done each of your options should provide a solution but the lower ground level should be more certain and more likely to be permanent.

    If I were you I would join the period property forum (https://www.periodproperty.co.uk/forum/index.php) and ask the question there - stacks of threads on exactly this situation.
    • ThemeOne
    • By ThemeOne 23rd Sep 16, 8:23 AM
    • 599 Posts
    • 442 Thanks
    ThemeOne
    • #6
    • 23rd Sep 16, 8:23 AM
    • #6
    • 23rd Sep 16, 8:23 AM
    Any property built before 1935 might not have a DPC, it depends on area and builder really.
    • TranceNRG
    • By TranceNRG 23rd Sep 16, 10:28 AM
    • 274 Posts
    • 74 Thanks
    TranceNRG
    • #7
    • 23rd Sep 16, 10:28 AM
    • #7
    • 23rd Sep 16, 10:28 AM
    Thanks for all your input so far. In answer to one of the questions, tt's a brick house. Having recently done a full refurbishment it's not an option to hack off plaster and do any damp proofing work inside.

    I will ask the question in that forum

    If I do go for the new patio with lowered ground level, will I still need a French drain around the house? or is that unnecessary once the ground level is lowered?
    • G_M
    • By G_M 23rd Sep 16, 11:48 AM
    • 36,014 Posts
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    G_M
    • #8
    • 23rd Sep 16, 11:48 AM
    • #8
    • 23rd Sep 16, 11:48 AM
    My property is 1851.

    If I lift a ground floor floorboard I can see the floor joists, and walls, are sitting on slate. This acts as a dpc. From outside you can't see anything.

    I also had a damp problem originally as previous owners had built up a beautiful rockery against the front wall. Removed that and dug a ditch about 1 foot wide along the exterior wall. About 2 foot deep and half-filled with gravel.

    I'm sure that does not comply with current standards but

    * very little in this house does comply and
    * no more damp so who cares?
    • Apodemus
    • By Apodemus 23rd Sep 16, 11:58 AM
    • 201 Posts
    • 130 Thanks
    Apodemus
    • #9
    • 23rd Sep 16, 11:58 AM
    • #9
    • 23rd Sep 16, 11:58 AM
    My property is 1851.

    If I lift a ground floor floorboard I can see the floor joists, and walls, are sitting on slate. This acts as a dpc. From outside you can't see anything.

    I also had a damp problem originally as previous owners had built up a beautiful rockery against the front wall. Removed that and dug a ditch about 1 foot wide along the exterior wall. About 2 foot deep and half-filled with gravel.

    I'm sure that does not comply with current standards but

    * very little in this house does comply and
    * no more damp so who cares?
    Originally posted by G_M
    What you did sounds perfectly correct to me. Unfortunately all too often people spend huge amounts of money on all manner of internal solutions that may mask the problem for a few years but don't actually solve the problem! I fell foul of this myself by following the mortgage conditions on my property, before I learned more about old buildings.
    • TranceNRG
    • By TranceNRG 23rd Sep 16, 12:47 PM
    • 274 Posts
    • 74 Thanks
    TranceNRG
    My property is 1851.

    If I lift a ground floor floorboard I can see the floor joists, and walls, are sitting on slate. This acts as a dpc. From outside you can't see anything.

    I also had a damp problem originally as previous owners had built up a beautiful rockery against the front wall. Removed that and dug a ditch about 1 foot wide along the exterior wall. About 2 foot deep and half-filled with gravel.

    I'm sure that does not comply with current standards but

    * very little in this house does comply and
    * no more damp so who cares?
    Originally posted by G_M

    Hi G_M, so that's like a french drain right? Do you think this would be sufficient to reduce the moisture going in to the building? I mean my current patio looks OK (though a new sandstone one would look much nicer but it's also about 4K more expensive) but I don't want to spend the extra money and get the ground level lowered and a new patio and a french drain if I can simply keep the current patio and install a french drain.

    I think the chap mentioned removing a row of bricks along the wall in the current patio to create the french drain. So that would be about 15cm wide. Would that be enough?

    And finally, if I do decide to have a new patio and get the ground level reduced, will I still need a french drain along the walls of the house?
    • david1951
    • By david1951 23rd Sep 16, 1:09 PM
    • 199 Posts
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    david1951
    There is an element of trial and error. The first place to start would normally be the cheapest option (dig a ditch and put some gravel in) and go from there.

    I'm no expert but I think a French drain would be the ditch + gravel but also an underground pipe buried in the gravel that collects water flowing into the drain, and takes it away from the house.

    There is no silver bullet but often the simplest solution can be the most effective.
    • TranceNRG
    • By TranceNRG 23rd Sep 16, 1:14 PM
    • 274 Posts
    • 74 Thanks
    TranceNRG
    There is an element of trial and error. The first place to start would normally be the cheapest option (dig a ditch and put some gravel in) and go from there.

    I'm no expert but I think a French drain would be the ditch + gravel but also an underground pipe buried in the gravel that collects water flowing into the drain, and takes it away from the house.

