Today, I’m going to talk about alternative methods of construction, of which there are probably more around now than ever before. I’ll give some reasons for that in a minute.
First, though, it’s worth asking why we should consider alternative methods of building in the first place?
Well, the great majority of selfbuilders aren’t hugely experienced at major projects. My wife and I certainly weren’t with our self build. We’d previously renovated a couple of houses – mainly on a DIY basis – but we didn’t feel knowledgeable or confident enough to tackle a completely new build.
So we did what most self builders do which is to find an architect and a contractor to do the bulk of the work for us.
Now professionals are obviously essential for something as complicated as building a house. But, like the rest of us, they will have a preferred way of doing things, a method they have most experience of and find most convenient. And it may well be exactly what you need. But it might not be.
Given the nature of building, it can be years before you find that out, usually when you come to carry out a major repair or renovation. Or when you find your fuel bills becoming prohibitively expensive.
So, even if you’re convinced you know exactly what form of construction you want, it’s always worth spending a little time looking at the alternatives. They may, for example, solve a problem you haven’t considered, or which your architect or builder may have solved in an unnecessarily complicated or expensive way.
At worst, you’ll waste a few hours. At best, you may find it makes a dramatic difference to your project, and its costs, both short-term and long-term.
But first let’s look at what we mean by conventional or traditional building. To today’s house building industry it means brick and block.
On the continent they say the British build houses twice. First we put up an inner wall of concrete blocks. This does all the hard work of holding up the floors and the roof and providing the main structural support.
Then we cover this up with an outer wall of brick which provides protection from the weather. But it’s mainly designed to look good and give the house its distinctive character.
Between the walls a cavity is left, typically about 100 millimetres – or four inches – wide. Originally it was intended to allow any moisture seeping through the brickwork to drain away, leaving the inner wall dry. Nowadays, depending on local weather conditions, it’s either filled or part-filled with insulation, designed to keep the house warm and reduce fuel bills.
Bar the cavity and the insulation, this is pretty much how we’ve been building houses for centuries. We deliver basic materials to the site and assemble them largely by hand.
Everyone in the building industry is familiar with the process. The materials are available everywhere. And, broadly speaking, it’s still the cheapest way of building, at least in terms of material costs.
So why should we consider anything else?
Well, three main reasons. The first, and most important, is energy efficiency.
Fuel prices, with a few hiccups, have been rising steadily since the 1970s and show no sign of slowing down. The government has responded to that by upgrading the Building Regulations which now require new houses to be better insulated and more airtight than ever before.
That’s certainly the most efficient way of reducing the amount of gas and electricity we use. But traditional building, as we know it, was never intended to accommodate such large amounts of insulation or be so draught-free.
At this point I always tell a story of going round a thirties property a few years ago with a surveyor who was delighted to find fierce draughts roaring through the empty cavity and under the suspended ground floor.
As far as he was concerned the house was in superb condition because it was so well ventilated. Damp or rot would never be a problem and the 70-year-old floor joists we exposed looked brand new. This was great for the house, but not so good for anyone living in it. In wintertime it was absolutely freezing and heating cost a fortune.
Building a house in the same way today but to modern standards can create real problems. For example, if you use the cheapest insulation – fibre glass or mineral wool – the cavity has to be at least 150 millimetres – or 6 inches – wide.
Add the depth of the brickwork, blockwork and internal plaster and the total depth comes to around 380 millimetres – around 15 inches. Even then, your local building control department might require additional insulation on the internal side of the wall.
Meanwhile, the cheapest way to insulate the roof involves laying around a foot of mineral wool on the loft floor, making it completely unusable as accommodation or storage space.
If you want to build an ultra-energy efficient house, the walls need to be even wider. The Denby Dale house, which was built about six years ago in Yorkshire, was the first traditionally built house in Britain to achieve the passivhaus standard.
This is the best known method of building very low energy houses where the annual heating bill can be as low as £80. But it was developed in Germany where most houses are either timber frame or built with solid walls without a cavity.
The Denby Dale house ended up with a cavity around 12 inches wide, packed with fibre glass. The total width of its walls, which had to be local stone on the outside, was over 500 millimetres, getting on for a couple of feet.
