20 Aug 2005

Whither the housing market?

Anybody want to buy a house in Norfolk? From my own humble experience, it would seem the answer is NO. I have been trying to sell this fine-looking former pub complete with a detached studio, in the village of East Bilney, for 12 months now and despite several price cuts and masses of viewings, and no less than four “Sale Agreeds,” it remains unsold. In fact it starts life with a new agent, Belton Duffy, from the start of this coming week.

The most recent sale agreed has fallen through because our buyer has lost his buyer. Again. This particular buyer is now responsible for two of the four failed sales and he may yet make it across the finishing line to become the proud owner of Swanhaven. But he is moving from a smaller house which is (or should be) attractive to first-time buyers and, as everybody keeps telling us, first-time buyers are thin on the ground at the moment.

Ten days ago, our now ex-agent rang to say he was “very confident” that our buyer had landed a good first-time buyer and that our deal was back on again. He added that he just had to run through some credit checks on the first-time buyer, what he referred to as a “qualification procedure.” He was awaiting an accountant’s report and the accountant was away on holiday. So far, so Norfolk. This week, the accountant’s report turns up, the young man comes in for his qualification meeting, he passes with flying colours, the deal is on, the chain is live. Closing the deal is the very stuff that estate agents live for and I can’t help but get caught up with his enthusiasm, especially as this deal has taken so long and proved to be so problematic.

Time to pop open the champagne? Not quite. The next morning, the young man has “reconsidered.” He is just off on two weeks holiday and he wants to “think about it.” Yeah, whatever.

Exasperated? You bet. Angry? Not really. Stoical is the word for how I feel about it all now.

This morning as I lay in bed I started thinking about this young man, our abortive first-time buyer, and I put myself in his shoes. As a first-time buyer, he would be having to borrow maybe 95% of the £115k asking price. Whilst he would probably be delighted to know that he qualified and that his credit ratings all stacked up, I can quite understand anyone who might just feel a little reticent about getting into so much debt. Taking on a mortgage for a first-time is a defining point in many people’s lives, not quite up there with becoming a parent or getting married, but not far short either. Now in a booming house market, the attractions of a 95% mortgage are obvious: because of the gearing effect, your equity increases no less than twenty times faster than the house price. You only need house prices to increase by 5% per annum, and your equity doubles in Year One. But in a stagnant house market, there is little, if any, advantage in taking out a large mortgage, as opposed to renting. And, of course, in a falling market, which Norfolk has been for the past 12 months, anyone with a large mortgage is losing twice over. So yes, I can understand this guy’s reticence to become a player in the Norfolk housing market.

No doubt our little drama is being replicated tens of thousands of times across the country. It’s hard not to extrapolate, to read this young man’s behaviour as a proxy for the whole housing market, at least as far as first-time buyers are concerned. The agents will be trying to figure out where the price point is which switches his behaviour from sniffing around to actually closing the deal. But from his point of view, a mortgage is a mortgage and whether it’s £105k or £95k or even £60k, it’s still a huge amount of money and it’s really only an attractive option for him if taking on this mortgage brings wealth along with it, and the only mechanism that delivers that is rising house prices. Viewed from this perspective, it’s easy to grasp just why the housing market tends to overshoot on the way up and on the way down as well. It’s why the economists fabled “soft landings” so very rarely happen. It doesn’t bode well for the next couple of years, does it?

So go and enjoy your holiday, unknown first-time non-buyer. I have a sneaking admiration for you and I suspect you may well have made the right decision.

Meanwhile, anybody want to buy a house in Norfolk?

19 Aug 2005

What’s Belgium got to teach us about housebuilding?

To British students of modern manufacturing methods, Danilith are known (if they are known at all) as the Belgian housebuilders with the robot bricklayers. But that is only a small part of the story. For Danilith is a vertically integrated housebuilder of the type that just doesn’t exist in the UK. They are a family business that has been running since the 1920s and they own a large plant in Wortegem, which they use to build as much of their houses as they possibly can. Not only do they prefabricate wall, floor and roof panels, but they make their own joinery as well. They employ 260 people, use very few subcontractors and they undertake around 250 projects a year, mostly individual homes in Belgium and Holland, mostly fully finished.

Let’s just consider this last sentence. 250 houses built each year by 260 people. That, in itself, is remarkable. No one at Danilith works more than an 1800hour year if they can help it — Belgian overtime is very heavily taxed so there is an incentive to stick to the contracted hours. Of these 260 employees, just 30 work in the factory, another 100 on site erecting and finishing the houses and the remainder in various admin roles. So essentially, 130 workers are building over 200 houses each year. That’s just under 1200 hours labour going into each house. In comparison, the standard British site-built home takes 3000 hours to construct. Danilith workers are thus over twice as productive as their UK equivalents.

This is reflected in the prices charged for Danilith’s homes. Their brochure shows that the selling price is almost always under €1,000 per sq m (£690/m2). But in Belgium, new homes attract VAT at 21%, which is included in this figure. It also includes 4% taken for design fees and a mandatory 1% fee payable to a private security firm to oversee the construction sites. The net sales price is in fact just €800 per sq m (£550/m2). It’s difficult to see something of equivalent quality in the UK costing less than £900 per sq m. In fact most MMC advocates say that you can’t build at less than £1,000 per sq m unless you are constructing identikit houses in long production runs. But Danilith’s homes are all different, although the elements used to put them together are modular.

In so doing, Danilith produce a very high quality house. We are used to seeing timber and steel framed houses built in factories but Danilith work mostly with brick and concrete, reflecting the prevailing preferences in the Benelux countries and France. The 10metre-long wall panels passing through the Danilith plant are not unique: in Germany, basements are commonly constructed with prefabricated walls. But Danilith have added to this a robotic brick laying machine which first slices the bricks in two lengthwise and then lays them face down on a flat bed, against some retardant paper. Mortar is subsequently brushed into the joints from above before three more layers, concrete, polyisocyanurate insulation board and lightweight concrete are added to the beds, the whole process taking around four days to cure and the final wall thickness being around 250mm. Finally, the walls are hoisted vertically, to be finished by hand on the last of the production lines. Windows, doors, electrical channels and plumbing runs are all set into the walls as they are being constructed. You can view the 15 stage process on the website www.milbank-danilith.co.uk. Floor panels are constructed elsewhere in the plant. Roughly a house a day passes through the plant: on a traditional British building site this would represent the efforts of around 600 hours work. In the Danilith factory, it’s 25 workers on an 8-hour shift: 200 hours. Plus, of course, a lot of investment in machinery and forty years worth of know-how.

The technology used by Danilith is far from hi-tech. It’s the sort of thing that is used on production lines across the globe. Parts of the process are still carried out by hand and compared to the latest robot car builders it all looks a little primitive. And there are many other smallish housebuilding businesses in Germany and Scandinavia using similar finished-panel systems. However, in the UK, the nearest we come to factory production in housing are the numerous timber frame companies who semi-fabricate wall and floor panels, sometimes referred to as open panel building. This requires insulation, services and finishing on site, both internally and externally.

Danilith see themselves as custom homebuilders first and foremost. Although they make windows and staircases, as well as the wall panels, they don’t sell them to third parties; they only supply their own projects. However, they do undertake a little spec. building from time to time but usually to fill gaps in the production schedule that would otherwise have them laying off staff. This is quite revealing in itself. It’s frankly hard to imagine a British firm adopting such an attitude. Indeed, it’s just the sort of action that shows the gulf between Anglo-Saxon and Continental business practice. Whilst we are busy cutting costs and growing market share, the Belgians are putting the interests of their workforce first and foremost. Whilst many British economists would highlight Danilith’s working practices as being a prime example of Eurozone featherbedding, they would also have to admit that it’s resulted in productivity levels which we in the UK can only aspire to some time in the not-so-near future. The Belgians are clearly doing something right.

This remarkable company would like to transfer some of its know-how to Britain. They have found a willing partner in Milbank, who, like Danilith, area a family-run company with a keen interest in masonry prefabrication. Milbank are big in precast flooring in South East England and have slowly grown their business to embrace haulage and joinery. But they are not housebuilders. Both Milbank and Danilith are keen to start building homes in the UK but there are significant obstacles to overcome in order to establish a British version of Danilith.

Perhaps the biggest problem is that there simply is no tradition of custom home building in the UK. On most of the continent, custom home building is the principal route by which detached houses are built. Individuals buy plots — relatively cheaply — and commission a new house to be built on them, without spending a great deal of time working on the project themselves. In Britain, the new homes market is dominated by speculative builders who build solely for sale: there are around 15,000 individual homes built each year but most of these are taken on on a semi-DIY basis with the selfbuilders acting as their own contractors. The burgeoning timber frame sector prefers to offer a water-tight shell option and lets the selfbuilders finish the houses off in their own time. One or two Continental companies offer a full-build service, notably Huf Haus and the Swedish House Company, but they only account for a tiny number of new homes each year, probably under 100 in total.

Typical of Continental custom homebuilders, Danilith is set up to build one-offs. Everything in the Danilith system is modular but provided the design fits the modules, almost any design can be built. They don’t aim to achieve economies of scale by mass production: their goal is to simplify everything down to a set number of options and to avoid prototyping. That way they avoid mistakes and they keep costs to a minimum, without becoming too repetitive.

Quite why the major British housebuilders have failed to take up factory-building Danilith-style is a mystery. Their pattern book approach to housebuilding, combined with the guaranteed volumes, ought to lend itself to prefabrication. But for some reason vertical integration has never appealed to British builders and no one has ever seen fit to try. The only plc housebuilder to currently use a significant input of prefabrication is Westbury, who have built the largest timber frame plant in Europe (Space 4) to supply some of their new homes. But Space 4 is a long way short of what the likes of Danilith and Huf Haus do.

The big question is this. Can the cost savings shown by Danilith be achieved simply by copying the technology or is the different business culture an essential part of the mix? Whilst it ought to be easy to introduce robot bricklayers, it will be much harder to integrate the Continental work ethic needed to keep the robots ticking over.

15 Aug 2005

Cleve Prior Webcam

Many selfbuilders have run websites, photographing and recording their builds along the way. But this is the first one I have come across where a webcam has been installed so you can watch the action "live." The house is in Lancs and is being built by Tim and Val Fairless, frequent contributors to the selfbuild list. The webcam isn't quite as gripping as the cricket, but it's tempting to leave it on it the corner of your screen. As the caption says "If the image does not move, then nothing is happening."


Basement Advice

I need lots of information on building a basement. I'll take anything from construction, design, good build, bad builds, tanking, damp proofing, companys, as I said, anything. My project is to build an art studio with a basement measuring 30 feet long by 20 feet wide, going down 6 feet to subfloor leaving two feet about ground level for windows and vents.

Thanks Mostyn Powell

Mark reckons:

The one thing that people really fear, when considering basements, is that they will leak. And it's not a groundless fear. The insurance claims records on new basements is appalling, enough for insurance bodies like the NHBC and Zurich to often specifically exclude basements from their cover. The problem is that relatively minor errors can result in total failure whereas above ground they would most likely pass unnoticed. And of course leaky basements are difficult and costly to fix.

There are basically two techniques for stopping basements leaking: tanking and drainage. Ideally both should be employed. There are several ways of building basements and they are all potentially excellent yet none of them is completely foolproof. You need an appropriate design to start with and you need to employ contractors with above average competence.

