waterproofing a barn built into the hillside

[Catherine Davis]

We have been pondering on how to tackle the problem of keeping the barn dry (to make it habitable) The back wall is built into the hillside, a small road runs behind it about 1.5m above floor level. The hillside is clay and during the winter or in wet periods water seeps through the walls and spreads over the barn floor. We have discounted digging a deep trench behind the wall, as the road is in constant use and it might cause a collapse. Latest idea is to dig a channel around the inside base of the walls, erect an inner wall and fill the space between with gravel to allow the water to seep through and then flow along the channel and we'll drill a hole for a pipe through the wall each down hill end of the barn, and lay a pipe to a soakaway. Would this work?

[Harry Bloomfield]

It happens that Catherine Davis formulated :

Something similar....

Floor was good solid concrete and some 3x3 galv angle iron was bolted down to a sealant on the the floor, all the way around the wall edges leaving a gap between angle and wall. The water ran to a sump, from where it was pumped out. Filling a channel with gravel, could mean the gravel might tend to choke up with sediment.

[Owain]

Up to a point. You would need to waterproof the inner wall (and floor) with a tanking membrane, basically treating it as a cellar.

If you are going for Building Regs approval you'll probably need to demonstrate the road is adequately supported anyway.

Owain

[JimK]

Should do - sounds exactly like my house... are you thinking of making an offer :>)))

ours has a block interior wall creating a large cavity wall if you will (you can get in it at a squeeze) at GF level. At it's base is a formed concrete channel (below the "working" concrete floor (& DPM) level in the rest of the GF) Excess water that permeates thru is collected and drains away along the channel into a convenient drain thence out to a soakaway.

One possible snag is how to effectively "tank" the exterior face of the new interior block wall (if you see what I mean) - If space is tight (how big is the barn and can you spare the space for blockwall and cavity?) how will you tank it effectively? Suppose a "curtain" of thick polythene dangling from the top of the new inner wall could direct any more severe water penetration down into the channel but in say a narrow cavity how will you ensure it is straight /gets to the vertcial level where it will be needed......

In any case I wouldn't fill such a cavity with anything otherwise you may find it bungs up in the future....or bridges damp across from day one...

Cheers JimK

[js.b1]

I would have thought tanking is better.

Apply tanking sheet to the wall & floor. Tanking sheet is a thick plastic sheet with deep dimples which raise the sheet off the wall. It is fixed by plastic plugs with integral seals so as to not create a point of weakness re damp penetration.

Pump is fitted. Pump is fitted at the lowest point with a float switch which pumps away water as necessary.

I'm not sure how you fit them to rough wall surfaces.

I assume this is not living (sleeping) accommodation because BR apply and they can be onerous - like is the barn wall that backs onto the road properly supported, re foundations and capable of withstanding the road. Underpinning is an exercise in mixing a lot of bags of concrete to fill a block a few feet wide at a time (some builders prefer to dig the trench in one go - and promptly fill it with the original building... just imagine if programmers did Civ Eng... Now why did it do that... :-)

[JimK]

yes another possible method - should be lots on uk.diy if messrs Google's search is operational....

has some stuff but I've never used it and can't recommend.

how far can BCOs "insist" -after all it's existant i.e. it *is* already potentially holding the road up and we are talking of creating a drier area inside of it without necessarily touching it..??

JimK

[Catherine Davis]

[Catherine Davis]

Thanks for the reply. what gap would you recommend? I don't think I'd need to waterproof the exterior of the inner wall, it is a very slow trickle even on the wettest days, hopefully the water would run down the inside of the exterior wall, into the channel and through the wall via a pipe to the soakaway

[Owain]

"hopefully" is all very well but if you're spending money on this I'd be looking for some insurance-backed guarantees.

And if the pipe to the soakaway gets blocked, it doesn't take much water to create a lot of hydrostatic pressure and down comes the wall.

Owain

[george [dicegeorge]]

how would you clear it if a dead rat blocked it? a jet of water?

[g]

[JimK]

10,000,000 Euro question... do youmake it big enough to squeeze into if the worst should happen or as small as poss to save interior space (a la membrane tanking described earlier)?

