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General: Preventing water ingress in a stone building

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  1.  
    • CommentAuthorJulesS
    • CommentTimeDec 1st 2023
     
    Hi GBF. We're in the process of renovating an old stone building (600mm rubble cavity stone walls).
    The building is cut into a hillside with a narrow void between the rear wall and the hill, over the years this void has filled in with earth. Directly behind the building is a road (single track).

    Our problem is there is a lot of water finding its way into the building. In an ideal world we'd dig out the void down to below final floor level and install a drain to move the water away before it gets to the building. However because the road is so close to the back of the building if we dig it out we'd be worried about undermining it. In the long term we want to insulate externally (wood fibreboard), so getting down to this level would be awesome.

    From an inspection pit we can see that the original depth of the void is about 60cms higher than the final floor level so if we did dig down we'd be going lower than they originally did. There is some evidence of a retaining stone wall holding the bank back, but it's in very bad condition and has been pushed about by trees.

    Digging out the void will be difficult as there's no real access for machinery, so probably would have to be done by hand.

    Our current thoughts are: dig it out section by section to below eventual floor level installing a drain, put a porous membrane in and backfill with gabions filled with FGA to the original void level... I've no idea if this is a good idea or feasible, we've come to this by chatting it over with our architect and an SE. I've attached an indicative section of this.

    I would love folks' opinions on this, and am open to any ideas on how to tackle it. We'd also be really grateful if folks could suggest a professional with specialism across old buildings, civil engineering (?) and drainage we could get advice from, as we're really struggling to get specific help with this.
    • CommentAuthorJulesS
    • CommentTimeDec 1st 2023 edited
     
    Now with attachment.. :)
      void_diagram.gif
    •  
      CommentAuthordjh
    • CommentTimeDec 1st 2023
     
    Is it a normal public road, although single track?
  4.  
    I'd forget wood-fibre if there is the slightest chance of 'unintentional fill' happening again. By all means use WF above, but consider HD EPS where it is vulnerable. You don't want to do composting experiments.
    • CommentAuthorphiledge
    • CommentTimeDec 1st 2023
     
    You might be best speaking to a local ground works contractor as they'll likely know the soil conditions and what they could excavate for you. There's all manner of machines available and I've seen excavators with horizontally hinged booms/dippers that allow the machine to excavate tight up to and parallel with a wall. Not sure how wide your " narrow void" is but it can't be too narrow to be hand excavated so likely you'd get in with a trenching bucket.

    If your section is in proportion then it looks to me like you'd have no problem getting down to your foundations without short term undermining of the road, but....there's the issue of retaining the land between the road and your wall. If there's an existing retaining wall its likely being partly supported by the filled void bearing on your house. If your house is structurally up to it then no harm in filling the void with insulation, but if it's not then you'll be opening a structural can of worms compounded with uncertainty over the boundary!!
    • CommentAuthorJulesS
    • CommentTimeDec 2nd 2023 edited
     
    Hi All,

    Thanks for your responses...

    Posted By: djhIs it a normal public road, although single track?


    yes, public road. Very low traffic, but occasionally very heavy farm machinery etc.

    Posted By: philedgeIf your section is in proportion then it looks to me like you'd have no problem getting down to your foundations without short term undermining of the road, but....there's the issue of retaining the land between the road and your wall. If there's an existing retaining wall its likely being partly supported by the filled void bearing on your house. If your house is structurally up to it then no harm in filling the void with insulation, but if it's not then you'll be opening a structural can of worms compounded with uncertainty over the boundary!!


    The section is correct for that section :). But it narrows significantly to a point where the road edge is about 90cms away from the wall. With a 50cms void (minimum for human access?), this is getting extremely tight....

    If it was infilled with blown glass, would this replicate the potential structural nature of the current soil infill?
  7.  
    Posted By: JulesSyes, public road. Very low traffic, but occasionally very heavy farm machinery etc.

    Is it a public road owned by the local authority or private land with a public right of way?

    Stone walls with rubble infill are not by any means classed as retaining walls capable of taking side thrust or pressure. AFAIK pressure through soil is calculated at an angle of 45 deg. so if you take a line the edge of the road at 45 deg. it is below this line that pressure from the road will affect the wall. Not only is it the pressure of the traffic but also the standing pressure of the soil. The loads on the wall will be worse if the road is bumpy as this will introduce additional vibration.

