Terraced house design question (OT)

[John]

I noticed that in some cities - especially London - terraced houses have the party wall extending above the tiled roof. In other places the party wall is entirely internal.

Why the variation?

[John Williamson]

Different local rules. London's been slightly paranoid about fires spreading rapidly since 1666.

[Nightjar]

Actually, it has been since 1212, when thatched roofs were banned.

However, as you say, rules were introduced for the City of London in

1667, requiring all houses to be of brick or stone, with heights carefully specified according to location. Dividing walls carried above the roof line and a minimum width for streets were both attempts to create fire breaks.

The City of London rules were extended to Westminster four decades later and an Act of 1774 introduced them to the entire built up area of London, adding things like windows and doors having to be recessed by at least 4 inches.

Most other cities took their lead from London particularly if, like Warwick they had their own great fires.

Colin Bignell

[dennis]

So paranoid that they didn't even bother building the party walls up to the roof until a few decades ago.

[Dave Plowman (News)]

See my thread 'A masonry question'.

Also, joists in London houses run front to back rather than the shorter route side to side - often found elsewhere.

I've never seen terraced houses with a common roof void in London - but they're common enough elsewhere.

[Tony Bryer]

I came across a few on older houses in the Kingston area built before the first building byelaws (c.1875). Inner London, as previously noted, had byelaws back to the days of the Great Fire

I came unstuck once on a loft conversion I drew the plans for in Tooting, built as a council house c.1908 so it probably didn't go through normal building byelaw procedures. Not only was there no party wall in the loft on the non chimney side - which of course I spotted (there was a plasterboard and stud wall in the loft) - but the party wall was half-brick (4 1/2"). Solved by putting a channel along the entire length of the wall to disperse the loads from the cross steels.

[Andy Dingley]

They're generally forbidden by byelaws in any sort of industrial revolution-timescale city, where they were building cheap terraces at this time and they recognised the fire issue. First ones I ever saw were in Cambridge.

In Bristol they supposedly had such strict rules for this that many houses of the mid-19th century take the partition wall up through the roof and have it visible outside. As you can imagine, this requires a vast amount of flashing that can fail in the future. That excellent book "The Construction of Houses" (?) written by a couple of UWE (Bristol) lecturers has a little rant on the subject, also one on Bristol's earlier fondness for the butterfly roof and its infamously leak-prone central valley.

[Tim Streater]

Are all such valleys leak-prone? Alternatively, what should one be doing with same on a regular maintenance basis?

[Mathew Newton]

Good book that. Just a shame I can't persuade the other half that it is eligible as an always-out 'coffee table' book...

(I can understanding the Screwfix catalogue veto)

Mathew

[Owain]

His 'n' hers coffee tables?

Yeah, keep that one for those awkward moments in the bedroom when you need to price up the OH's latest bright ideas before lights out.

Owain

[Tony Bryer]

On the plus side, it does mean that each owner can re-roof without affecting their neighbours.

The ultimate in daftness can be seen at

the middle of the pic you might think you're looking at two terrace houses. They were built 1995 in the style of the area - save that the area is stock brick, not red brick, but let's not be picky. Except they're not terrace houses, rather two flats one above the other, and the 'party wall' is just there for show - it sits on a steel beam at loft level IIRC. LBRuT planners at their best!

[Dave Plowman (News)]

Ah. So post 1875 would mean no common roof space? If so, that explains it. The big expansion took place somewhat after this. Just about every Victorian house seems to be 1880 onwards.

[Dave Plowman (News)]

Indeed. I've been very lucky with my neighbours, but could imagine the grief with an awkward one. I'd have been awkward too if my neighbour had wanted to re-roof with concrete tiles (as some did before the council clamped down on it) and there were no party wall to separate the roofs.

Absolutely brilliant. ;-)

[Andy Dingley]

It's 150 years old. It might not be you it chooses to leak upon, but someone is going to get it.

On the plus side, they make themselves obvious pretty quickly.

Move.

[Tony Bryer]

I'm a bit rusty on this stuff now, but the Public Health Act 1875 gave local authorities the power to make building byelaws if they wanted to: TPTB produced Model Byelaws that LAs could just adopt if they wanted or they could modify them as required. Then in 1965 E&W wide building regulations replaced byelaws save in inner London which was subject to completely different legislation.

You see this on my old patch of RB Kingston. In what was Malden & Coombe the byelaws would only allow four houses to be connected to a common drain, then out to the sewer in the road. There is one exception I know of where in return for a bit of land for road widening the Borough Engineer agreed to eight - so much for hydraulic principles. In next door Surbiton there are estates with no soil sewer in the road, just a 300mm pipe running behind the houses - can be problematic if extending.

[Andrew May]

Would that be this one?

[jgharston]

Dipstick next door to me did that:

roof was so heavy it was pulling the spars out of my roof, causing my valley at the back to come apart. He then complained about *me* causing the rain to leak in *his* flat.

First thing the new owner did a few years ago was completely strip the roof and replace it with artificial slate.

JGH

[docholliday]

I think that the main problems are that first, they're more difficult to get to for repairs, clearing of leaves and so on, and so they don't get maintained as frequently as eaves gutters, and secondly, because they run over the central area of the house, any leaks are likely to cause immediate problems, whereas eaves gutters may overflow and send water down the walls where it may be noticed before problems get too serious. I remember looking at one relatively large building where the roof had iner slopes running down to a flat roofed area in the middle - the water from this was taken through the attic in an open channel which would overflow if the gutters got blocked with leaves!

[Tim Streater]

Blimey.

I think due to extensions done before we bought there's two valleys - I had the roof cleared of moss earlier this year but will keep an annual eye on it.