NB we've never had a dead rat in ours - why would they be interested? no food, no warm habitat? nah you'll be alright in that regard I reckon- make the drain a big 4" interceptor "U bend" jobby and it'll take a lot to bung it up, access to the drain would be an advantage for worst case scenarios tho... you don;t want to be ripping whole (wet) walls down to unblock drains.....

JimK

[js.b1]

What condition is the barn in, and size?

Existing:

- You have a rear wall which is leaking, tight against road, supporting said road to 1.5m into the ground.

Solution-1:

- You tank, drain, line whatever the barn

Solution-2:

- Abandon the rear wall as a road-supporting wet wall

- Remove 1m of the sides against that rear wall

- Remove the roof

- Rebuild 1m of new sides at the front wall

- Refit the roof

By remove & rebuild I mean just that - you re-use everything except new mortar & new roofing nails n sarking felt.

It depends on what condition the barn is in re roof, walls, foundations etc. Some barns as you probably know are built directly onto the ground - any concrete being a poured floor within that area for cows, or whatever :-) Some barns are little better than random pile of rubble with corrugated iron roof complete with more ventilation holes than the night sky has stars.

Just consider every option - even the seeming most extreme.

[The Natural Philosopher]

Probably not.

What you need to do is simple. Build an inner shell that IS waterproofed, and insulated against the earth soil and water.

So you might tank the wall and floor with waterproof mortar or DPM, or probably both , and then build an inner leaf wall BEHIND the DPM and fill the gap with insulation. And lay down insulation and build a new floor.

[The Natural Philosopher]

I think they can, in the ultimate analsyis , declare it as unfit, or unsafe for human habitation. Or Elfin safety can.

Wasnt there a case of a cottage lived in for years, with water fed from a stream and no electricity and no mains drainage? then something triggered the authorities, and they told the occupant that they couldn't live there as it wasnt fit for inhabitation, despite it having been that way for 35 years or something?

[Owain]

Environmental Health can condemn as unfit for habitation Building Control can condemn as structurally unsafe

(AIAUI)

private water - okay if tested and shown to be potable private drains - okay if meets environment regulations no electricity - private supply or gas lighting okay. Current building regs require fixed lighting and heating installation, but AIUI plumbed- in gas lighting still meets that requirement.

Owain

[Catherine Davis]

Thanks Jim I think I understand a bit better about the membrane, ie it's structured so water flows down behind it. I would need a block wall though, because I need it to support a mezzanine floor and the joists running the width of the barn might be too long. I could perhaps put a hatch in somewhere in the interior wall to enable inspection, for rats, collapse etc

[JimK]

but current Bregs apply in the main to *new* dwellings? they couldn;t seriously retrospectively force some old hermit in a croft on shetland (or local equivalent) to "as of now" install all that instead of a peat fire and tilly lanterns - could they? on what basis?

JimK

[JimK]

yes we have a "hatch" affair to get in our "cavity" near the exit drain (that also takes the kitchen sink, dishwasher, wash machine etc) Never had an issue with it yet apart from woodworm in the hatch! (all this built before my time here)....

Suppose you could look at the best of both worlds - membrane idea for most of the width of the wall leading ingress down to a (below DPC level) gully with a fall across to a drain. Where the drain is located, make the cavity bigger so you could get in with a rod or two if the worst happens??

JimK

[Catherine Davis]

Barn is 7m * 5m. It is 200 years old. There is a 2m wall above road level, supported by the clay hillside. We have replaced the roof tiles and rotten rafters added gutters and the roof is now watertight. I want to keep as much floor area as possible. Need an inner block wall to support a mezzanine. My father is helping with the engineering and plans, but he is nearly 90 and not very up to date with new methods, but has a vested interest as he will live in it. I think the concrete is laid on the ground..our nearby house has no foundations and floor tiles laid on the ground with very little in between, but apart from the glaze coming off the newer tiles it isn't a problem. I will put the block interior wall on the existing concrete floor. Is this sensible? It will support the joists holding up the mezzanine. It is a barn worth doing something with as unlike most of the barns in the area which are constructed of sun baked mud bricks, and half collapsed, the lateral walls of this one are 60m and have a high proportion of stone, which is why, like the house, it is still standing.

[Catherine Davis]

Here in France the rules are very strict for new work done, all building works done by a registered builder carry a 10 year guarantee, but there is no interest taken in living conditions in old houses, there is still no legal requirement to have a septic tank!... (but we have one)