Building for longevity

Costs and benefits

With a house designed for adaptability, you can look forward to more space and greater convenience and reduced costs for extensions in the future. Houses that can adapt will be useful longer reducing the future use of resources. Building in adaptability has a present cost but can save money in adaptations and premature obsolescence in the future. Some common sense and relatively inexpensive measures now can save money in the future.

Summary: creating an adaptable house

Adaptability in housing is a necessary precondition of sustainability. Only if homes can adapt to changing needs and expectations will they have a long useful life, thus reducing the waste of resources implied in premature demolition. Adaptability will have to deal with a number of foreseeable trends including rising expectations of space and equipment, the increase in the number of smaller households and greater reliance on electronics in the home.

Building for longevity

Adaptability can be achieved by:

  • Generous space standards
  • Adaptable built forms – terraced houses rather than apartment blocks for instance
  • Providing space for expansion of dwellings
  • Built-in expansion space, in the loft for example
  • Easily modified structural systems such as frames
  • Easily accessible service installations
  • Easily adapted forms of building such as timber construction

There are a number of useful concepts, including separating parts of a building which have different replacement time scales, and in particular separating structure and infill, as is common in office buildings.

The Segal Method

This timber-frame method, devised by the architect Walter Segal in the mid-60s and used successfully for 200 or more self-build houses since built individually or in groups, is a practical example of the separation of the S’s referred to by Stuart Brand. The structure stands on, but is not fixed to, the long-lasting foundations. It provides a long-term framework which is filled in with non-structural wall panels, partitions, windows and doors which can be altered to suit particular needs and wishes. The services are run in voids in the walls, floors and ceilings so that they are accessible and can be modified and renewed as necessary without damaging the fabric of the building.

Segal Method buildings demonstrate one or two general approaches which can improve the adaptability of buildings. So provide accessible service voids and build large span frame structures with non-loadbearing infill.

The method is devised to be economical and quick and relatively straightforward to construct. A Segal building is supported on individual pad foundations which consist of blocks of concrete, commonly 600mm square in plan and 900mm deep, under each post which are spaced around 3-4m apart. These foundations can be hand-dug and there is no need to level the site which eliminates the need for heavy earth-moving which makes the construction straightforward for self-builders.

The post and beam frames are bolted together flat on the ground. The level of the foundations is taken and the posts are cut to length before raising the frames into position. They are braced in position temporarily whilst the roof and floor joists are fixed. A piece of lead is placed between the bottom of the post and the foundation to prevent moisture getting into the end grain of the timber leading to rot.

The infill of readily available, standard building materials; maintenance-free, weatherproof cladding panels on the outside, a finish of plasterboard on the inside with a core originally of wood wool, which is a board no longer available made from a mix of wood strands and cement, is fixed within the post and beam timber frame using dry fixing methods such as bolts and screws. The building is laid out on a modular grid based on the stock sizes of the materials to avoid cutting and waste. The grid is a so- called tartan grid with a zone of 50mm which accommodates the thickness of the infill panels and the structure separated by a spacing of 600mm which is the width of commonly available panel materials.

The external and internal walls are not load- bearing which means that one can place openings in any position in the external walls and can position partitions anywhere you like on the different floors of the building. Importantly it also means that you can change your mind as you go along. You can stand in the part completed building and see which way has the view and which direction the sun is coming from and adapt the layout to suit. This can be very useful for self-builders who often find visualizing the inside and outside of buildings difficult from plan, section and elevation views. Self-builders have also found the idea of the grid a useful way of visualizing spaces and the size of rooms. The opportunity to fix the position and size of openings relatively late in the building process is not an opportunity you have with other forms of construction which tend to be fixed once the walls start going up. The separation of frame and infill means that the houses can be relatively easily adapted and extended to changing needs and expectations in the future.

Durability

This section suggests simple approaches to increasing the durability of dwellings which can reduce the use of resources in the long term. It also deals with reducing maintenance which can be a significant cost and a substantial nuisance.

The need for durability

Along with adaptability, durability is another aspect of building houses with a long useful life. Houses are commonly designed to last 60 years, and major refurbishments are often designed to last 30 years. In practice most houses have to last much longer than this. At current rates of construction and replacement, a house built in Britain today will have to last longer than the pyramids!

Fortunately it is relatively easy to design houses to last much longer. Designing buildings so that parts which have worn out or become obsolescent can be changed easily is described under ‘Adaptability’ above. What has to complement this approach is the use of durable products and materials and detailing for durability. These measures can reduce the use of resources and energy needed to provide and maintain houses over their lifetime.

It is also useful to specify materials which are self-finished – which do not require applied finishes which require maintenance. Examples are durable timber used in its natural state without an applied finish, and self-coloured render.

Good maintenance is a very important part of reducing the use of resources, and is a necessary complement to adequate specification of materials and designing details for durability. Make sure that there is adequate access, and pay particular attention to services by providing plenty of access ducts and access above glazed areas such as a conservatory or lean-to roof.

Durable materials and details

Tough, weatherproof materials should be used in exposed locations on the exterior of the building. Vulnerable details should be avoided, such as exposed parapets at roof level. Details should be designed to protect the building, such as designing deep roof overhangs and setting windows back in the openings away from the face of the wall.

The durability of products and materials should be balanced against their environmental impacts. Some inherently durable materials require significant amounts of energy to produce. Life Cycle Analysis is one tool for assessing this balance, and forms the basis of the Green Guide for Housing Specification. The green guide also gives guidance on replacement intervals and initial cost.

Costs and benefits

Durable buildings will consume less resources in the longer term, but may cost more in the first instance.

Summary: creating a durable home

The use of durable materials and details which tend to protect the building are relatively simple to implement and can extend the useful life of buildings. Durable specification and detailing has to be complemented by designing for adaptability and by good maintenance. The use of durable materials should be balanced against their environmental impact.

  • Avoid vulnerable details such as exposed roof parapets.
  • Design to reduce exposure, with deep roof overhangs and windows set deep within the thickness of the wall, for example.
  • Specify durable materials.

Avoid using materials which are dependent on regular maintenance for their longevity – conventional painted windows for example.

Accessibility

This section outlines the advantages of Lifetime Homes standards, which seek to improve accessibility for people with limited mobility above the minimum mandatory Building Regulations standards.

The Benefits of Lifetime Homes

Lifetime Homes (see pages 146-7) offer accessibility and design features that make the home flexible enough to meet whatever comes along in life: a teenager with a broken leg, a family member with serious illness, or parents carrying in heavy shopping and dealing with a pushchair. Lifetime Homes have sixteen design features that ensure a new house or flat will meet the needs of most households. The Lifetime Homes concept, which was developed on the continent some time ago, has been adopted as standard by a number of local authorities and housing associations. It will tend to make homes have a long useful life, and thus reduce the use of resources.

Part M of the Building Regulations covers accessibility, and Lifetime Homes features add to this the built-in flexibility that makes homes easy to adapt as people’s lives change.

Costs and benefits

Lifetime Homes standards offer greater accessibility and convenience for all residents including disabled people, old people, people with young children and people with short-term problems such as a broken leg.

The additional cost of Lifetime Homes Standards is marginal, with the exception of the requirement to provide space and service connections for a shower on the ground floor. The extra space required is not significant in the case of larger dwellings with a ground-floor WC. The potential extra cost is providing a ground-floor WC and space for a shower in a two-bedroom house, although a ground-floor WC could now be considered to be normal.

Summary: creating a convenient home

Consider incorporating the 16 design features of Lifetime Homes relating to the inside and external access to the dwelling.

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