Tuesday 20 March 2007

CONCRETE OR WOOD?


I have noticed recently that there seems to be a bit of a battle going on between two different building methods. The tried and trusted method of erecting houses with concrete is being challenged by the new(?) idea of wooden framed structures. The most noticeable sign is the “Concrete built is better built” writing on the front of cement lorries. Houses are getting better all of the time, especially when you compare them to the prefabricated houses of the 1940’s. After World War two there was a desperate housing shortage. Homes had to be built and fast.


PREFABRICATED HOUSING
Prefabricated housing was documented as far back as the seventeen hundreds when homes were shipped over to America from England. More recently the idea was used in 1945. Prefabs were originally built as temporary "homes for heroes" to ease the housing shortage after the Second World War and were meant to last only ten years. The English Government's "Temporary Housing Programme" called for 500,000 homes, each to have two bedrooms, a bathroom, separate lavatory, kitchen with a fridge (because there was no pantry) and a living room. This sounds basic by today's standards, but 50 years ago a prefab provided a vast improvement in living standards for couples that had been waiting for years on a council housing list, living in rented rooms or squashed in with in-laws.

Because of a shortage of traditional building materials, the Ministry of Works allowed prefabs to be built from anything available. At least eight different designs were accepted, with names such as Arcon, Phoenix, Tarran, Uniseco and Universal. Some were built entirely of aluminium, but most used a form of corrugated asbestos-cement sheeting bolted to a steel and timber frame. Former aircraft factories turned to making walls and partitions, and obsolete joinery factories were re-opened for other parts. Each prefab was made up of about 2,000 components, which were assembled on site.

The prefabricated panels were a sandwich with a wood-wool filling between sheets of corrugated asbestos-cement. The houses took eight unskilled men eight days to assemble. It sounds crude, but the construction industry learnt a lot about innovation and planning. Each prefab should have cost about €800, the average was €1,800. Some historians have questioned whether the exercise was worthwhile, but at the time there was little alternative. There was no time to set up brick or concrete factories.

By the time the temporary homes programme ended in 1951, 156,000 prefabs had been built. They included innovative designs such as hot-air shafts that radiated heat from the open coke fire to other parts of the house. There was a big problem, however: at the time the homes were cold in winter and baking hot in summer, and condensation turned clothes green with mildew, much the same as living in a mobile caravan. There are a few prefabricated homes near the university in Derry that have been modified to today’s standards and look very attractive. Most prefabs were demolished in the 1960s and 1970s though like the pre-fabs on the shore front in Buncrana.



CONCRETE OR WOOD?
Both industries have selling points. The argument for concrete strengthens when the topic of large structures is mentioned. Bridges and large office buildings rely on re-enforced concrete to do the supporting, a job that wood would be pushed to do. Some projects in developing countries rely on lime free concrete to make their houses. This saves the trees being cut around them, which protects their ecology.

The concrete industry defends itself again with the claim that their product is recyclable. It can be crushed down to a smaller size, granted, but the energy used to do this would be phenomenal, especially if it was re-enforced with steel. The concrete industry manufactures on site and distribute to about a forty-mile radius, which keeps the fuel use down to a minimum after the mixing process.

The timber industry has to defend itself too. Because of Irelands lack of forestry there is a necessity to import a majority of the wood that is needed for the projects, using gallons of fuel in the process. Countries with wet and harsh climates, like Scotland, Scandinavia, and now Ireland, are increasingly choosing timberframe at the preferred method of building new homes and the manufacturers claim these points in their favour:

Speed of construction saves money on the build.
Accurate, straight walls keeps the draughts out.
No drying-out time move in quicker.
Environmentally friendly, erm.. Not entirely yet, until Ireland starts growing more wood!
Approximately 40% heat savings due to better insulation. Thankfully not asbestos any more! The best is wool or hemp.Flexibility for future alterations you can extend at your leisure without messy concrete walls to get rid of.
BIG IS BEST ?
The last point mentioned above is one of the burning issues in house building….. making houses bigger. The amount of energy that goes into a house is nothing compared to the energy that is used to light and heat it over its lifetime. With the passion now for houses to be built as large as possible for the money available, which could mean the house uses far more energy than a more modest building. The emphasis needs be put on insulation and energy saving as well on initial building costs. Timber frame companies are doing well as they use environmental information as a very effective marketing tool. Concrete companies as yet seem to have the last word as timber frame houses are usually externally reinforced with concrete blocks. Expect the battle to continue!

Environmental.

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