One of the problems with basement design is that no one quite knows who to talk to at the outset. If you go to a "basement specialist" they will most likely be trying to sell you their pet system, regardless of whether it is suitable for your site. An architect? Probably won't have a clue. Neither will most structural engineers. An "experienced groundworker?" You may be lucky, you may not, not many UK groundworkers have ever built a basement. You could do worse than check into the Basement Information Centre www.basement.org.uk and key into their database, although it keeps throwing up Phil Hewitt as the only independent consultant philhewitt@btconnect.com

One other tip,
Selfbuilder Lol Berman is just completing a new house in Cambs with a 17x8m basement. He costed out four options at the outset:
• ThermoneX £77k (ThermoneX make prefab basement walls, craned into position)
• Beco £56k (Beco are an ICF business, using polystyrene moulds into which concrete is poured)
• Ordinary Local Groundworkers £58k
• David Ball's Pudlo System £41k (Pudlo is a waterproofed poured-in-situ concrete system produced by the David Ball Group www.davidballgroup.com)

He went with the Pudlo system and thus far it's been fine.

12 Aug 2005


David Birkbeck’s use of the Finnish building board Sasmox as a wall/ceiling board is unusual. The UK selfbuild community are keen users of Fermacell, a similar product, made in Germany, and I was interested to make the comparison between the two boards. Sasmox is slightly more expensive than Fermacell: a plasterboard:Fermacell:Sasmox cost ratio would go 1:3:3.5 or maybe that should be 2:6:7. It’s a very simple product made of spruce cuttings (of which Finland has no shortage), waste gypsum and water: it’s pressed together in stainless steel clamps, there are no glues or additives. Whereas Fermacell doesn’t really like water — it tends to belly — Sasmox is virtually unaffected by it. Where Sasmox really wins out over Fermacell is with the finish: it’s smooth and shiny, doesn’t really require any painting other than filling between boards and over screw holes.

The downside of all these heavy boards (Sasmox weighs 1250kg/m3, about 40% more than plasterboard) is that they are really not easy to work with. You need a jigsaw to cut them rather than just scoring with a Stanley knife, plus you really struggle to get the boards onto ceilings simply because they weigh so much.

Sasmox is distributed by the Panel Agency www.panelagency.co.uk, Tel 01474 872578. The contact is Roger Kingsley who is happy to deal with largish (whole house) orders direct.

Chateau Birkbeck nears Completion

Friday morning, drive down to Thaxted to see how David Birkbeck’s new house is coming along. David was the first editor to hire my keyboard, back in 1996, and now he runs a consultancy called Design For Homes which sets out to get housebuilders to hire architects. He is in the middle of his first selfbuild and I have been following the story ever since he first put an offer in on the plot. The house is, naturally, very designey: the architects are Snell David. I was last here in January when the extraordinary spine wall was taking shape with these unusual blocks, which are glue-mortared.

Now the house has taken shape around it and it’s a magnificent structure. It’s a magnificent site, which helps matters; a sort of woodland glade with a large pond and the house has large glazed panels looking out over the pond. If I was feeling critical – and I’m not today – I could say that it suffers from being an architect-driven project, which is overly complex and unnecessarily fussy. But on this balmy August day, it just looks very cool and comforting and, indeed, just a little inspiring. David isn't on site but he speaks to me over the phone and enthuses about the whole structure being both very modern yet very Essex. I think he's referring to the timber wall panels but even these turn out to be something unusual, in this case Thermawood, a heat treated softwood which should last decades, "unlike all that nasty cedar," he says "which is already beginning to look tatty." David can be very funny; whilst he works as a champion of good house design, this doesn't mean he champions ALL new house design.

Like most selfbuilds, this house seems to be being assembled by all kinds of odd people. I am met and tea-ed by Clare’s brother who is about to become a primary school teacher. Upstairs are two lads who normally work as exhibition display builders: they are putting Sasmox building board in place on the many studwork partitions. This is a non-traditional skill if ever: no one here has ever worked with Sasmox before. It’s heavy and a little fragile but it doesn’t need finishing, unlike plasterboard.

The scaffolding is about to be struck and David says he hopes to be in within “a few weeks.” Having knocked about the selfbuild scene for many years, I should know that this is wildly optimistic but sometimes you can’t help but be dragged along by all the optimism.

