Guide to Building Techniques

Numerous building techniques are available, and selecting the most suitable one will depend on your budget, the requirements of planning approval, and your design preferences.

BRICK AND BLOCK CONSTRUCTION

In contemporary conventional homes, the construction of walls involves two layers. An internal wall made of blockwork is paired with an external wall, built from either brick or stone.

These walls, along with certain internal dividers made of blockwork, form the supporting structure of the house.

Construction using brick and block is among the most economical methods. As most builders favor masonry, it tends to be priced more competitively. Additionally, many 'self-builders' are industry professionals, meaning they have access to better rates from their network, compared to prices from a timber frame company.

However, compared to frame construction, modern masonry takes longer to complete.

TIMBER FRAME SYSTEMS

Open-Panel Open-panel timber frame systems consist of structural panels that form the internal, load-bearing layer of the outer wall. These panels comprise studs, rails, a single layer of sheathing, and a breather membrane. The system is crafted from treated softwood timber framing, over which either Ply or OSB board is attached as a structural sheet material. The system can achieve U-values from 0.26 down to 0.15 W/m²K, depending on its design.

Closed-Panel

Closed-panel systems are composed of studs, rails, insulation, and sheathings or linings on the panel faces. These systems also include a vapor barrier on the insulation's warm side and a breather membrane on the panel's outer face. For easier installation and construction, closed panels may come with pre-fitted windows and internal service zone battens. They can achieve U-values from 0.25 to 0.10 W/m²K, making them excellent for modern energy-efficient homes.

INSULATED CONCRETE FORMEWORK (ICF)

Insulating Concrete Formwork (ICF), also known as Permanently Insulated Formwork (PIF), is an in-situ concrete construction system with built-in insulation, facilitating rapid construction of insulated walls for homes.

ICF utilizes hollow, lightweight block components that interlock without the need for intermediate bedding materials like mortar. The blocks consist of insulation sheets, typically expanded polystyrene, interconnected with plastic or steel ties or an integral web of the same insulation material.

Once the concrete sets, it results in a high-strength concrete frame structure, while the formwork remains in place as thermal insulation. This system can achieve U-values from the standard Building Regulations requirement of 0.3 W/m²K down to 0.11 W/m²K, making it suitable for zero-energy buildings.

Don't forget to check if you need approval before starting any new build or extension

STEEL FRAMED CONSTRUCTION

Steel construction, a popular method in the USA and South Africa, has been gaining interest locally. The steel framework is light, robust, weather-resistant, and quick to erect. Exterior panels are secured to the steel frame and subsequently rendered. With most materials being pre-cut before site delivery, houses can be made weatherproof in a short span of time.

STRUCTURAL INSULATED PANELS (SIPs)

Structural Insulated Panels (SIPs) are a cost-efficient, eco-friendly, and labor-saving alternative to conventional construction methods such as timber framing and masonry.

Typically, a SIP consists of two layers of Oriented Strand Board (OSB) enclosing a substantial layer of high-grade foam insulation. This insulation, commonly expanded polystyrene, is inserted between the OSB layers under pressure, forming an 'autohesive' bond. As the foam solidifies, it chemically adheres to the OSB, yielding a light yet robust panel that requires no internal studwork.

With a quick assembly time (usually 5-7 days for a standard house, including the roof), superior strength, and excellent energy efficiency, SIPs offer an exceptional choice for self-builders. Precise manufacturing of these panels simplifies on-site construction, lessening the likelihood of project delays. These panels are typically used in building roofs and exterior walls, though they can also be utilized for floors and interior walls.

Long-term benefits of using SIPs include lower energy bills and decreased energy use and CO2 emissions. Their light weight and factory production methods diminish transportation energy and on-site waste, further minimizing the overall carbon footprint.

COB CONSTRUCTION

Creating structures with earth is a concept nearly as old as human history. In England, traditional cob materials comprised clay-based soil mixed with water and straw, sometimes with the addition of crushed flint or sand.

Despite its simplicity, cob is extremely resilient, as evidenced by the oldest existing cob structure in the UK, built in the 1200s.

Construction Method

The process involves the gradual building of thick walls in layers, allowing each layer to solidify before applying the next. The wall is then coated with clay or lime, or left in its natural state.

Cob construction is straightforward, economical, and requires minimal tools beyond one's hands, making it a highly eco-friendly option. The final product dries to a hardness comparable to concrete, making it suitable for load-bearing walls. It is long-lasting, fire-resistant, provides excellent insulation, and is malleable, enabling the creation of walls in any desired shape. However, the construction process can be quite time-intensive.

STRAW BALE CONSTRUCTION

Straw, grass, or reed has been used as building materials throughout history, mainly due to their low cost and wide availability. The necessity of the late 1800s on the American plains, where lumber for construction was scarce, saw the emergence of straw bale houses. Recently, a resurgence in straw bale construction has occurred due to increased interest in sustainable housing.

Straw, often an agricultural surplus product, is not only cheap (roughly 40p a bale, or £1.50 delivered) but also a readily renewable resource. If constructed properly, houses made of straw bale are fire-resistant, waterproof, and surprisingly free from pests, with high-insulation walls.

Construction Methods Structural Bale Construction. For load-bearing purposes, the bales are stacked on top of each other in a stretcher or running bond, secured with long wooden pegs driven through to connect the layers.

NON-STRUCTURAL / INFILL SYSTEM

When utilized for insulation, the bales are used to fill the walls of a timber frame structure. In both scenarios, the walls are coated with lime due to its ability to handle minor movement in the bales.

Construction Basics

Approximately 300 standard three-wire bales of straw are required to construct a 2,000 sq ft house (186 sq m).

The bales should be uniform in size (around a meter long and half a meter wide), securely bound with two strings, and should have very few seed heads. They should be properly compacted, dense (each bale weighing between 16-30 kilos), and dry. It's crucial to keep the bales dry during construction and ensure the center of the bales remains dry even after construction. If the exterior gets wet, it's acceptable as it will naturally dry out.

Maintenance

Theoretically, a well-built straw house, situated in a location with good drainage, could last for centuries. However, a more permanent material should likely be used for the roof, and the roof should be constructed at a steep angle for effective drainage.

Read about the Renders available for the exterior of your house.