Selfbuilding - Traditional Build or Timber Frame
If you can't decide whether to build your house using timber frame or brick and block, you're not alone. The question of which one to choose is the most frequently asked by aspiring self-builders. We will endeavor to give you the pros and cons for each system so that you can decide which building system suits your
Timber frame and brick and block are the two main forms of house construction in the UK. Both have their advantages and disadvantages, so the method you go for will depend on your own personal preferences.
Whichever type of build route you choose, you can get a very competitive quote from
Selfbuild construction - How are houses built ?
Both timber frame and brick and block houses have an outer skin (usually brick) and a cavity (usually 50mm). Where they differ is in the construction of the inner wall. With a standard timber frame this consists of a waterproof membrane, sheathing board, structural timber frame, vapour barrier and inner lining of plasterboard. The insulation is placed between the timber frame uprights, and its thickness matches the size of the frame (usually 90mm). With standard brick and block, the inner wall consists of aggregate block and an inner lining of plaster. The insulation is placed directly in the cavity, which is either partially or completely filled.
The main difference between the two types of construction is how the loads of the house are taken. With timber frame, the frame itself supports the weight of the house, while with brick and block, both the outer brick and the inner block take the weight.
The internal walls and floors also vary in construction. With timber frame, dividing walls are plasterboard stud partitions, and floors are typically of timber construction (although ground floors can be concrete). With brick and block, dividing walls are usually solid block, and the floors are typically of solid beam and block construction.
A range of outer claddings can be applied to both timber frame and brick and block houses, including brick, stone, render, hanging tile and timber boarding. With timber frame the actual timber structure is often exposed as a design feature.
Windows in timber frame houses are fixed to the inner timber frame, rather than to the brick outer skin, which results in a deeper external sill. This feature helps to distinguish between the two types of construction from the outside.
With timber frame the option exists to expose the timber ceiling beams for a Cathedral-style look. These are particularly common in Scandinavian house designs. Some timber frame suppliers build post and beam houses. Here, vertical posts (as well as horizontal beams) form an integral part of the structure and character.
With brick and block, dummy timber posts and beams can be added to masonry walls. These are not structural, but can look just as authentic.
With timber frame, only dry-lined plasterboard can be used for the walls and the ceilings, while with brick and block, wet plaster can also be used. With dry-lined plasterboard, wallpaper can be put up immediately, whereas with wet plaster you have to wait six months. Dry-lined plasterboard walls can sound hollow when you tap them, while wet plaster on masonry walls makes for an all-round heavier, more solid structure.
Weight is important to good sound insulation - remember sound waves are vibrations, and it is hard to vibrate a heavy wall. Solid bult walls offer an obvious advantage here, while lightweight plasterboard-finished walls require more care. Sound insulation can only be improved by suspending mineral fibre between the stud partitions, which will absorb some of the sound.
Although solid walls gives good resilience against airborne sound, such as music and voices, it offers little in resistance to impact sound, such as footsteps. Concrete floors are particularly prone to impact sounds, but laying a resilient layer, such as a carpet, onto the floor will guard against this.
Isolating two structures is also important for good sound insulation, as it breaks the sound path. Cavity walls in both house types perform this function. Floors constructions can also be isolated with the use of a floating floor system. The two parts are separated by mineral wool, which gives resistance to both impact and airborne sound. A timber floor construction is lighter than a concrete floor, so to achieve the same levels of sound insulation, additional layers of board can be fitted to increase the total weight.
An airtight structure is also important for good sound insulation. It is pointless spending money on sound insulating either a timber frame or brick and block house, if the sound can pass around a partition via an poorly sealed window, door or service duct.
Both timber frame and brick and block houses have to comply with energy efficiency targets set out by the Building Regulations. The minimum U-value (insulation level for each component of the build) required for exposed walls is 0.45 W/m2K.
A standard brick and block house offers a U-value of 0.43 W/m2K. Whereas a standard timber frame outperforms the mandatory ratings, achieving a U-value of 0.41 W/m2K. The latter can be improved to 0.29 W/m2K by increasing the frame size from 90mm (standard) to 140mm (enhanced), which increases the space for insulation. This gain is at comparatively little extra cost.