8 Aug 2005

UK Land Use Statistics

The following text is taken from a short article by James Woudhuysen, Professor of Forecasting & Innovation at de Montfort University. It appeared in the Housing Forum Newsletter. James tells me that he drew it from The Office of National Statistic. He also tells me to mention his book "Why is construction so backward ?", John Wiley & Co, 2004.

In Britain 57.5m people live in about 24m dwellings. If household growth is to match population growth, 64m people will, by 2030, need a stock of 26.7m homes. But households are getting smaller, so call that 2030 total for homes 29m – five million more homes than exist in Britain in 2005.

Then there is the rate of stock replacement. Today, ordinary flats or houses will just about last 100 years – given lots of refurbishment and DIY. So take it that, over the next 25 years, Britain will need to replace, on a 100-year cycle, stock that rises from 24m to 29m units. That means building an additional 242,000 new homes in 2006, racking up to 290,000 in 2030. Over 25 years, therefore, 6.65m new homes will be needed just to replace worn-out old ones. Add the 200,000 homes required for annual new household formation to the average of 266,000 required for annual stock replacement and one gets an annual output of 466,000 homes –11.65m over 25 years. That’s a little different from the annual average of 171,225 homes built in Britain since 1997.

Wouldn’t the millions of new homes we propose concrete over Britain’s green and pleasant land? Wouldn’t they mean, at the very least, still more urban sprawl? It’s time to lay these myths to rest.

The land cover of Great Britain is 23.5m hectares, used in 2002 as follows:
• 1. intensive agricultural land – 10.8m hectares, or 45.96 per cent
• 2. semi-natural land – 7.0m hectares, or 29.78 per cent
• 3. woodland – 2.8m hectares, or 11.91 per cent
• 4. settled land accounts for 1.8m hectares, or 7.65 per cent
• 5. water bodies – 0.3m hectares, or 1.28 per cent
• 6. sundry other categories – 0.8m hectares, or 3.42 per cent.

If settlements are added to the ‘sundry’ component (largely transport infrastructure such as roads and railways), then built-up Great Britain consists of about 2.3m hectares, or just 10 per cent of the land available. Clearly, considerable growth in both population and household numbers can be accommodated – both in high urban concentrations, and as dispersed settlements integrated into the landscape.

5 Aug 2005

Who owns what

This takeover bid for BBP set me thinking about what has become of all the businesses and brand names that once supplied the UK housebuilding industry. Here follows a far from complete list of “where they are now.” The heavy side has almost all gone overseas; the only big local player left is Hanson, which makes it an attractive target for other would-be empire builders. It’s ironic that Hanson Trust, as it then was, started a lot of this consolidation process back in the 70s and 80s, only to be hammered for it by the City when it went out of fashion in the 90s.

RMC: readymix concrete and cement. Now owned by Cemex of Mexico. Also own Russell roof tiles and Rugby Cement and Thermabate

Blue Circle: Britain’s original cement company, an original constituent of the FT30 in 1953, taken over by Lafarge (large French conglomerate) in 2001

ARC: part of Hanson, medium sized UK conglomerate, which includes Hanson brick and Thermalite and the old Marshall’s Floors business

Castle Cement: part of Heidelberg Cement, quoted in Germany

Bradstone: a brand owned by Aggregate Industries, a UK asphalt and concrete conglomerate which was itself taken over by Holcim of Switzerland in March 2005 for £1.8bn

Tarmac: now the Industrial Minerals Division of Anglo American plc, which includes Tarmac Topfloor and Durox

Ibstock Brick: taken over by CRH, large Irish conglomerate, in 1999

Celcon: Owned by H+H International A/S, a Danish company.

Baggeridge Brick: an independent brick manufacturer, quoted on the London Stock Exchange (LSE) till August 2006. Then it was taken over by the acquisitive Austrian group Wienerberger for £89m. Two years previously, Wienerberger had bought thebricksbusiness for £100m. The 2006 acquisition lifts Wienerberger to No 3 in the UK brick market at around 24%. Hanson is No 1 at 33%, CRH is No2 at 30%.

