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    • CommentAuthorjemhayward
    • CommentTimeMar 23rd 2018
     
    We bought our grade 2 listed thatched mediaeval hall house in 2005, and some years later a neighbour mentioned that we had a cellar. We could see no evidence of this, either inside or out, but I managed to contact the previous owner's daughter, and she recalled her father telling her that he could either keep the cellar or install a downstairs toilet (he was elderly) - though as she was living in the USA at the time (1977) so she'd not seen the house before her father renovated it.
    So, we were wondering if we had a cellar, and whether it was dry (we live at the bottom of 'Watery Lane'), or if it was filled in as the kitchen had a concrete screed floor, so maybe they'd filled the cellar with rubble from the outbuildings that had been demolished at the same sort of time.
    Time went on, then just after xmas we noticed the floor of the downstairs toilet was wet, and eventually discovered that our lead mains water pipe had started leaking inside the wall. We couldn't cut off the mains water as it served six of our neighbours as well, so we had to put up with the slow leak, but noticed that the water wasn't building up, it was draining into the floor. Leaking pipe was fixed, and builders have come in to assess the damage for the insurers. They took out the loo, broke up the floor and found soil and rubble below, but remarkably little wetness. They advised us to just let it dry out, but we decided to remove some of the rubble, and found a staircase leading down to a breezeblock wall. Builders came back yesterday, as we are now thinking that the water has travelled down the steps, and took out the wall. the steps went down yet further into a largely dry, stone vaulted cellar the size of our kitchen. At the front there is a partly bricked stone mullioned up window, which is now well below the front garden, and soil and water have come through, leaving about 2" of water on the flagstone floor. The ceiling height is just 6ft in the centre, so not an easy room to live in. We will have to remove the flagstones to let the floor dry out, and we will be digging a light well in the front garden to let light in through the window, but keep out soil and water.
    What we are thinking is that if we dig down say 3ft, we could install a radon barrier (a good idea where we are) some insulation, and maybe underfloor heating (we have a AS heat pump).
    Questions: will the listed buildings people let us do that?
    If we dig down that far will we expose the bottom of the walls?
    If we do, will it all collapse?
    What do we need to do to maintain the structural integrity?
    Should we look at tanking the lower section?
    Do we need a sump and pump in case we get water coming up?

    Anyone with any experience they could share?
    •  
      CommentAuthorfostertom
    • CommentTimeMar 23rd 2018 edited
     
    What a thrill!

    I had a basement, same size as whole original Riverside Cottage which quite often flooded above GrdFl level. We did new RC cellar floor keyed into the walls, incl central sump, all Vandex tanked to 3ft above GrdFl, thus creating a 9ft high bath tub. With over 100 tonnes potential buoyancy uplift, we had to check that the weight of the stone rubble built house was great enough to prevent the whole thing floating! And that the new ground floor joisting would brace it from collapsing inward - as well as that the downweight + inward force would still resolve within the middle third of the wall thickness.

    In 17yrs it only once just came over front door theshold, at Xmas while away, so didn't have the doorway shutters up, but the cellar pump just about kept pace. The Vandex render hardly leaked, didn't blow off the wall despite 2.5tonne/m2 inward pressure. Later sold it, and it flooded 2ft deep twice in next 2yrs!

    It was dry enough for storage but always a bit humid - nowadays I'd have fixed that. I now suspect that mould down there below my every day office space kept me feeling a bit off-colour, sleepy, for all those years. Not to mention the trunk pylon line 60m away!
    • CommentAuthorjemhayward
    • CommentTimeMar 23rd 2018
     
    By the looks of the walls, I don't think the cellar is prone to flooding, and the water in there at the moment is probably water that has run in from above, and isn't draining away. We could only realistically tank the section we dig down below existing floor level, as we'd want to preserve the original stone walls for aesthetic reasons. So, if we had a 3ft high bathtub, the forces would be more manageable in a flood scenario?
    •  
      CommentAuthorfostertom
    • CommentTimeMar 23rd 2018 edited
     
    I later discovered Polybond 19 clear, which was reasonably effective at cellar tanking, leaving the stone visible if semi-gloss. The wall had to be perfectly pointed in fair depth - none of the soft earthy mortar often used in old rubble built cellars. And bone dry for several days while the 3 (I think) coats dried. Absolutely 100% dibble-coating into all crevice surfaces - slow work. Absolutely no penetration by later fixings - there wd be considerable hydrostatic pressure behind the coating just waiting to squirt out.
  1.  
    Well done.

    I am hoping for the same result in our Listed Building when we lift the stone flags to put the UFH in which we then have to relay. I dont think you will have a problem with Listed Building so long as you had permission in the first place to take out the loo and rip up the floors. If no permission then go with your begging bowl and explain the circumstances whilst asking for forgiveness. Once back up off your knees explain that its an original feature of the house which you would like to retain and restore to its former glory using traditional materials ie lime mortars and plasters retaining the flag floors but with UFH below the flag floors and a limecrete construction using foamed glass. Would also suggest installing a Lunos type MHVR system which gave us extra Listed Building brownie points as it is perceived to protect the fabric of the building by regulating humidity. Your quite welcome to quote our Listed Building Consent which has all this approved but we did have to fight for it with the help of English Heritage. I would think you will need to do a full Listed Building Consent application which will need to include a heritage statement outlining the history of the building which we found fascinating doing some of the research.
  2.  
    Unlike Fostertom I would not initially tank as I have found old properties really dry out well if they are allowed to breath. Normally on cellars they have a french drain system which keeps them dry. Over time the french drain gets contaminated with soil and stops working. Just a simple replacement of this french drain material with foamed glass not only restores the porous nature of the french drain but also provides further insulation.
    • CommentAuthorCWatters
    • CommentTimeMar 23rd 2018 edited
     
    Questions: will the listed buildings people let us do that?
    If we dig down that far will we expose the bottom of the walls?
    If we do, will it all collapse?
    What do we need to do to maintain the structural integrity?
    Should we look at tanking the lower section?
    Do we need a sump and pump in case we get water coming up?


    I would find the deepest part of the water and lift a flagstone and dig a small hole to use as a temporary sump. Pump all the water out with a cheap or rented submersible pump (don't let the pump run dry or it will die).

    Then wait a few days to see if the water comes back and how fast. See if you can figure out where it's coming from.

    Then dig one or two small holes near the walls to see how deep the foundations are. Depending on what you find it might be easy or prohibitively expensive to do what you want. If the foundations are deep enough all well and good. If not then some sort of under pinning is likely to be required, perhaps making it all too expensive?

    Apart from the small test holes you certainly shouldn't dig lower than the foundations over a larger area without proper advice. You would indeed risk structural problems.

    One option would be to show your trial holes to an SE and ask him to propose a solution for under pinning. Alternatively find a basement conversion specialist who knows how to do under pinning. If you were thinking of doing all the digging yourself or unsure about the company get your SE to write a "method statement" for the under pinning. Your BCO might want to see one anyway. Perhaps even have the SE supervise the work. Typically this would involve propping and digging out short sections say 1 meter long every 3 meters. When those have been filled you go back and do more 1m long sections. Rebar is pushed into the ground so the sections are joined together when the concrete is poured.

    Probably the best but most expensive solution for tanking involves lining the walls with an egg box like waterproof material that allows water to drain down into a channel around the bottom of the walls. From there it gets pumped out or if you are lucky with the terrain (eg house cut into a hill) you can run it out through a wall and away.

    But that's getting ahead of yourself. See what happens when the water is pumped out first.
    • CommentAuthorjemhayward
    • CommentTimeMar 23rd 2018
     
    The listed building people allow 'investigation' work to be carried out and they won't care about the 1970's toilet and concrete floor.
    The house itself has MHRV already, but there is no practical way of extending it to the cellar.
    The house is essentially damp already, it has no DPC, of course, and is buried about 90cm into the ground at the end with the cellar, so there is constant damp soil on the other side of the walls, but they are about 1m thick in places. We just let it breathe and its not a problem.
    The actual cellar walls are dry, and clean so I doubt if water is trying to get in sideways, but I fear that when we go down, we will possibly encounter wet soil.
    My thinking is radon/dpc on the soil, then insulation, UFH, lime screed, with the original flags set into that. My plumber is confident that the UFH will be fine with the flagstones, though obviously not offering 'instant' heat.
    • CommentAuthorrevor
    • CommentTimeMar 23rd 2018
     