For brick and block to match the same levels of thermal insulation achieved by an enhanced timber frame, insulated dry-lining with vapour check has to be included in the wall construction, increasing costs considerably.
Timber frame selfbuilds are lightweight, have little thermal mass and the insulation is close to the inside of the house. The combination means that they respond quickly to changes in temperature, so when the heating is switched on, the house heats up quickly, and when the heating is switched off, the house cools down quickly.
Brick and block selfbuilds are heavy, with a high thermal mass. When the heating is switched on, the plaster and inner block slowly absorbs the heat. Although the house takes longer to warm up, it also takes longer to cool down once the heating is turned off. Brick and block is therefore a good choice for families with someone at home for most of the day, while timber frame is suited to families who are out for most of the day.
As long as the same wall, floor and roof insulation levels are specified, there will be no difference in the overall energy usage between timber frame and brick and block. This is only one part of creating an energy efficient house, with windows, doors, and heating specification playing an increasing important part.
Selfbuild construction - how long will it take to build ?
It is generally accepted that a timber frame house is quicker to construct than a brick and block house. In good conditions, a timber frame house can be built in around 12 weeks, and a brick and block house in 18 weeks.
A timber frame house is usually wind and watertight by week five of the build, so while the bricklayers work on the outside, work can begin on the internals. By contrast, a brick and block house is not normally wind and watertight until around week nine or 10, so work on the inside starts later in the build
programme. This is slowly improving with several block manufacturers developing systems that make it possible to build a house up to first floor level in a day.
Build timetables can be misleading, as many don't take into account the time it takes to order and manufacture a timber frame kit.
Good organisation and site management ultimately influences the build time. There is no benefit in having a wind and watertight shell built in under a week if the first fix plumber and electrician is not available to start work. Package companies and architects are happy to offer advice on pre-planning and placing orders, to ensure that a build goes as smoothly as possible - whatever method of construction is used.
Timber Frame training and backup
In the past, architects, builders and tradesmen received little training in timber frame construction. Today, while the majority are still more familiar with the techniques required for brick and block, attitudes are changing. Many timber frame package companies offer plenty of support, introducing their customers to local builders with plenty of experience in timber frame house construction.
Cost - Timber frame vs traditional selfbuild
Representatives of both timber frame and brick and block agree that there are no measurable differences in cost between the two constructions if designed to minimum Building Regulations standards. What ultimately determines build costs are individual specifications, build route, labour and plot details.
If high thermal insulation standards are specified, timber frame can be significantly cheaper, whereas if good sound insulation is a priority, then brick and block is easier on the finances.
If timber frame is chosen for its quick build time, savings can be made on the interest on money borrowed for building, storage and rented accommodation. That said, with timber frame a large amount of money is required earlier on in the project to pay the kit manufacturer. With brick and block, build costs are spread over a longer period of time.
Whatever method of construction decided upon, the Accelerator mortgage can help with finances and cash flow during the build, by providing funds at the beginning of each stage, rather than the end. This is especially important for timber frame build as you will need to pay for the timber frame before it is delivered.
With growing concern for the environment and global warming, it is in everyones' interests to keep energy demands as low as possible.
Building energy efficient, well-insulated homes to reduce fuel consumption and running costs is essential. However, what many self-builders do not realise is that even before a house is built, the materials used in its construction have a Product Energy Requirement (or PER), which refers to all the energy (expressed in kilowatt-hours) that goes into producing and transporting a product.
Timber has the advantage here as it is produced by natural means - sun, water and air, so its energy requirements are all in the extraction and transportation of the logs from the forest.
A timber frame wall in a typical three-bedroom detached family house has a PRE of around 7,450kWh, while a concrete block wall in the same property requires 1.7 times more energy, with a PRE of around 12,816 kWh.
Timber is also the only renewable structural building material available, and the majority of timber frame package companies invest heavily in well-managed replanting
Selfbuild Package companies
As well as helping with the construction of your home, a package company can also help in its design. Some will also assist with finding land and overcoming planning problems. The majority of package companies build in timber frame, although there are a few that build in brick and block. A complete package can be offered by Buildplan send us your drawings and we will prepare a detailed bill of quantities, costed very keenly. We can get some very good building material discounts because of the amount of selfbuilds that we supply materials for. Buildplan is now treated as a large house builder and the discounts reflect this.
