The starting point for many a self-build project is how the home will be made, not least because it will have a major effect on the bottom line-the cost.
Choosing a construction method depends on many things, cost being a major one, although the experts at the National Self Build & Renovation Centre suggest it is perhaps more relevant to consider the following: the amount of work you intend to do yourself, which will have a knock-on effect on how much money you have to spend; how quickly you want to build – particularly relevant if you are in rented accommodation while working on your project; whether you are project managing yourself, in which case you might want to lighten your load by increasing the level of off-site manufacture; and when you are starting your build – winter isn’t ideal for masonry work. To help you choose the best method for your project, we’ve rounded up the pros and cons of the various options.
1 Steel frame
Structural system with steel columns, beams and girders.
Advantages Good energy efficiency and acoustic standards can be achieved; suitable for buildings with large, open-plan spaces.
Considerations Because of exacting manufacturing standards it is not always perceived to be as flexible as other construction methods. It’s necessary to wrap the exterior of the frame with a rigid insulation layer to prevent heat loss, with additional insulation then placed between the studs; at the moment few companies deal with one-off houses, although this is expected to change.
Costs The price of steel means you should expect costs to be around 25 per cent more than a comparable timber frame.
2 Brick and block construction
The most common building method – bricks are attached to an inner skin of blocks.
Advantages A quick construction method, with blocks being lightweight and easy to use.
Considerations Aerated blocks are good insulators, although a normal sized one won’t meet current energy efficiency regulations, so you will need additional insulation. You may also want to use a 150mm thick block (normal thickness is 100mm). Different blocks can take different loads, so it’s important to understand where to use ones with greater strength. Heavy rain and frost present the biggest risk to brick and block work, in terms of performance and appearance. Such weather conditions can force work to stop, and can also significantly extend time required for drying out, all of which increase costs.
3 Pre-cast concrete panels
Concrete panels prefabricated off site in a formwork mould.
Advantages This method provides an exceptionally strong building, and is suitable for basements, as long as an effective waterproofing system is used.
Considerations Best suited to volume house building, where a high degree of repetition is involved; relatively uncommon for the construction of a one-off house as heavy plant and plenty of space is needed to put the panels in place.
4 Timber frame
Timber frame Timber studs and panels can be clad in virtually any weatherproof material. Engineered structural beams are increasingly available, which enable a greater span to be achieved, offering better flexibility for ground-floor room layouts.
Advantages Flexible system suitable for almost any design; quick to build on site, creating an almost weatherproof shell generally within a couple of weeks, thus allowing internal works to progress sooner. A renewable source of construction, with good energy efficiency when teamed with appropriate insulation – important when taking into account the Code for Sustainable Homes (planningportal.gov.uk).
Considerations Has a reputation for poor acoustic qualities between storeys and rooms, but this can be improved with modern methods of construction and insulation.
Keeping an eye on costs
Build costs vary dramatically, but Joe Martin, executive director of the Building Cost Information Service (BCIS) (020 7695 1500; bcis.co.uk) says £1,200 per sqm (which allows 20 per cent for contingency costs) is a good average figure for self- builders to keep in mind. ‘The costs are in making your design unusual and in changing your mind,’ he says.
You should also factor in external works, such as landscaping, which can increase your budget significantly, and don’t forget about miscellaneous costs such as planning applications, building regulations inspections and connecting to utilities.
The Property Makeover Price Guide (bcis.co.uk) has good advice, particularly on hiring, managing and paying contractors. Key points include speaking to previous clients and acting on recommendations, agreeing a payment schedule, agreeing the cost of any changes before they are done and entering into a formal contract – the Joint Contracts Tribunal (0845 082 1080; jctcontracts.com) and Federation of Master Builders (0870 1620 0947; findabuilder.co.uk) have standard ones you can use. RICS also runs a find-a-surveyor service (0870 333 1600; ricsfirms.com) – speaking to one can help you gauge costs.
5 Insulated concrete formwork (ICF)
Hollow polystyrene blocks are assembled on site, then the internal cavity is filled with ready-mixed concrete for strength, so you end up with a concrete external wall wrapped on both sides with a good layer of polystyrene insulation.
Advantages This is a quick construction method, and well placed to meet current and future building regulations, with no need for additional insulation inside. It is also well suited to self-builders.
Considerations You’ll need to master a few techniques for a successful build: a compressed air poker is used to vibrate the ready-mix within the cavity in order to get rid of any voids in the concrete. It’s also important not to pour too quickly, otherwise the blocks will burst. Care has to be taken with the metal ties that hold the polystyrene together before the concrete is inserted, and some external bracing which can be fundamental to the erection.
6 Structural insulated panel system (SIPS)
A traditional cavity wall construction with the inner skin being a structurally insulated panel, faced on both sides with oriented strand board, which carries the weight of the building.
Advantages One of the quickest methods, and very thermally efficient. Very large panels can be constructed, and use far less conventional timber, as structural timbers are not required except at junctions. The panels are craned into position, which makes on- site construction time very short, but remember to bear in mind site access for this. Roofs and floors can also be constructed using SIPS.
Considerations Not so easy to adjust on site if changes need to be made; the panels themselves are more expensive to make, but savings are introduced later in the build as you won’t need much (if any) extra insulation in the walls to meet current standards.
Recommended retailer/useful contacts,
Meisterstueck Haus UK www.meisterstueck.com
Griffnerhaus Ireland www.griffner.com
Lakeland Timber Frame www.lakelandtimberframe.co.uk
Welsh Oak Frame www.welshoakframe.com
Nordic Country Log Homes www.nordiccountryloghomes.com
Stommel Haus www.stommel-haus.co.uk
Lowfield Timber Frames www.lowfieldtimberframes.co.uk
True North Log Homes www.truenorthloghomes.com
Tailor Made Designs www.tailormade-frames.co.uk
Hanse Haus www.hansehaus.co.uk
Simply Selfbuild UK Ltd www.simplyselfbuild.co.uk
Roundwood of Mayfield www.roundwood.com
Words: Luke Tebbutt