Alternative Building

General

It is taken as “Normal” that all buildings, today, are built of brick, timber frame with infill or steel / concrete frame with infill.

However, various other techniques are equally valid, and are found throughout the UK, where some are now being revived because of their sustainable and energy sensitive construction methods and credentials.

Just a few of the possible “Alternate” techniques that could potentially be profitably employed in the domestic construction scene (and possibly others) are:-

  1. Cob
  2. Straw Bales and Compressed Straw
  3. Rammed Earth
  4. the use Sprayed Waste Paper and other natural insulations
  5. the use of cellars
  6. the use of “Off-site” produced “pre-fab” sections and structures.

There are several others that could also be added to the list.

Cob

Traditional Cob construction, as seen in many old farmhouses, barns and other rural village buildings throughout the UK, Europe and, indeed, the world using similar techniques, used farm derived clays mixed with straw and cow manure which was trodden together by the cows in the yard until a uniform mix was obtained.

As can be imagined, this mixture, when placed as a wall, tended to be little ripe smelling and somewhat bug-ridden until it had dried out and had been coated with a lime render and colour-washed.

Today's mixture still uses locally derived clay and vermin resistant straw (usually rape-seed or barley), but the cow manure and cow treading elements are left out.

“Given good boots and a sound hat, a cob wall will outlast most of its builders” is an old saying resurrected by a leading modern exponents of the art of cob.

In other words, provided that sound, solid and waterproof foundations are in place, together with a sound, solid and watertight wall cap on top of the finished structure, a cob walled structure will last for many years. This is evidenced, of course, by the fact that many traditional cob structures, some of which are several hundred years old, are still actively in use today, having been modified, undergone several transformations and updates throughout those intervening years.

Cob should be built, preferably on a stone foundation that should protrude above the finished surrounding ground level by at least 300mm, preferably 450 - 600mm, and should be of a width at least 100mm narrower than the finished cob wall that it supports.

Cob should be roofed over with weather-tight material that protrudes by at least 600mm, and preferably 900mm, the outside face of the wall.

Cob should be allowed to dry thoroughly and naturally, which may well take several months, even as much as a year, dependant upon location and exposure, after which it should be coated with a traditional lime based mortar render and a white or colour wash.

Building in cob has several environmental features, firstly with the considerably reduced embedded energy expended in its structure as the materials are totally worked on site (very little manufacturing energy to be built in and a much reduced transport energy content), secondly it is self insulating, can be shaped as required on site as it is built, and has considerable inherent compressive strength even though its pull-out strength is limited - even weak.

Whilst the build time for the base structure and cob is relatively quick, the final completion time, however, can be protracted to allow for complete drying out. It will be very noticeable, however, that there are no drying or settlement cracks when the whole process is complete.

Straw Bales and Compressed Straw Panels

The use of Straw Bales may sound, at first hearing, as though this author is living in fairy-tale land, with The Three Little Pigs and The Big Bad Wolf, however the idea is not only a sound one, it is valid and well proved into the bargain.

Using the correct type of straw - which has to be vermin and mildew resistant and waterproof, in the right sized bales, can enable considerably large volumes to be constructed in a very short period of time and it is self-insulating.

As with cob, this technique requires sound foundations and cap and should be coated with a material such as a traditional lime mortar render.

Also, as with cob, there are specific techniques required to construct such walls and these have to be applied correctly for the method to be successful. (Refer to the “Amazon Nails” website)

Cob and straw structures may sound like a backward step in today's modern world, but there are structures made of cob still standing in the UK that are over 400 years old and straw bale buildings, correctly based and roofed have been standing and in continuous use now for some tens of years.

Straw, correctly compressed and bonded with eco-friendly resins has been in use for many years as a very strong wall panelling and flooring material. It can also be used as an insulant material as well and should behave well when used as the insulant substrate with under-floor heating systems.

Rammed Earth Construction

“Rammed Earth” construction could almost be considered to be a modern-day, almost industrialised, version of cob.

It does vary, however, in subtle ways. The process is more akin to building in un-fired brick clay and uses very modern industrial type engineering techniques instead of the traditional hand methodologies employed in cob construction.

As with cob and straw bale, similar foundations are required and appropriate protective coatings are needed.

The technique includes using non-stick smooth sided steel shuttering fixed in a similar fashion to those used when casting slip-form concrete.

Because of the required structural thickness of the walls built using this technique, they are very strong in a compressive manner and are self insulating. They do not, however, similar to cob and straw bale, exhibit high pull-out strengths.

Sprayed Waste Paper and other natural insulation materials.

A very useful and relatively cheap method of providing high levels of insulation to both horizontal and vertical surfaces is to pump into adjacent voids, pulped and treated waste paper.

This insulation material is both an efficient and user-friendly material which can be very quickly and effectively applied to almost any structure type. (dust masks and goggles should be used during the spaying process as part of the normal operative PPE)

Treatments can include mildew fungicide, vermin proofing, water repellent and fire retardant.

This material can be laid between joists and in wall cavities providing suitable precautions are taken to ensure its long-term stability.

It does not, however, exhibit great compressive strength in its raw shredded form, but with suitable eco-resins, as with strawboard, can be formed into panels and sheets.

Another natural material that is becoming more widely used is lambswool in the form of batts or rolls. This is treated prior to use to inhibit smell and natural oil leaching. It is however relatively expensive to purchase compared with other formed materials, but should be no more expensive to install.

Cellars / Basements

Cellars or basements do not appear to be a normal option for construction in the UK these days, even though they were the norm for many levels of housing and commercial premises in the 18th & 19th centuries.

They are still very much in use throughout Europe, the US, Canada, Australia and most other parts of the world, where water tables allow, and should be considered for revival here in the UK, especially on tight sites.

They provide self-insulated accommodation, even if this is only used to house boiler plant and laundry appliances.

Obviously, this space can also house, other accommodation such as bedrooms and studies so reducing the heat requiring footprint above ground. However for “living” accommodation, ventilation is certainly a requirement and daylight introduction through the use of light tubes and / or lightwells is also a desired requirement.

“Off-site” Build

“Off-site” building is where the majority of a structure's construction, or of specific elements of that construction, is fabricated within a closely environmentally-controlled factory environment.

Very close tolerances can be achieved with very little construction waste and with the very much improved building tolerances comes reduced construction energy consumption into the bargain.

All of the materials used can similarly, be closer controlled for both quality and finish as well as keeping to tight project deadlines and margins.

Almost any particular section of a building from a kitchen and bathroom to a fully fitted lounge and bedroom can be manufactured off-site and shipped onto a pre-prepared site base for cladding and final finishing, which can also be off-site prepared.

Today, the entire building including it's general finishing and full servicing can be built off-site and shipped in.

Environmentally, this can save in terms of materials handling both to site and on site as well as obvious site wastage. This technique when correctly planned and employed reduces time scales on site and has obvious consequential financial savings which emanate from all such physical action savings. In addition to the site-use energy reduction, the embodied energy in the actual build is also greatly reduced by a very much more efficient use of materials and labour.

With acknowledgement for use of images to: