STRUCTURAL SYSTEMS FOR BEGINNERS
Dipping your toe into the world of self building for the first time? Rebecca Foster rounds up the best construction methods available for your bespoke project
Discover which build method is right for your project with Rebecca Foster’s in-depth guide to the options
Choosing the structural system for your home is one of the biggest decisions you’ll make during your self build journey. Not only will it shape the result of the project and how the house performs upon completion, but it’ll also inform the twists and turns of the build process along the way. A lot depends on your overall objectives for the project and how you want to live in the finished abode. “Your choice could be influenced by factors such as location – a tight site, for instance, may not offer delivery options for large prefab structural walling,” says Johnny Lovett, director at Parkwood Builders. “Also, thermal efficiency requirements, planning limitations and budget constraints will come into play.”
Every build method comes with its own set of pros and cons, so it’s important to do your research before diving in. For newbies to the self build world, there will be additional factors to bear in mind. For example, is there an option that will give you leeway to make design changes on site? Which route allows you to load most of the heavy lifting onto the supplier? Here, I review the options from a beginner’s perspective.
Brick & block
This tried and tested method has plenty of pros for first-timers. Cavity wall construction is the conventional route – typically with an inner layer of blockwork, built up in courses, with an outer leaf of brickwork. The space left between the inner and outer face is filled with insulation for good thermal performance. If you’re new to self build, one plus is that there’s many experienced contractors in the UK who can handle a brick and block build. It shouldn’t be difficult to get multiple recommendations for a firm you can rely on. “The works that take place post-construction are straightforward to manage with regards to trades and materials compared to some alternative systems,” says Johnny. Working with smaller construction units (bricks) comes with some some benefits compared to larger, prefabricated components made to specific dimensions offsite, too. The build-up of the structural shell is slower, allowing self builders more time and space to make design tweaks (and order last-minute materials) as the house evolves – this is not always viable if you’re erecting a timber frame that’s been made to match your foundations down the last millimetre.
There are a few things to bear in mind. “All the walls must be checked to confirm they are level and plumb, ensuring the required dimensions are being achieved once construction progresses,” says Johnny. “This is the key for brick and block. The walls are built up using a combination of materials, which means greater risk for discrepancies and error in the setting out and construction.” That’s why it’s so important to work with a contractor you can trust will do a good job. Ask to see examples of your builder’s past projects so you can assess the quality of the workmanship.
Oak frame
The chance to design something unique is what attracts many self builders to creating a one-off home – and the characterful beauty of oak certainly enables you to do that. Though this kind of timber is considered a premium material, it doesn’t mean an oak frame abode is out of reach for your first project. In fact, working with an experienced supplier who can hold your hand from design phase to completion paves the way for a smooth process.
With this type of post and beam construction, the oak frame is erected and then sealed in an efficient thermal envelope. Some people use SIPS to wrap the structural skeleton, while other suppliers have their own solutions, like Oakwrights’ Wrightwall Natural encapsulation system. Individuals can choose from a sliding scale of services depending on how much they want to be involved, and how much they’d prefer to hand over to the supplier. “The basic package includes the architectural design, Building Regulations and the oak frame, encapsulation system and glazing supplied to site and erected,” says Tim Crump, founder of Oakwrights. “The full service would carry you all the way through design to full project management of your completed scheme. So, you can take on as much or as little as your ability and budget allow.”
As with any construction system that involves a degree of prefabrication, there are lots of decisions to be made upfront, with less scope for making changes later. But to some extent, this will be the case with other build methods, too. “And no matter what system you choose, the more planning and early decision making you do, the smoother the build process once you get started,” says Tim.
Make sure you appoint a designer who has plenty of experience working with oak frame – most suppliers have their own in-house team. Green oak settles and shrinks as part of the natural drying process, which needs to be factored into the plans. There are certain design decisions you can make to keep the process straightforward, too. “Use an uncomplicated aisled oak frame with an up and over roof. The rectangular bay structure gives beauty and cost efficiency through its simplicity,” says Tim.
Timber frame
Broadly speaking, this method can be divided into two categories: closed- and open-panel. The walling elements for both systems comprise structural studs enveloped in wood-based sheathing (usually oriented strandboard) and packed with insulation. The components are made in your supplier’s factory to an exact set of specifications from your designer. While they’re being made, you can get on with clearing the plot, putting in your foundations etc. Open-panel arrangements are left open on one side so that insulation, services and windows can be fitted on site. Closed panel setups have the insulation and possibly more fitted in the factory, prior to delivery.