    I have no experience of this situation but noticed that you were thinking of a Radon barrier. It might be useful to get a measurement kit for radon. Basically it is a couple of cards with a detector of sorts which you expose to the room environment. Usually one upstairs in a bedroom and another in a living room. Leave for 3 months and send them off for analysis and within a few days you will get a report. We live in a Radon area but it is very variable and we did the analysis before we embarked on our renovation. Can't remember where we got it from but I am sure if you google it you will be able to source it. From memory the kit was about £40 but that was 10 yrs ago. As we were well below the action level we did not have to do any radon protection. Could save you work and you will know what you are dealing with. Even if you need to take some protection with having a basement a ventilation system in there may be all that is required
  3.  
  4.  
    I was advised to use compacted foamed glass as the insulation layer as normal foam insulation would buckle under the weight of the stone flags. Reusing the stone flags is part of our UFH listed building consent.
  5.  
    wot CWatters said above about pumping out. Over here you can get cheap (50 - 100 GBP) submersible pumps with float switches built in to stop dry running. Once pumped out you can see any refill. I would then decide the long term use for the (wonderful) find. A vaulted ceiling with 6ft headroom limits its usefulness. The eventual use will guide what renovation/alteration/expense you do. Is the bricked up window actually a window or is there any chance that it is an external entrance? Over here such a cellar would either be a wine cellar or for root veg. storage.

    I would be cautious about lifting the flags as something has to be holding the walls apart and if the walls do not extend much below the flags then lifting them might allow the walls to move inwards heaving up the floor. Again with experience from over here I would suggest that the stone walls have either earth and rubble infill or at best some lime thrown in if the original builders were feeling extravagant. Such a wall can be washed out by the inflow of water so caution would be needed.
    •  
      CommentAuthorfostertom
    • CommentTimeMar 24th 2018 edited
     
    Posted By: renewablejohnUnlike Fostertom I would not initially tank as I have found old properties really dry out well if they are allowed to breath
    Quite agree - try that first. In my case there was abs no doubt that water level in the cellar (basement actually - no vaulted top, just GrdFl joists) faithfully followed nearby river level.

    Posted By: Peter_in_HungaryI would be cautious about lifting the flags as something has to be holding the walls apart and if the walls do not extend much below the flags then lifting them might allow the walls to move inwards heaving up the floor. Again with experience from over here I would suggest that the stone walls have either earth and rubble infill or at best some lime thrown in if the original builders were feeling extravagant. Such a wall can be washed out by the inflow of water so caution would be needed.
    All true - if surrounding ground is even partly waterlogged (as distinct from merely wet) inward pressure will be considerable - 1 tonne/m2 for every m depth of waterlogging - so bottom of wall can kick inward if dug downward esp if right down to base of wall - it can become free to slide on its bearing.
    •  
      CommentAuthordjh
    • CommentTimeMar 24th 2018 edited
     
    Posted By: renewablejohnI was advised to use compacted foamed glass as the insulation layer as normal foam insulation would buckle under the weight of the stone flags. Reusing the stone flags is part of our UFH listed building consent.

    Sounds like BS to me. We have normal foam insulation supporting a concrete raft and an entire house! Though to be fair, the foam under the walls is EPS250 rather then the EPS70 elsewhere. Not that there's anything wrong with the foamglass as long as there's a rigid layer on top to keep them level.
  6.  
    Posted By: djh
    Posted By: renewablejohnI was advised to use compacted foamed glass as the insulation layer as normal foam insulation would buckle under the weight of the stone flags. Reusing the stone flags is part of our UFH listed building consent.

    Sounds like BS to me. We have normal foam insulation supporting a concrete raft and an entire house! Though to be fair, the foam under the walls is EPS250 rather then the EPS70 elsewhere. Not that there's anything wrong with the foamglass as long as there's a rigid layer on top to keep them level.


    Did not have any choice in the end as LBO accepted the LABC approved system.
    •  
      CommentAuthordjh
    • CommentTimeMar 24th 2018
     
    Posted By: renewablejohnDid not have any choice in the end as LBO accepted the LABC approved system.

    Yeah, sorry, no criticism of you intended, it's the advice and advisor I'm questioning.
    • CommentAuthorjemhayward
    • CommentTimeMar 30th 2018
     
    <blockquote>I would be cautious about lifting the flags as something has to be holding the walls apart and if the walls do not extend much below the flags then lifting them might allow the walls to move inwards heaving up the floor. Again with experience from over here I would suggest that the stone walls have either earth and rubble infill or at best some lime thrown in if the original builders were feeling extravagant. Such a wall can be washed out by the inflow of water so caution would be needed.</blockquote>

    I think the term flagstone may be a bit of an exaggeration, what we have is a collection of stones on the floor with very variable gaps between them, and some semblance of flatness, so I doubt they are offering any structural support.