If you have a small plot, or the space for your extension is restricted, walls approaching that width will really squeeze the internal space. And you’ll be wasting a significant amount of the cash you’ve paid for the land.
There are ways round it, of course. You can use more efficient forms of insulation, typically rigid foam polyurethane produced by companies like Kingspan and Celotex. This is around twice as thermally efficient as mineral wool but around three times the price.
Another common solution is to build the inner walls with aircrete, which is a kind of Aero chocolate bar version of standard concrete blocks.
Aircrete blocks are full of tiny air bubbles, which makes them much more thermally efficient. But they are more expensive than standard blocks and likely to become even more so because there’s been a recent shortage of one of their constituent materials.
Achieving high standards of airtightness in a brick and block house depends on careful detailing and high levels of monitoring. Both of these can be hard to achieve when jobs are based on fixed prices and tight schedules.
The point is that sticking with traditional methods is a lot more complicated than it used to be and it’s harder to get right. But the good news is that many of the alternative methods now available were developed to deal with today’s energy efficiency standards and they could make your build much easier.
The second reason to look at alternatives is the question of labour costs. Since the 2008 recession it’s estimated that over 140,000 workers have left the building industry. Traditional building depends on skilled tradespeople, particularly bricklayers, carpenters, joiners and plumbers.
But around a quarter in the UK are now over 50 and there hasn’t been enough investment in their replacements. Instead the industry has relied on recruitment from abroad, but with Brexit looming no one really knows how long that can continue.
As a result it’s getting harder to find skilled craftsmen and, when you do find them, they are getting more expensive.
Many alternative methods of building are specifically designed to need fewer on-site skills. Some are effectively do-it-yourself, at least in part, and these are particularly useful to selfbuilders on a limited budget.
Reason number three for considering alternatives is speed – not just a faster speed of building, which will save on your labour costs, but the speed at which your new house becomes properly habitable.
Traditional brick and block houses are literally hand built – each block and brick laid individually. It can take up to six months to complete a build and, until the roof goes on, everything takes place in the open air.
If it gets too cold to pour concrete or lay mortar, work stops. If the weather’s wet, the block and brickwork, as well as exposed timbers, can become saturated. As a result, it can take a new house up to a year to dry out fully.
So what are the alternatives?
The most well established is timber frame. It accounts for about 20 per cent of the UK house building market as a whole, and 70 per cent in Scotland.
In a timber frame, it’s timber studwork not concrete blocks that holds everything up. Even though the studs are comparatively slim, they are braced by sheets of plywood or OSB which gives them more than enough strength to support a house.
Timber frame is popular because it eliminates many of the drawbacks of brick and block.
For a start, timber is inherently more thermally efficient than masonry. Not only that, because the frame is hollow, insulation can be fitted inside. It doesn’t have to be squeezed into the cavity. So the total depth of the wall can be kept down.
Timber frame is also easier to make airtight than brick and block. To prevent moisture produced inside the house from reaching the timber and causing it to rot, a vapour barrier – usually taped sheets of polythene – is attached to the inside of the frame before it’s drylined with plasterboard.
Even more importantly, time on site is reduced because most timber frames are built in a factory under controlled conditions. This allows the dimensions to be much more precise than with a traditional build and gives much greater control over costs and build quality. There’s much less chance of a subcontractor covering up a mistake because he’s in a hurry to get to his next job.
The main structure is delivered to the site on the back of a lorry and it’s erected within a few days. As soon as the roof is on, the internal trades can start work while the outside shell is being built.
If it’s properly organised, the whole build process can be completed within 12 to 14 weeks, much quicker than brick and block. Even better, it’s a largely dry process. All the internal walls are plasterboarded, ready for immediate decoration, so there’s no lengthy drying out period after completion.
Like all systems, however, timber frame isn’t perfect. Because the frame is a single, precision-made shell, last minute changes are very difficult to make.
And if you’re going to hang heavy objects, like kitchen wall units or wide-screen TVs on the plasterboard walls, the studwork will need to be braced internally to provide the extra support. So you need to think about that before the plasterboard goes up.