Redland: taken over by Lafarge

BPB: once British Gypsum, independent (but for how long), quoted on LSE. As well as plasters and plasterboard, it owns Artex and Rawlplug

Marley: now owned by Etex Group of Belgium

Boulton & Paul Joinery: originally bought by Rugby cement, sold to privately owned US joinery business Jeld Wen in 1999

John Carr: another independent joinery producer, also owned by first Rugby and merged with Boulton & Paul, now subsumed into Jeld Wen

Magnet Joinery: once quoted, now owned by the Swedish kitchen company, Nobia

Premdor Crosby: owned by Masonite of Canada, quoted in Toronto

Anglian Windows: based in Norwich, went public in 1992, MBO in 2001

Velux: private Danish company

Osma: always owned by Dutch group Wavin. Wavin is short for WAter and VINyl! Used to be part owned by Shell but I now jointly owned by Overijssel Water Board (who started it in the 1950s) and CVC Capital Partners, private equity.

Terrain: sold by Caradon to Geberit. Swiss plumbing supplies company, in 1999

Hepworth: bought out by Vaillant, sold on to Wavin

Baxi Potterton: now part of a plc owned by private equity, includes Heatrae Sadia, makers of Megaflo
Aqualisa: part of Baxi group

Myson Radiators: owned by Rettig, a privately owned Finnish company

Marshalls: independent, quoted on LSE.

Pilkington: independent glass manufacture, quoted on LSE

Ideal Stelrad: based in Hull, once part of Caradon, sold to HSBC private equity in 2002

MK Electric: part of Caradon group, which seems to have disappeared

Celotex: private UK company, MBO from larger American business using the same name

Kingspan: Irish public company

Jablite: brand name of Vencil Resil, taken over by Synbra Group BV from Holland

Rockwool: Danish public company

Sadolin and Sikkens: part of European conglomerate Akzo Nobel which includes what was left of Courtaulds and Crown Berger paints

Dulux: still part of ICI, as are Cuprinol and Hammerite

4 Aug 2005

BPB v St Gobain

Yesterday, the French building materials conglomerate, St Gobain, put in a hostile bid for BPB, our principal plaster and plasterboard manufacturer. After two friendly offers were rejected, they have now gone hostile at 720p a share. But the institutions want 750p, maybe even 800p and won’t accept the St Gobain offer as it stands. Before all this takeover kafuffle started, BPB shares were trading at around £5 and had, in truth, been a very unremarkable investment over the years. BPB turns over just over £2 billion a year which, coincidentally, was roughly its market capitalisation before St Gobain appeared over the horizon. It’s expected to make a profit of around £250 million this past year, that’s 36p per share, and it pays roughly half of this out as dividend. At £5, BPB was priced at around 14 times annual earnings, roughly in line with the sector: at £8, this ratio goes up to 22 times which, as far as the City is concerned, is off the top of the scale.

So why do the French seem so keen on buying yet another piece of the UK building supplies industry? Would you pay £300,000 for a house which was reckoned to be worth £200,000 just a few weeks ago? It appears that St Gobain are prepared to. What is it that attracts St Gobain so much?

BPB is not just “another house.” For one thing, it retains the exclusive rights to mine gypsum in the UK and whilst mined gypsum is not exactly a priceless commodity, it’s been incredibly helpful to BPB over the years in keeping rivals at bay. Most mined British gypsum is pink: the pink colour is actually an impurity but it’s become so accepted that when the other two European manufacturers, the German privately-owned Knauf and the French conglomerate Lafarge, wish to sell gypsum plasters into the UK, not only do they have to ship the stuff across the Channel but they have to die it pink as well, otherwise British plasterers won’t accept it.