    Unfortunately my local conservation officer has left, and I don't know the new one, and they don't know the house, so I'm going to have to tread carefully.
    • CommentAuthorjemhayward
    • CommentTimeMar 31st 2018
     
    And now for a complete re-think!
    This morning we woke to an indoor swimming pool, though only 25cm deep. So, yesterday's rain has got in, from somewhere, and maybe the water table has risen, or its come in through the buried window (some of it came in that route, but probably not all of it).
    The floor slopes towards the front of the house, and we think we may have found a drain hole, but it's pretty much blocked, so we're just waiting to see where the water goes, and how fast. However, I think that we may have to abandon any idea of lowering floor level, insulation, underfloor heating and so on, and look at improving the drainage, and keeping as much water out as we can, but I doubt we will get it completely permanently dry.
    • CommentAuthorgyrogear
    • CommentTimeMar 31st 2018 edited
     
    Posted By: jemhaywardI doubt we will get it completely permanently dry


    Earth & soil is rarely "completely permanently dry", even in the desert !
    Not sure it would be a good thing, even ! especially if you are sited on clay, for example...

    gg
  7.  
    Posted By: jemhaywardAnd now for a complete re-think!
    This morning we woke to an indoor swimming pool, though only 25cm deep. So, yesterday's rain has got in, from somewhere, and maybe the water table has risen, or its come in through the buried window (some of it came in that route, but probably not all of it).
    The floor slopes towards the front of the house, and we think we may have found a drain hole, but it's pretty much blocked, so we're just waiting to see where the water goes, and how fast. However, I think that we may have to abandon any idea of lowering floor level, insulation, underfloor heating and so on, and look at improving the drainage, and keeping as much water out as we can, but I doubt we will get it completely permanently dry.

    With 25cm of water from yesterdays rain I would doubt that the water table would rise that quickly, rather that rain water is flowing in from somewhere and as you speculate the window sounds a prime candidate. And that volume of water sounds like the roof (or hard standing or concrete path) is collecting the rain which then makes its way into the cellar. (Of course it depends how much rain fell yesterday, biblical proportions or gentle spring rain?).

    Do you have any gutters on the house? and do any down pipes take rain well away from the house?

    Hopefully the water is coming in through the window, if it is coming through the wall(s) then IMO this could be serious as water will wash out the wall internals threatening its structural stability
    • CommentAuthorjemhayward
    • CommentTimeMar 31st 2018
     
    We're thatched, so the run off from the roof falls into the garden, about 20cm out from the wall, so will tend to percolate down the outside of the walls. The back wall is wet, but that is the wall that had the leaking pipe in it, so we expect it to be so, and at the back of the house the garden (which is not ours!) comes up to the ground floor windowsill, so the bottom of the cellar wall is over 3m underground. There is evidence that some water has come in through the window, but it's hard to imagine that amount of water coming in that way, but it may be as a dripping tap can fill the sink pretty quickly! There was a huge amount of rain yesterday, and lots of flooded fields locally, so the amount of rain we had was about as much as we could normally expect in a day.

    I suspect the cellar has been flooding like this regularly for at least 40 years, possibly more, so if it was going to seriously threaten the integrity of the walls it would have done so by now.
    • CommentAuthorArtiglio
    • CommentTimeMar 31st 2018
     
    Sort of similar situation, my parents moved to midwales in 1987, the farmhouse dated from mid 1750’s. Cellar floor similar to th op’s, random slate slabs with gaps filled with pebbles. Whilst its been generally dry through their ownership. They got to know an old girl in the village who’d been born in the house and remebered as a child the cellar regularly flooding to cover the bottom step. They also drew their water from a well in front of the house. At some point the fields locally had drainage ditches dug , whereafter the well dried up and cellar never flooded again. The plot the house is on is bounded on 3 sides by a raised “berm” about 2 feet, wether this was to protect from historical flooding or a result of field boundaries nobody knows.
    When the house was refurbished ventilation ducts were run from the cellar to thefireplace in the lounge to provide for the woodstove. Wether this has led to any meaningful airflow in cellar helping keep it dry, i’ve no idea but it cannot have hurt.
    • CommentAuthorgyrogear
    • CommentTimeMar 31st 2018
     
    I suspect we are starting to understand why the OP's cellar was finally filled in !

    One (somewhat radical) solution to keep it dry might be to pressurize it with air.

    (In the same way that an electrical plant room might be fitted with emergency CO2 pressurization, to keep the water out in event of flooding).

    gg
    • CommentAuthorjemhayward
    • CommentTimeApr 11th 2018
     
    Update: The water has now been all pumped out, and no significant extra water has appeared despite the rain. We've spoken to our Conservation Officer, and they are happy for us to do the repairs to the lintels, open up the access, lift the flags from the floor and install a drainage membrane at least, and put in a sump for the pumps(s).

