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Our neighbour is looking to add a rear extension to their adjoining semi, which will be set back 100mm from the boundary like our extension, and thus leave a gap 200mm wide x 4m long x ~2.5m high between the two extensions.
Ours is cavity wall block, rendered, with a gable end slate roof coming down to a gutter on each side. Their roof will be sloping the other way, single pitch. I presume they’ll be using some kind of block or brick that doesn’t need future maintenance.
I’m a bit concerned about future damp problems, especially if the render needs replacing because we won’t be able to access it.
They got permitted development agreed a couple of years ago when they did their loft conversion but nothing happened with the rear extension. Last week they came round with a party wall agreement saying the builder wants to start the week after this!
My wee concern will be how deep your foundations are and how deep his are going , easy to draw on paper the eccentric concrete foundation he will have to get a warrant but in reality he may undermine your concrete if your builder may have skimped when doing your extension
The found should be as deep as the existing house but sometimes they may have only went down 450mm ie just removed the topsoil
It's never a good thing extensions build on the boundaries like that unless done exactly same time and the neighbours get on
How do they seal the 200 mm gap as he can't roughcast his side, all the mortar droppings down the gap might cause a problem with bridging the gap
I have a friend who has an extension like this. Far from ideal. However it seems a bit harsh to say that they cannot have an extension up to the boundary because you got there first
We’re straight onto the chalk, below an inch or two of topsoil. The original house foundations (it’s from the ‘30s) are only a few bricks deep but we had to go down 800mm into the bedrock for the extension. They’ve got to bridge the same shared sewer that runs along the back so will be going to the same depth. Builder said they’ll dig by hand along the boundary so at to not disturb our foundations/walls.
My understanding is we can’t (and it would be wrong to) stop them but I’d like to do everything possible to minimise future problems.
Your neighbour should serve you with a Notice of Adjacent Excavation under the Party Wall Act. You can then appoint a surveyor to sort it out and ensure you are suitably protected.
We’ve had the party wall notice but I’m quite sceptical about most surveyors etc…
Just had a sketch through from the builder which actually seems a pretty decent solution:
I'd be a bit miffed about the short notice, it's pretty cheeky to want to start within days when you would be well within your rights to ask a surveyor's opinion. But at least the builder has attempted to address the issue of damp running off into the gap.
Is that existing guttering up to the extra load?
He's going to be jumping about on your roof to do the work above the gutter, I'm surprised a stronger fibreglass box gutter has not been specified by the architect, your plastic gutter and brackets might be aged and brittle
Very awkward to replace if in a few years it fails and needs replaced
Is that existing guttering up to the extra load?
Is it ever going to be possible to repair or replace the guttering?
I'm surprised a stronger fibreglass box gutter has not been specified by the architect,
Doesn't appear to be an architect involved here. But I'd agree with the need for something bombproof.
Looks to be receiving just what hits the vertical boarding side-on and runs off, so not sure it would be a vast extra load. Unless OP lives in Scotland.
Amazingly there is an architect involved. I spoke to him yesterday and his response was basically "it's not ideal but there's not a lot you can do to stop them"...
There will be a small amount of access between the houses to get to the guttering using crawl boards on our slate roof. I think the suggestion about replacing the rather flimsy existing guttering with something more substantial is good idea. We do have issues with there being a very strong wind tunnel between the houses down the shared drives, so if we're unlucky and get something similar in this narrow gap we could have winter storms pulling off a gutter that's very hard to fix back in place.
So if we have the guttering replaced with something with much larger lifespan, and the combination of lead flashing and new gutter can keep the side of the house dry, then the 20-30 year lifespan of the render shouldn't really matter. Does that sound logical?
I need to check how high the more waterproof outer course of blocks go on that side of the house - the other side of the house is uphill so I remember it went quite high to stop water on the drive getting into the house. I presume we should ensure that the space between the houses at ground level is shaped to act as a drain taking the water away from each wall and then out to the open space at the end.
Would some kind of mesh across the open end to stop anything like leaves/bird/animals getting into the space but allowing airflow be sensible?
We live on a hill on the south east coast of England - I haven't been to Scotland for quite a while but I don't think our weather is quite as wet but it's not exactly dry and recent winters have been very stormy.
I'd want a box gutter sitting on strong brackets or corbelled brickwork so it's fully supported and rather than leave a 200 mm gap between the buildings built up close with a 1/2" mastic joint almost like an expansion joint with slip ties to give it strength so you can keep vermin out that 200mm gap. It could easily be vented with slim vents every 450 vertical
Next door would have had to get drawings passed for pp and BC so why has the architect/technician not detailed this part? Rather than the builder does what suits him
Think 5 years ahead and next door neighbour has moved on but you're still there with new neighbours nothing to do with the extension build and there's a leak appeared and a damp patch
The architect/builder/engineer no one will accept blame
my house is built like this. the previous owners and next door didnt get along. It hasnt caused any issues that ive noticed, though roofing the extension was a fiddle.