    Normally the loads from structures adjacent to a building are designed to pass below the foundations i.e. a 45 deg. line from the base of the structure should pass below the foundations of the building.I suspect that the road and the building have been there for some time, probably before the weights of today's vehicles were on the road. I would be concerned that the road and its traffic are now exerting an unacceptable side thrust on the wall of the building.

    If it were mine I would not be disturbing the soil between the road and the house until the SE has confirmed what is acceptable. Once the SE has commented on the structural stability of the whole situation then you may find your self talking to which ever authority has control of the road given that I suspect that the construction is nowhere near today's standards and I would be surprised if any insurance co. would entertain a claim in the event of movement in your wall.
    • CommentAuthorJulesS
    • CommentTimeDec 3rd 2023
     
    Hi Peter,

    Thanks very much, that's very useful information. It's a public road owned by the local authority.

    Regarding a SE, I think we're probably outside the expertise of the one we've been using for the building, is it civil engineers I need to be looking for? If anyone has any recommendations, I'd very much appreciate it (West Wales).

    Jules
    • CommentAuthorJulesS
    • CommentTimeDec 3rd 2023
     
    Also, we've done a 3D scan of the site (drone survey > model), and I've just been putting some angled planes into it and it does indeed hit the foundations - pretty much all along the road side. So would this mean (SE approval pending), any thing above this angled line is essentially fair game for removal?

    Many thanks,

    Jules
    • CommentAuthorphiledge
    • CommentTimeDec 3rd 2023
     
    This is just a guess, but I'd have thought the local authority would be responsible for structural support of their roads which would exclude using your building to support their road, unless you'd given consent and the house was designed that way. I'm guessing you haven't and it isnt

    Rather than you engaging and paying for a structural/civil engineer it might be worth contacting your local highways dept and explain that you want to clear out the void between the house and retaining wall due to damp ingress and ask them to confirm the road is adequately supported when not bearing on your house
    • CommentAuthorJulesS
    • CommentTimeDec 3rd 2023
     
    Hi Phil,

    Thanks, that's a good idea.

    I'd be interested to hear what people's opinions are in terms of 'is it best to involve the local authorities or not?'. I've spoken to a few people who have warned us off approaching the council unless legally required (general consensus of it slowing everything down and becoming very bureaucratic), I'd love to hear folks' opinions on this.

    Having said that, our personal experience of the council has been positive and we're open minded and want to do the best / safest thing so would just value others input on this.

    Jules
  12.  
    Posted By: JulesSRegarding a SE, I think we're probably outside the expertise of the one we've been using for the building, is it civil engineers I need to be looking for?

    Ask the SE you are currently using as they might know someone who has that expertise.

    Posted By: philedgeRather than you engaging and paying for a structural/civil engineer it might be worth contacting your local highways dept and explain that you want to clear out the void between the house and retaining wall due to damp ingress and ask them to confirm the road is adequately supported when not bearing on your house

    Now that's a good idea !!

    Cross posted with JulesS - If you are going to mess with the LA road in terms of removing support they have been relying upon for their road then you have to contact them.

    There are regs about supporting the sides of ditches in which you are working (elf an safety) to prevent the sides collapsing and crushing the workers. These will need t be followed if you are digging next to a LA road.
    •  
      CommentAuthordjh
    • CommentTimeDec 3rd 2023 edited
     
    Note that if Wales is the same as England it's not your local authority (as in District Council) but your County Council that is responsible for Highways. I would suggest contacting your local county councillor and seeing whether they can help. They need your vote to stay a councillor so they are motivated to help :) Ours attends our local parish council meetings (most times anyway) so that's a good place to introduce yourself.

    You mentioned there was some uncertainty about the land boundary. Is your plot not registered? If it is there shouldn't be much dispute. Who mows the verge of the road and who pays for it? And how wide do they mow?
  14.  
    Posted By: Peter_in_HungaryAFAIK pressure through soil is calculated at an angle of 45 deg.


    Posted By: JulesSSo would this mean (SE approval pending), any thing above this angled line is essentially fair game for removal?