    Most cellar sump systems seem to assume that they know where the water is coming from, and are basically a large (expensive) plastic bucket, sunk in the ground. If you suspect water is coming up from below, you also drill holes in your bucket. For some reason I'm not that keen on installing a large plastic thing in my 500yr old cellar, so I was wondering if we could just dig a hole and line it with stone / brick which we have loads of on site, maybe with a geotextile membrane outside of the stone to keep silt out and maybe a paving slab on the bottom to provide a flat base for the pumps.

    Could we also use this void as our radon sump, if we fitted a vent pipe near to the upper lip of the stone 'box'?
    • CommentAuthorArtiglio
    • CommentTimeApr 11th 2018
     
    I’d be very cautious until you’ve definitely worked out where the water comes in and how fast it does so. From what you’ve written structurally everything has held up well for 500 years. Be a shame to upset the buildings “equilibrium “ trying to get things sorted quickly. The water has been getting in and out without causing any real damage to date.
    I’d be tempted to tackle the other things you mention but leave the floor and any pump system until the water ingress is fully identified, which could well mean monitoring it for a full year or more. Maybe worth putting in permanent lighting and a camera tacking an image every hour or linked to moisture sensors on the floor (at lowest points”

    I’ve no experience regarding radon.
    • CommentAuthorjemhayward
    • CommentTimeApr 11th 2018
     
    <blockquote><cite>Posted By: Artiglio</cite>The water has been getting in and out without causing any real damage to date.</blockquote>

    Actually, that isn't true, there are two niches in the side walls that have no lintels at all, but we have found what may have been them nearby. There were lintels across the front 'window' holding up the kitchen floor, but they now look like thin pieces of veneer, and are holding up nothing. There is a beam in the ceiling arch that has rotted completely and part of the arch is collapsing as a result, so we definitely need to reduce the water ingress urgently.
    Some comes in through the front window/coal chute, as that is now 1m below the garden, and we can see soil and roots. An lot is coming in through the rear wall, as there is no management of the run off water from the rear garden that slopes towards the back wall. Some may just come up from below, and the drain at the front doesn't work, so we have a pretty good idea where it's coming from, and where it's not going to.
    •  
      CommentAuthordjh
    • CommentTimeApr 11th 2018
     
    I have a feeling a few simple line drawings might help people visualise the situation.
    • CommentAuthorjemhayward
    • CommentTimeApr 11th 2018
     
    <blockquote><cite>Posted By: djh</cite>I have a feeling a few simple line drawings might help people visualise the situation.</blockquote>
    Good point - I'll scan what I've done later today and post - I'm not a draughtsman!
    • CommentAuthorgyrogear
    • CommentTimeApr 11th 2018 edited
     
    @Jemhayward

    Hi, You have made a couple of references to the front garden being "high",

    ("which is now well below the front garden") and a reference to the back garden (neighbour's...) sloping towards your back wall...

    Any chance you could "plot" these events in time, to determine when (and why ?) this overburdening has occurred

    (unstated aim: "find a guilty party to sue")

    and determining what would be the chances of reversing the situation (by excavating).

    As I see it, it sounds like the original house was partly buried at the rear (or alternatively, *has become* partly buried because of landfilling by back neighbour etc.)

    and the front garden idem (? for what reasons ?)

    In any event, it sounds like the house surrounds have been gradually buried over the years, to the point that any surface drainage that existed previously has not only ceased to function, but that extra runoff is occurring on top of it, creating the "solid sponge effect" known to hydrogeologists (and cavers...)

    and that at some point the cellar started flooding (because of it), to the point where sb decided to fill it in to avoid the hassle of it all.

    Now one comes along and wants to correct it with pumps and drains etc.

    On balance, to me the layman, this looks not only costly but unfeasible.

    If on balance with unlimited budget you managed to drive a one-meter steel tube right into the cellar underfloor, from approximately 20 meters away from your front wall, then you just might manage to drain the cellar..

    ... but the latter then might fill up from the rest of the (uphill) gardens etc. behind your house... You could end up draining an entire parcel of neighbour's land going miles uphill of your property !

    (I have seen such an example performed on a Swiss hotel that was threatened by a moraine lake - I can't remember who paid for the job).

    gg
    • CommentAuthorArtiglio
    • CommentTimeApr 11th 2018
     
    I don’t disagree at all regarding the replacement of lintels and repair to the arch, but i’ve great faith in old buildings as such, i’d do those repairs using some decent rot resistant timber , and repair the arch.
    But deal with the water ingress along the lines of gyrogears post, and if wholesale reduction of ground levels is impractical, then something along the lines of trenches on the outside of the affected walls , drainage membranes/sheets against the wall and backfilled with gravel/stone/shell to provide drainage.
    More a deal with the cause rather than symptom approach.
   
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