If they are digging anywhere near your foundations, they need a party wall notice*
They need to formally inform you
you need to formally agree to the work
just covering both your arses should your house start to move.
* - even if you dont NEED one, its a good idea to have in place?
https://www.gov.uk/party-walls-building-works
the builders sketch looks good, not just because theyve got a plan, but theyve drawn a neat and clear sketch. They know what theyre planning, and it suggests they know what they are doing in general. Youd be lucky to get a scrawl sketch from some builders
Think 5 years ahead and next door neighbour has moved on but you're still there with new neighbours nothing to do with the extension build and there's a leak appeared and a damp patch
can you get in now, and paint the whole wall with good quality masonry paint, as a belt and braces (or get them to do it)
I wanted to build out to my boundary but builder warned me it's v expensive as any foundations have to protect my neighbour, ie, any issue I cause to him is my cost to fix. Luckily I m detached so for the sake of 3 feet I decided it wasn't worth it.
Neighbour on other side built to boundary and can only access their gutter from above, not ideal, I jetwash it as it's north facing and gets mouldy.
The structural engineer did explain to me what was needed to build to boundary, I d say half the refurbs have done this, half have retained side access. Our problem is a 2 meter drop to neighbouring plot, it was going to get expensive as the drains run alongside, but within, my boundary.
The builder highlighted a crack all the way up the middle of our render on that wall and he's offered to re-render that FOC and if it proves to be a crack in the actual blockwork he said he'll also insert steel ties to stabilise the wall before re-rendering. He seems quite a reasonable chap. I think we just need to agree a really durable guttering solution. If their wall is block can they add corbelled brick? Or will the exposed tops of the brick create a potential entry point for damp on their side?
I agree about the architects drawings - surely they must have designed the new wall to take into account it can't be rendered? And as part of that they should have detailed the solution for our wall. I'll ask the builder what detailed drawings the architect provided, if any.
When the same neighbours added a loft conversion which is built onto our loft conversion they agreed to add extra soundproofing at their cost (which was totally needed because before it was added I could hear the builders' conversations/radio from our bedroom), so I'm sure they'll be flexible. With the party wall agreement for the loft I added a load of stuff about what we required from them to get our assent.
Couple of thoughts, future maintenance and who repairs the gutter, is it 50/50 cost and agreed in writing (imagine in 10 years who remembers what was agreed!), also is building regs passed, appreciate it is their work and not yours but worth asking... with the party wall act PWA, from memory BEFORE work starts get the party wall surveyor* to record your property, so any future issues are recorded, i.e. if they undermine foundations and your wall breaks the photos and survey will shown your wall in good condition, so the PWA also protects you.
* if they don't appoint one you can get your own and they pay, so worth a chat with neighbours as you also want to maintain relationships.
This has always seemed quite silly to me that when building an extenstion you have to leave the boundary gap.
I agree! Especially as the opposite happened with our loft conversions!
This has always seemed quite silly to me that when building an extenstion you have to leave the boundary gap.
You don't have to have a gap. If both sides agree it can be built straddling the boundary, so it would be a "party wall". Obviously can't be done in the OP's case (unless they are prepared to demolish their own extension).
I would be using a much more substantial guttering system, no way would I be using the existing in that situation. Something along the lines redmex is talking about with no joints ideally and capable of handling significant future rainfall.
A lot of existing guttering systems aren't sufficient for the deluges we can experience now, let alone in the future
Ime people are incredibly blase about the effectiveness and water tightness of their guttering, yes you may get away with it in a conventional situation but in this instance you are creating potential problems. Throw in a bit of moss and a few leaves, you've got overflowing gutters and standing water in no time. What happens in a typical UK winter where a few inches of snow falls, then rapidly melts - the gutter will fill with slush, the melt can't get out and just tops the guttering and goes between the properties.
If you spend any time at all working on roof/guttering/lead work you will know that fast running water off a roof is quite something to see. Details matter, and if you get it wrong the water is firing up and bouncing off in all directions and down the walls.
In addition I would be wanting some sort of draining at the base of the gap - that way any water that managed to pass the guttering isn't going to soak the ground. If you are careful you may be able to install something that could be kept clean. A French drain perhaps or channel system. Make sure it's covered temporarily while blockwork is done, you don't want it filled up with mortar that's dropping out the back of the new wall as it goes up.
Think I might consider getting the heavy duty guttering attached to their house, with your roof draining into it. Makes future maintenance their problem.