    Not quite. 45 deg. is the typical. It will vary depending upon the soil type. E.g.disturbed soil or gravel will need a lower angle and rock can be steeper. So investigation will be needed before the safe angle can be decided upon.
    •  
      CommentAuthorfostertom
    • CommentTimeDec 4th 2023
     
    You say the 45o (or soil-type-appropriate angle) plane 'hits the foundations'. For static ground pressure + pressure from weight of vehicles that should be OK as long as the plane doesn't 'penetrate' the house interior but passes below interior floor level. However, yes if vehicles cause vibration that could have wider effects, don't know how to assess that.
  16.  
    Posted By: fostertomYou say the 45o (or soil-type-appropriate angle) plane 'hits the foundations'. For static ground pressure + pressure from weight of vehicles that should be OK as long as the plane doesn't 'penetrate' the house interior but passes below interior floor level. However, yes if vehicles cause vibration that could have wider effects, don't know how to assess that.

    But Jules said
    Posted By: JulesSBut it narrows significantly to a point where the road edge is about 90cms

    and looking at the diagram above with the ground level outside being a bit below ceiling level it seems unlikely that the 45 deg angle at this point would only hit the foundations and miss the wall.

    It looks a bit marginal at best so details are needed. And with a stone / rubble wall I wouldn't take any chances. Certainly if it narrows to 90cm and a 50cm trench is dug then this only leaves 40cm supporting the side of the road - IMO a recipe for trouble.
    •  
      CommentAuthordjh
    • CommentTimeDec 4th 2023
     
    I haven't managed to find any English docs, let alone Welsh ones, about excavating near a road. Though there's lots about excavating in a road! But I have managed to find one from Northern Ireland ( https://www.nidirect.gov.uk/publications/apply-excavate-near-road ) that says "If you want to make an application for consent to carry out excavations near a road you can use the application form below. As a guide, anything within 12 metres could be regarded as being near a road."

    Given the uncertainty about ownership, and about digging near a road, I would definitely suggest consulting either or both of a solicitor and your local county councillor.
    • CommentAuthorphiledge
    • CommentTimeDec 4th 2023
     
    Can't log in to quote anything so....

    In respect of LA involvement there's the remnants of a retaining wall that I'd guess was the LAs responsibility to maintain if its holding up the road?? Rather than ask if its OK to excavate and risk them saying no, I'd be tempted to tell them you're going to excavate regardless as you believe the road bearing on your property risks damaging it and the infill is causing damp.

    If you're not sure of the boundary it might be worth checking your deeds to make sure the retainng wall isn't yours and yours to maintain!!
    • CommentAuthorJeff B
    • CommentTimeDec 4th 2023
     
    What about using those steel sheet piles that are driven into the ground with a pile driver and then either pouring concrete into formwork or blockwork in front to create a retaining wall? Probably megabucks though I suspect, unless the LA can be persuaded to do it!
    •  
      CommentAuthorfostertom
    • CommentTimeDec 5th 2023
     
    I should think driving sheet piles so close wd shake the stonework badly!
  21.  
    If you are within a meter of the road I believe that you will need to involve the HA and may have to use their contractors. Thats on top of the 45 Deg issue mentioned above.

    Or don't tell them and get some gabions with EPS along the house.
  22.  
    Posted By: andrew_rigamontiOr don't tell them and get some gabions with EPS along the house.

    I would be concerned about the pressure on the stone/rubble wall with that approach.
    • CommentAuthorJulesS
    • CommentTimeDec 8th 2023
     
    Thanks everyone for your comments- really useful stuff. The diagram is misleading in so much as it's not to scale. The boundary is shortly going to be resolved based on land registry finally updating - it's only taken nearly 2 years. I'm planning on doing another drone survey in Feb, so will have a more accurate DEM of the site. It is sounding like we need to contact highways - do they have any power to just say 'no'?

    Thanks, Jules
    •  
      CommentAuthordjh
    • CommentTimeDec 8th 2023
     
    I'll just say again, I would suggest starting by talking to your county councillor and let them make the first enquiries of highways to establish the situation.
  25.  
    +1 djh. I've seen issues that likely would have received a flat NO, be taken on by the council without any fuss, after the local councillor asked questions.
    • CommentAuthorJulesS
    • CommentTime14 hours ago
     
    Thanks all for your help. We'll approach the local councillor and see how we go.

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