But many of the most recent developments in timber frame are ironing out these problems. Instead of completing the frame on site, more and more is being prefabricated, largely to meet the demands of ever rising energy efficiency standards.
In so-called ‘closed panel’ systems all the insulation, vapour barriers, external waterproofing and even plasterboard is put together in storey-high panels in the factory. Then these are simply slotted together on site.
Some systems do this with entire walls, with doors, windows, wiring and plumbing all factory-fitted, saving even more time on site. This is much more common in Scandinavia and Germany with companies like Hanse Haus and Baufritz, who now operate over here, but it’s starting to be used in the UK, and it makes an enormous difference to overall build quality.
But perhaps the most promising technical development, at least for the moment, is the structural insulated panel, or SIP.
SIPs simplify the construction process even further by combining the insulation and the structure. A SIP panel consists of a layer of rigid foam insulation – usually polyurethane or expanded polystyrene – glued between two sheets of oriented strand board.
Unlikely as it sounds, this makes it enormously strong – in fact, up to six times as strong as a standard timber frame.
Building a SIP house involves simply gluing and nailing one ceiling-high panel to another until a complete storey is made. The panels form a completely self-supporting shell so the entire space inside can be open plan, if you choose.
SIPs can also make roof panels which don’t need internal support. They simply lean together to make the roof shape, leaving the attic space clear. This makes them ideal for rooms in the roof.
But it’s as insulation where SIPs really score. Because the insulation inside each panel is pressed against the next a continuous airtight barrier is created. This makes a really big difference in avoiding heat loss. A recent German study showed that a gap as small as one millimetre between sheets of insulation can make them up to 40 per cent less efficient.
So, if you really to need to have the slimmest possible walls for your project, SIPs are hard to beat. They’re also a good choice if you’re planning to build an ultra-energy efficient house.
There’s one other type of timber frame which should also be included, even though it’s actually much more traditional than brick and block. That’s oak frame, built in the way oak framed buildings were constructed from the middle ages to Tudor times with exposed beams, high vaulted roofs and mortice and tenon joints fixed with hand-crafted wooden pegs.
Most systems use green oak, which has been felled in the last 18 months, so that, like brick and block, it will need to dry out after completion. This also means the oak will shrink, providing all the cracks and splits which give this wood its distinctive character.
That creates problems for external elements like windows and doors which don’t shrink, so a degree of remedial work may be needed. But to meet current Building Regulations most oak frames are now enclosed within an insulated shell covered with brick or timber cladding, so the oak frame is only exposed on the inside. It still looks marvellous, but it’s an expensive option.
Now if you really want to save money there are systems which are virtually do-it-yourself – at least, in part – and you won’t need to re-train as a carpenter or bricklayer.
Probably the best known is Insulated Concrete Formwork or ICF. Concrete is more commonly used for blocks of flats or commercial buildings where walls are made by pouring readymix into wall-shaped forms usually made of wood. Once the concrete has set the forms are removed.
ICF the forms are made of polystyrene, either as separate blocks or panels which are assembled on site. They’re designed to clip together, like giant Lego bricks, so building a wall is literally child’s play.
Once a storey has been finished, reinforcing steel rods are inserted, the forms are filled with ready mixed concrete, the concrete sets and that’s that. The forms stay where they are, creating permanent and very effective insulation, inside and out. You then move onto the next storey.
The forms come in a variety of shapes and thicknesses to accommodate virtually any design. Typically they are covered on the outside with a polymer render which is flexible so it won’t crack, though you can add brickwork or brick slip cladding.
As well as being exceptionally energy efficient, ICF has excellent acoustic properties. I know one selfbuilding couple who chose the system because they wanted to accommodate both a music room and an elderly relative who was very sensitive to noise.
The one skill that is essential for ICF, however, is expert concrete pouring, which is usually done with a pump. Get it wrong and the concrete could end up distorting the forms or even bursting through them. So look for a concrete pump operator who’s used the system before.
But if all this sounds a little hi-tech, there’s another formwork system which is equally hands-on but demands even fewer skills. Durosil lays claim to be the original ICF system. It was invented in Switzerland in 1937 but only reached here in 2008.
It’s an interlocking block but instead of plastic it’s made of a kind of fossilized wood. Essentially it’s wood waste which has been soaked in a solution of pure cement dust.