In fact BPB used to be known as British Gypsum. It began life in 1917 and it was only in the 1990s that it changed its name to BPB (British PlasterBoard) to reflect the fact that boards were now the main part of the business, plus the fact that it was by then an international trading company and far from exclusively British. Plasterboard was originally invented in America in 1916 by the US Gypsum Company: they called it Sheetrock and they tried for years to get builders interested in their innovation but to little avail.

It was the need to reduce construction manpower in World War 2 which eventually caused Sheetrock to take off. It did away with the need for wood lath, multiple plaster coats, and days and days of drying time — hence its American generic name, drywall. In Britain, we have always referred to it as plasterboard. Installation was simple: the sheets were nailed up, the nail holes were filled, paper tape was used to cover the joints, and a textured coating was trowelled on to help disguise the defects. Voila, as the directors of St Gobain might say.

In Britain, the take-up of these boards was similarly slow. British Gypsum plugged away throughout the 50s and 60s trying to get builders to accept this modern method of construction but, because the bulk of our housing is masonry, most builders still preferred to use wet plaster. It didn’t matter a great deal as the company had a monopoly on all gypsum products, whether bagged plasters or boards.

But the monopoly was to go in the 1980s as both Knauf and Lafarge entered the UK market. Whereas initially, British Gypsum sold plasterboard to builders as time-saving innovation (really an excuse to charge more money), plasterboard then became one of the ultimate commodity products. Its price has remained largely unchanged for twenty years. But the manufacturers countered this by making plasterboard with less gypsum and more air, thus reducing their costs. Whilst this kept British Gypsum’s bottom line ticking over, it did very little for the acoustic properties of British housing. BPB, as it now is, used this as a marketing ploy and, when the sound regs were beefed up in 2003, they “introduced” a new board called TenBoard, specifically to meet the new requirements. Why the name? The "ten" refers to the weights of the board per square metre — i.e. 10kg. Ironically, back it in the 60s and 70s, all plasterboard weighed this much!

Ninety years after its invention, the market for plasterboards is still growing and looks set to continue to grow. Although I am not a great fan of our government’s push to get everyone and their aunt to embrace Modern Methods of Construction, the truth is that they are pushing against an open door and housebuilding is going that way, whether we like it or not. One of the key difference between modern methods and old-fashioned ones is the presence or absence of water during the building process — modern methods are almost always dry methods — and plasterboard, in its many forms, is always going to form a part of any MMC construction system.

That, I guess, is St Gobain’s reasoning. Whilst the City looks at valuation in comparison with similar businesses, St Gobain are empire building and are all about fitting bits of the jigsaw into place. To them, this house may well be worth £300,000 because owing it unlocks value elsewhere. Whether it succeeds in making a sensible business is another story but at heart we have another classic encounter between the Anglo-Saxon model — everything’s for sale, at the right price —and state capitalism as practiced by the French. Whilst the French seem slowly to be hoovering up our utilities and our manufacturing base, we Brits are spending the proceeds on French property.

3 Aug 2005

Will Anderson's Folly

Diary of an Eco-Builder?

I must admit that I now cringe when I hear someone describe themselves as an “Eco-Builder.” It’s just a tad too smug for the likes of me; a set-apart term that suggests that they are somehow a cut above common or garden builders. If you have to set yourself apart from the hoi polloi, then I prefer the term “Gentleman Builder” because it’s generally a lot more to do with class than it is to do with green politics. If you really want to be green, then don’t build: there is no such thing as an “Eco-Builder.”

The Independent doesn’t share my scruples. They are currently running a weekly column (Wednesday, Property) called Diary of an Eco Builder, penned by Will Anderson who is building a large new timber-framed house in South London and is writing about his experiences. Today’s column (3 August) is interesting because it deals with one of my pet subjects, moisture management. It’s a much misunderstood subject and Anderson perpetuates many of the misunderstandings.

Myth No 1: “Our walls must obviously be robust enough to stop water getting in” writes Will, “but this is a simple task compared with dealing with moisture going the other way.” Anderson might think keeping rainwater out of the house is a simple matter but despite thousands of years trying, we still haven’t mastered it. The huge bulk of problems we experience with both roofs and walls stem not from anything weird happening with water vapour, but from rainwater ingress.

