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Selfbuild Construction - 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 endeavour to give you the pros and cons for each system so that you can
decide which building system suits your SelfBuild.
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 BuildPlan.
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.
External Appearance
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.
Sound Insulation
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.
Thermal Insulation
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.
Green Issues
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 programmes.
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.
Foundations
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.
Floors
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 ponding.
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.
Walls
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.
Roofs
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.
Below you will find information on the construction process itself. By clicking on the articles you will open up another page with more details about the Self Build Construction process.
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Timber Frame or Traditional Self Build Houses - How is a house constructed
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Selfbuild construction - How long will it take to build for Timber Frame vs Traditional Selfbuild
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Selfbuild House Cost - Timber Frame vs Traditional Selfbuild
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External Walls - How the outside of the house will look when built
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Sound Insulation
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Thermal Insulation
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Green Issues
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Selfbuild Package companies
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House Foundations
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Floors
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Walls
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Roofs
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Windows and Doors
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Selfbuild Specification - Sample spec for a Traditional House Build