Prices, quality of product and customer care all vary, so it is worth speaking to three or four companies before making a choice. If you invite someone from a company to visit your site be careful about what you may inadvertently be agreeing to. A contract will involve a major financial commitment, so get a solicitor to vet it first before you sign anything.
Whether you are building in timber frame or brick and block, you will need to pay the same attention to the foundations and groundwork. There are four main kinds of foundation to consider:- strip foundations, trenchfill foundations, raft foundations and piled foundations. Strip and trenchfill are the most common types, while raft and piled are reinforced foundations used for more difficult sites.
Strip foundations consist of trenches partially filled with concrete and then built up to ground level by bricks or blocks. Trenchfill foundations, on the other hand, are almost entirely filled with concrete, and while the extra depth adds to the concrete costs, it can save time and
labour. Deep trenchfill foundations are indicated where the house is built next to trees.
Raft foundations consist of re-inforced slab sitting under the surface. Here the weight of the house is spread over a wide area on the ground below. This means that if any settlement occurs, it is unable to affect any one part of the above structure. Raft foundations are usually used on difficult, variable ground, such as by a river. Piled foundations will be specified where you need to dig down some way to find good load-bearing ground. Here, holes are bored through the bad ground and into the solid, and then filled with concrete. The result are
'stilits' which provide a grid on which the house can be supported.
The design and construction of the ground floor will largely be determined by the ground conditions. There are three main types of ground floor construction: traditional ground supported concrete floors, suspended timber floors and pre-cast concrete beam and block floors.
Traditional ground supported concrete floors consist of a compacted hardcore base on to which is laid the flooring slab and insulation. Such floors are a popular choice for normal level sites.
Pre-cast beam and block floors are now rapidly growing in popularity. It completely avoids the costs of compacting and backfilling the hardcore to receive the concrete, providing a sound working platform once the beams and blocks are in position. Thermal insulation is placed between the beam and block and finished floor surface. The ground level beneath the floor should be raised to that of the outside ground level to prevent water
In the case of difficult ground conditions, such as slopes, clay soils etc. a suspended floor will be required. Timber is used here, as wood is very versatile and allows for some ground movement. Suspended timber floor construction is also the preferred choice for first floors.
Flooring on both ground and first floors may be part of the first fix carpentry, or you may to prefer to screed the ground floor. If your walls will be
drylined, it is important to let the screed dry out first. Screed provides a smooth surface on to which you can lay carpets, tiles, timber floor covering etc. Screed is also the best covering for underfloor heating, which should be planned well in advance of your floor construction.
Whether you are building in timber frame or brick and block you will need an outer wall. This is usually brick, although stone, render, hanging tile and timber boarding are other options also worth considering.
Bricks can be bought from large DIY stores, builders merchants, specialist brick merchants and direct from brick manufacturers. Based on your detailed house plans, a builder's merchant or quantity surveyor will be able to work out how many bricks you will need and how much this will cost. As a rough guide, a 2,000 sq ft house will require 14,000 bricks, at a cost between £140 and £500 per thousand bricks.
Bricks are usually made of clay, which varies in colour and mineral content from region to region. In an architecturally sensitive area, the planning officer may insist you use bricks made from local clay. Concrete bricks and calcium silicate bricks are other options available.
Just as important as your choice of brick is your choice or mortar. As well as affecting the appearance of your home, the mortar will determine the compressive strength of the brickwork. A cement rich mortar (1:5 Portland cement / sand mixture) is very strong, although the same strength can be achieved with a lime-based mortar (1:2 lime / sand mortar). Lime mortars have the benefit of rendering all bricks reclaimable in the future.
If you plan to use salvaged bricks, then for reasons of durability, it is important that you use a mortar that is as weak as the mortar in the wall from which they came. Reclaimed bricks will give your new build an instant aged appearance, as will handmade bricks. Mechanisation in the late nineteenth century lead to large machine made brick manufacturers, although the demand for individuality and character has meant that handmade brick production has started to grow again.
While most of us will spend weeks searching for the right materials for the external walls, materials to construct the internal walls tend not to get the same attention, although they should.