Myth No 2: “The principal movement of moisture within walls is from the warm, humid interior to the cooler, drier exterior.” What he is referring to here is the phenomenon of vapour diffusion, which occurs at molecular level. Water vapour will tend to travel, albeit very slowly, from areas of high vapour pressure (i.e. indoors) to low ones (i.e. outdoors). That’s the perceived wisdom on walls, and has been since the 1940s. Unfortunately, more recent research has shown it to be largely irrelevant. There are far more important drivers governing the behaviour of moisture in walls, floors and roofs.

Myth No 3: “We generate huge amounts of water vapour in our homes, cooking, bathing, washing and breathing.” My quibble is with the use of the word “huge” in this context. A person living in a house produces about 1 tonne of water vapour a year: on its own that sounds like an enormous, or even a “huge” amount, but set it in context. A detached house weighs around 100 tonnes and as much as 10% of this is made up of water, bound in with the building materials. This water:solids ratio is not a steady state relationship; it’s in a constant state of flux, depending on conditions both indoors and outside. Odd litres here and there produced by the occupants – a tonne a year approximates to around 3 litres a day — hardly makes any difference to the overall behaviour of moisture within the house.

Myth No 4: “Condensation occurs whenever air cannot hold any more water.” I am indebted to William Rose’s excellent new book, Water in Buildings — an Architect’s Guide to Moisture and Mold* — for nailing this one. Condensation occurs when there is a suitably shiny, non-porous surface and the temperature is below somewhere around 12°C, but it doesn’t follow that condensation always forms whenever the air isn’t warm enough to hold the water vapour. The excess moisture is frequently taken up by the materials in the room without classic condensation taking place: carpet is very good at it, so is painted plasterboard and unsealed timber.

Myth No 5: Condensation is a “greater problem if it occurs in areas you can’t see, such as inside your walls or roof, where it can do everything from undermining your building fabric to rotting your building fabric.” It sounds absolutely terrifying, and it’s true to say that water can and does damage building fabrics. But to blame it solely, or even mainly, on our indoor activities is just plain wrong, although, to be fair to Anderson, this analysis is at the heart of BS5250, the standard which sets out the parameters for the Condensation Risk Analysis which underpins much of our design of timber frame housing and roof building. The Americans refer to it as the profile method and, according to Rose, using it inappropriately has led to “wildly exaggerated over-predictions of the likelihood of diffusion-related moisture problems.” Rose continues “A very informal survey among building science colleagues seems to indicate that diffusion-related moisture problems account for less than 1% of the moisture problems found in buildings. We have been seriously sidetracked by the profile method for the past 50 years.”

Does it matter that the likes of Anderson are regurgitating nonsense? Arguably, it’s harmless nonsense. We have lived with this largely incorrect analysis for 50 years and it hasn’t caused us much harm if only because of another, far more useful, practice we also have, which is maintaining a vented cavity behind the rainscreen or brick wall on timber framed houses. But there are many businesses out there making a good living playing on people’s fears of the “hidden menace of unseen condensation.”

Anderson finishes his article by running through his spec for his walls: he appears to be installing a heavy duty vapour barrier (the key weapon in the fight against condensation, according to the profile method) and a “breathing wall” routine as well, using Warmcel, the recycled newspaper insulation which sells itself as a natural alternative to plastic vapour barriers. I have never heard of anyone doing this before: it’s either plastic vapour barrier or breathing wall, not both combined. I would have serious reservations about Will Anderson’s design: the whole point about breathing walls is that they are designed to dry both outwards and inwards: placing a plastic vapour barrier inside his Warmcel may stop this happening. Heavens, it may even lead to the very thing he is trying so hard to prevent. Might our Eco-Builder be in the process of constructing one very soggy house?

*Water in Buildings — an Architect’s Guide to Moisture and Mold. Author William B Rose. Published by John Wiley and Son 2005. £31.15