The result is a block that’s as thermally efficient as timber but as strong as concrete only lighter. You can cut it like timber and suspend heavy objects from it using only woodscrews.
Inside it has two hollow spaces, an inner-facing one where the concrete is poured and an outer one filled with polyurethane insulation. The concrete can be poured by pump or by hand and because of the porous nature of the material a very runny mixture can be used. That means pouring can take place in low temperatures that would halt conventional block and brick laying.
Finally, if you’re committed to the idea of a house built of baked clay but you want to save time on bricklaying, there’s an alternative that’s been popular in Europe for many years. It’s called honeycomb clay blockwork.
The blocks slot together end to end, so that they only need to be fixed to each other horizontally. The fixing is done with a thin, glue-like mortar which is applied with a hand-held machine, requiring minimal skill.
It’s a fast, virtually dry system and the blocks can be filled with insulation for maximum energy efficiency.
If you want to see how effective it can be go to the Prince’s Foundation website which features a house the Foundation built using this method at the British Research Establishment in Hertfordshire. There’s a video tour with Kirstie Allsop.
Honeycomb clay blockwork is mainly being pushed in this country by the brickmakers Wienerberger with their Porotherm system.
One useful advantage of many alternative building methods is that the manufacturers are keen to show off their products and will offer free demonstrations to potential customers. Durosil, for example, organise a number of training days throughout the country, giving you the chance to try out the system for yourself.
Nudura, who manufacture insulated concrete formworks, insist that customers attend a one-day training course and observe concrete pouring on an actual site.
The Structural Timber Association also offer free factory visits to see how different types of timber frame are constructed.
All the systems I’ve talked about so far have all the necessary certification required by building control, so you shouldn’t have any trouble getting approval.
If you do, there are around 60 independent approved inspectors who, in my experience, tend to be more flexible with non-traditional systems.
What I haven’t mentioned is pricing, except to say that on material costs alone all these systems are likely to be more expensive than brick and block. But it’s important to remember that material costs are only part of your overall budget.
The extra you pay on it could easily be recouped by savings elsewhere – on labour, on scaffolding, equipment hire, foundations and on the interest you pay on short-term borrowing. You really need to look at the big picture to judge these systems fairly.
Finally, the golden rule on any non-traditional system is to find a contractor, and ideally an architect or designer, who’s used it before and is enthusiastic about it. Don’t assume a run-of-the-mill jobbing builder can simply pick it up.
You really don’t want them to make beginner’s mistakes with you. But it’s much more likely that they either won’t take on the work or they’ll simply whack up the price.
I’ve only had time to touch on the major alternatives, but I hope I’ve wetted your appetite. If you’d like contact details for manufacturers of all the systems I’ve mentioned, I have a list here which you’re welcome to have.
Timber Frame suppliers
Dan-Wood 01242 695 056 www.dan-wood.co.uk
Potton 01767 676 400 www.potton.co.uk
Scandia-Hus 01342 838 060 www.scandia-hus.co.uk
Scotframe 01803 267 680 www.scotframe.co.uk
Structural Insulated Panel suppliers
Kingspan TEK System 01544 386 601 www.kingspanteck.co.uk
SBS Sip Building Systems 0151 420 1404 www.sipbuildingsystems.co.uk
Sips UK 01933 353 501 www.sips.uk.com
Sips Industries 01383 823 995 www.sipsindustries.co.uk
Border Oak 01568 708 752 www.borderoak.com
Carpenter Oak and Woodland 01225 743 089 www.carpenteroakandwoodland.com
Oakwrights 01432 357 733 www.oakwrights.co.uk
Welsh Oak www.welshoakframe.com 01686 688 000.
Insulating Concrete Formwork
Beco Wallform 01652 653 844 www.becowallform.co.uk
Insulating Concrete Formwork Association 01403 701 167 www.icfa.org.uk.
Nudura 01822 890 251 www.nuduraicfs.co.uk
Polysteel Warmerwall 01242 692 335 www.polysteel.co.uk
Durosil 01495 249 400 www.durosiluk.com
Honeycomb clay blockwork
Wienerberger 0161 491 8200
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