In timber frame houses walls will invariably be drylined with plasterboard, whereas with brick and block the inner wall usually consists of concrete block and a lining of plaster, although drylining and plasterboard is also an option. Drylined plasterboard walls can be decorated immediately, but may sound hollow when you tap them. Wet plastered masonry walls make for an all-round heavier structure, which improves sound insulation, although the plaster has to be left for six months to dry out before decoration.
With timber frame, wall insulation goes behind the plasterboard, between the timber uprights. These walls tend to enjoy better thermal insulation as the insulating material match the size of the frame itself, which is 90mm as standard. With brick and block, insulation is placed in the cavity between the outer and inner wall, and this is 50mm as standard. This can be increased, but often at great expense.
The prime purpose of any roof is that it should be weather-proof, but for many self-builders the most critical question is whether it should be of trussed rafter construction or traditionally framed.
Trussed rafters consist of prefabricated units, which are quicker to erect and easier on the finances, although they limit the amount of usable space in the loft. If you want a room in the roof, then specify a traditionally framed roof. This will be erected on site by a skilled craftsman and as such will take more time to build and be more expensive.
The choice of roof covering (clay tiles, natural slate, concrete, copper, turf or thatch) will influence the pitch and design of the roof, which must be designed to shed water as quickly as possible. For example, with a thatched roof you are likely to be advised against the use of dormer windows as the low pitch surrounding such constructions will leave the straw / reed wet and therefore decay more quickly. If your roof design includes hips, valleys etc. then you will have to use a smaller tile to give your architect / builder greater flexibility.
If you are building in an architecturally sensitive area, the planning officer may insist you use whichever material predominates in the area. If you are converting an existing building, like an old barn, it may be possible to salvage the roof covering and match it with slates from a local reclamation yard. This is usually only available in small batches, so if you are working on a larger project consider using reconstructed stone - made from concrete poured into a mould taken from original stone.
There are hundreds of different tiles and slates to choose from today. These can be bought from builders' merchants or direct from manufacturers, who will provide a minimum specification of their product (the lap, pitch, degree of exposure etc.)
Based on your detailed house plans, a builder's merchant, manufacturers or quantity surveyor will be able to work out how many tiles you will need and how much this will cost. You will also have to budget for the fittings and accessories, such as ventilation products to comply with building regulations.
Once you have decided on what sort of roof you want and the materials you will be using, contact the National Federation of Roofing Contractors (Tel. 020 7436 0387). The NFRC can put you in touch with an approved roofing contractor in your area with experience in working on similar roofs to the one you are planning to build.
Windows and doors
The right choice of windows and doors can not only improve the appearance of your new home, but also its insulation and security.
Windows are generally made from one of the following materials: timber (softwood or hardwood), aluminium or plastic (PVC-U). Softwood is the cheapest option, however it will soon deteriorate if not painted regularly and also tends to warp with changes of temperature. Hardwood is far more durable and also offers good thermal insulation. It also needs regular maintenance, but one coat of preservative woodstain makes this an easier task than painting. Hardwood is expensive and can cost the same as top quality PVC-U. Aluminium is the strongest maintenance-free window material, but as on its own is a poor insulator, so most manufacturers offer some sort of thermal barrier (like thin PVC-U) to help prevent condensation forming on the frames. PVC-U frames come in white and in wood-grain finish, but unlike wood you don't have to paint them.
Just as important as the frames is your choice of glass as this can help reduce heat loss and improve energy efficiency. With standard double-glazing, the air in the cavity between the two layers of glazing acts as an insulator. Replacing the air with an insulating gas like Argon or Krypton will increase thermal performance. Coat the glass facing the inside with a reflective coating and this is improved even more. If over-heating is a concern, then specify glass with a coating on the inside so the sun's rays are reflected back. To improve sound insulation increase the size of the cavity between the two panes of glass. Triple glazing can also help here, as the extra weight of the window will reduce sound vibrations. Remember: glass is not only for looking through - but looking at. Why not go for stained glass for some of the windows in your new home?
With front doors, hardwood is the most popular choice, although other material options like glazed PVC-u composite doors and steel doors benefit from being very secure and virtually maintenance-free, and can, if you choose, be made to appear like wood. Internal doors are usually made from softwoods. To increase the sense of light in your home consider using glazed internal doors too. Save space by choosing sliding or folding doors around the home.