    There is no silver bullet but often the simplest solution can be the most effective.
    Originally posted by david1951
    Hi David thanks. Yes this is the simplest and cheapest option however if it doesn't' work then I'll have to end up forking another 4K or so remove the patio, lower the ground level and add a new patio. I'd rather get it right the first time so that's why I'm asking people hoping that some have been in this situation. My landscape gardener (who seems like a nice guy and he's been recommended by a mate) is not convinced the french drain will resolve the issue considering the ground level is quite high but then again he'll get a lot more money if I go for the new patio option.
    • david1951
    • By david1951 23rd Sep 16, 4:15 PM
    • 199 Posts
    • 213 Thanks
    david1951
    Hi David thanks. Yes this is the simplest and cheapest option however if it doesn't' work then I'll have to end up forking another 4K or so remove the patio, lower the ground level and add a new patio. I'd rather get it right the first time so that's why I'm asking people hoping that some have been in this situation. My landscape gardener (who seems like a nice guy and he's been recommended by a mate) is not convinced the french drain will resolve the issue considering the ground level is quite high but then again he'll get a lot more money if I go for the new patio option.
    Originally posted by TranceNRG
    I chipped in as I am kind of in the same boat, in that my outdoor levels are too high. The pavers in the back garden are at the level of the air brick which is not a good thing. However, I don't have any damp so I'm in no rush to fix it. Keep us updated with whatever you do, especially if it works or not (even if a few months down the line).
    • TranceNRG
    • By TranceNRG 23rd Sep 16, 5:27 PM
    • 274 Posts
    • 74 Thanks
    TranceNRG
    I chipped in as I am kind of in the same boat, in that my outdoor levels are too high. The pavers in the back garden are at the level of the air brick which is not a good thing. However, I don't have any damp so I'm in no rush to fix it. Keep us updated with whatever you do, especially if it works or not (even if a few months down the line).
    Originally posted by david1951
    will do David. I'm going to take a few days to decide - going to have to ask around more as it's a lot of money. I want to get this right and not spend money on unnecessary things as I'm still recovering from financial pressure after doing a full refurbishment.
    • TranceNRG
    • By TranceNRG 25th Sep 16, 8:09 PM
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    TranceNRG
    Does anyone else want to add anything else?

    In summary should I

    1. Keep current patio but have a french drain around the house (remove a row of bricks to create the french drain)

    2. Remove, current patio, lower ground level, have a french drain with a new patio - is a french drain needed if the ground level is lowered?

    Thanks.
    • G_M
    • By G_M 25th Sep 16, 8:36 PM
    • 36,014 Posts
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    G_M
    A French drain or weeping tile is a trench filled with gravel or rock or containing a perforated pipe that redirects surface water and groundwater away from an area. A French drain can have perforated hollow pipes along the bottom to quickly vent water that seeps down through the upper gravel or rock.
    To me, a French drain is "a perforated pipe" that carries water away to...... somewhere else, whilst also letting it seep out through the holes and soak down .

    However, if it's also "a trench filled with gravel" then, yes, I installed a French drain!

    I don't think it matters whether you do 1) or 2) above, provided the ground/soil/slabs whatever are not touching the property walls above the recommended level - that is what causes water to seep through (penetrate) the walls and cause internal damp.

    Of course if the general lie of the land means that there is a slope leading down towards the property (eg it's built on the side of a hill), then you get an adiional prospective problem: not just penetrating damp from adjascent soil, but possibly surface water running down against the property wall. If that's the case, yes, you need some way to re-direct that surface water or drain it away.

    But this does not sound like your scenario.
    • Apodemus
    • By Apodemus 25th Sep 16, 9:48 PM
    • 201 Posts
    • 130 Thanks
    Apodemus
    A French drain can be just a gravel-filled trench or a gravel-filled trench containing a perforated pipe.

    In option 2, if the new ground level is a bit below the level of your joists, you might not need the French drain - but the additional cost of digging it while the rest of the work is going on is likely to be relatively little, so I would still go for it.

    In your position I think I would give option 1 a try first.

    A question, though... Where does the water from your down pipes go? And are you sure that this water is not contributing to the problem? If you do either of your two options, what effect will this have on your down pipes and their soakaways/waste pipes?
    • TranceNRG
    • By TranceNRG 26th Sep 16, 12:30 PM
    • 274 Posts
    • 74 Thanks
    TranceNRG
    House is built on flat land and I think the current patio is sloped away from the house.

    In regards to down pipes, the water all goes in to the main drain so I don't think this is causing damp and I can't see any guttering leaks.

    Are there any adverse effects of lowering the ground level around the house (and having a french drain as well)? Could the foundation be too dry and could that cause problems?

    Thanks.
    • TranceNRG
    • By TranceNRG 27th Sep 16, 12:52 PM
    • 274 Posts
    • 74 Thanks
    TranceNRG
    House is built on flat land and I think the current patio is sloped away from the house.

    In regards to down pipes, the water all goes in to the main drain so I don't think this is causing damp and I can't see any guttering leaks.

    Are there any adverse effects of lowering the ground level around the house (and having a french drain as well)? Could the foundation be too dry and could that cause problems?

    Thanks.
    Originally posted by TranceNRG
    Could someone please answer this?
    • G_M
    • By G_M 27th Sep 16, 1:05 PM
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    G_M
    Not that I know of.
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