“Timber frame systems often come as part of a turnkey service, which is a major benefit for those who are not familiar with the process of building a house from scratch,” says Rhys Denbigh, director at Facit Homes. This option means that once the design has been finalised, you can hand the bulk of the responsibility (and stress!) to your supplier so they can look after the planning application, Building Regs, construction and project management. This route also offers cost certainty, as you’ll agree on a figure at the outset of the build. Of course, it does usually come with a bigger price tag attached, as you’re paying for your supplier to take on most of the heavy lifting on your behalf.
But that doesn’t mean timber frame doesn’t offer scope for beginners to get more involved in the process. “Our clients can choose an assisted self finish option. This allows them to complete the interior themselves,” says Rhys. “We take care of the foundations, timber frame, cladding, first fix plumbing and electrics, then we support them as they complete the interior.” There are also options such as structural design and shell build, which will see the supplier manufacture and erect your frame on site to weathertight stage, ready for you to take forward with your own trades or main contractor. This gives you the security of knowing the core structure of your home is being completed to an agreed budget by a single company.
As with other prefab setups, newbies may be concerned about the number of design decisions that need to be made before the panels go onto the production line. “Though
not impossible, it’s not advised to make changes to the internal layout once the final design has been approved and the production of the structure is underway,” says Rhys. Revisions at this stage will likely add to costs.
SIPS
Like timber and oak frame, SIPS (structural insulated panels) offer all the advantages of prefabricated building techniques: certainty over cost, timescales and finished performance. The system comprises strong, energyefficient panels, typically made from wood-based boards that sandwich a layer of rigid insulation. Structural components are made in your chosen supplier’s factory, giving you the opportunity to prepare the plot.
“Due to the amount of fabrication work done off-site, the kit is erected quickly,” says Derek Mcintyre, commercial manager at JML SIPS Low Energy Homes. Reaching weathertight within two to three weeks gives newbies an advantage from a project management perspective, as it’s possible to line up follow-on trades early, thanks to certainty around your build programme. Getting contractors booked in promptly can save hassle later on – a definite plus if you’re project managing a self build for the first time.
“The SIPS company usually carries out the structural engineering design as part of the service. Some suppliers, like us, offer the full erection of the kit as part of the package,” says Derek. “This ensures it is put up correctly and negates the need for the individual to deal with this element of the build.” As with timber frame, once the panels are slotted into place, changes are tricky and potentially costly. Therefore, you’ll find yourself with the majority of decisions stacked towards the early phases of the project.
“Building with SIPS shouldn’t provide any difficulties for beginners, provided the kit is sourced from an accredited supplier,” says Derek. “The Structural Timber Association (STA) is the main body representing system manufacturers and you should therefore ensure your supplier is a member of their Assure rating system.”
It’s smart to appoint a designer who is well versed in the unique features of SIPS. “It’s also worth appointing your supplier as early in the design process as possible to ensure they can work effectively with the architect,” says Derek. “This avoids wasted time, as there’s no danger of the architect putting together the plans to different panel thicknesses, for instance, or other system details.”
ICF
Insulated concrete formwork comprises a series of interlocking hollow blocks, typically made of expanded polystyrene with a central web of metal or plastic fasteners. Once stacked, reinforced and braced, the walls are filled with concrete - creating a strong, pre-insulated structural shell. Once in place, the interlocking walls are filled with concrete. “For newcomers to self build, ICF has instant appeal because the building process is relatively practical and straightforward, using materials that are well known and proven in construction over a long period of time,” says Robin Miller, managing director at Beco Wallform.
There’s plenty of design flexibility – another boon if you want a home with wow factor. But it’s vital that everyone in your architectural team is familiar with working with ICF. “These structures need the expertise of a structural engineer – their advice is crucial,” says Jon Rowlands, sales director at Jackon. “If you think your engineer is overspecifying, seek advice from another expert. Don’t ignore or dismiss their advice without a qualified reason.”
For those who want to get hands-on, ICF is ideal – many suppliers run training courses for self builders. “Always choose a system that runs approved courses either on site or in the classroom. Follow the guidance provided, then the finished product will provide a robust, low-energy home with an exceptional lifespan,” says Jon.
There are numerous ICF systems available, so do your research to make sure you choose the right solution for your project. “There’s flat-packed to pre-formed to full panel systems. There’s also a range of options in terms of cost, performance and ease of construction, says Robin. “The Insulated Concrete Formwork Association (ICFA) is a good point of reference, as it ensures standards are maintained and proper training and support is provided.”
Your builder should triple-check everything is correct before the concrete pour happens, as it can be time consuming to rectify mistakes later. Opting for several smaller pours rather than a single large one may be a wise move. “One large concrete pour rather than two more manageable pours will save on pump hire costs – but it puts a lot more pressure on those involved,” says Robin.