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Advantages of Timber frame buildings

One thing that most construction professionals agree on is that if a prefabricated timber frame is used the time that it takes to construct a house on site can quicker than a traditionally built house of standard brick and block construction. This is because the timber frame is usually erected on site by the supplier’s own carpenters, in a matter of days rather than weeks. Seven to ten days is a typical time from the arrival of the specialist construction team on site to the frame being up.

Speed

One thing that most construction professionals agree on is that if a prefabricated timber frame is used the time that it takes to construct a house on site can quicker than a traditionally built house of standard brick and block construction. This is because the timber frame is usually erected on site by the supplier’s own carpenters, in a matter of days rather than weeks. Seven to ten days is a typical time from the arrival of the specialist construction team on site to the frame being up.

Many of the trades involved in the construction of a house, such as electricians and plasterers cannot work in exposed weather conditions and therefore cannot start until the interior is protected from the weather. These trades can start much earlier in the build programme of a timber frame house, which means that the building can be finished earlier. If a brickwork outer skin is required, this is built up after the frame is watertight, at the same time as the internal areas are being fitted out. Houses with all-masonry walls require a longer period for mortar and plaster on the inside to dry out and this can extend the build time by several weeks.

Quality and & Ease of Construction

The easiest part on site is getting the frame up, but the quality that results from the protected and controlled conditions of a factory must be followed through. This is why virtually all suppliers of kits also erect the frame. Because the frame is constructed very accurately it will be erected quickly and easily, but a high level of site supervision is required to ensure that the exacting standard of construction necessary is achieved.

Thermal performance

A clear advantage for timber frame construction is that the insulation is contained within the depth of the structure, so a typical timber wall can be thinner than its masonry equivalent, for example, by 50mm.

Once a good level of insulation is achieved, the amount of heat lost as a result of air leaking out of the building then becomes more significant. Timber frame structures tend to perform well on this score, because they are sealed to prevent moist air reaching the inside of the construction.

Risk of Condensation

Condensation is caused by warm moist air produced by space heating and activities such as washing and cooking cools. Moist air has a tendency to move to where the air is drier, usually from the inside to the outside. As moisture passes through the walls the temperature of the air drops, its capacity to hold vapour reduces and eventually water begins to condense. In winter this point may occur either on the surface of the walls, windows or other internal surfaces, or inside the construction, in which case there can be a risk of long-term damage.

A masonry construction, such as a cavity wall, can suffer from condensation at the point where the warm, inside air has passed through most of the insulation. It can do limited harm here, because modern insulation cannot rot. The outer brickwork leaf allows moisture to gradually pass through it and the inner face of the outer leaf is designed to allow water to run down it and drain away. However, condensation within a timber frame-wall cannot be treated so casually, and preventing it is a major concern for designers and builders.

The most effective method is to position a vapour check such as polythene sheet between the lining of the inside wall and the insulation, which will not allow any vapour to pass through it. Foil-backed plasterboard is often used for this role.

Rot and Beetles

It is very rare for a modern timber frame to suffer from rot. External timber elements, such as cladding and fascia boards are prone to rot if not well maintained, but the actual frame itself is well-protected. Wet rot is the commonest form of fungal attack although the other form, dry rot, is the one that provokes the most fear and excitement. In order for either of these to survive there must be a very high moisture content to the timber, usually at least 20%. In a modern heated house the moisture content will usually settle down at about 12%. Denied its principle requirements of warmth and dampness, rot will never be able to establish itself.

Infestation of the frame by insects is similarly unlikely. Many of the potentially damaging species only affect hardwood, or newly-felled timber. Provided the moisture content of the timber is below 20%, a timber frame will not be attacked. The ubiquitous woodworm or furniture beetle can infest drier timber, but is deterred by the well-ventilated, warm dry timber found in modern timber construction. A well-built and maintained timber frame will never produce conditions that are suitable for fungi or beetles.

Fire

Quite obviously, timber can burn, whilst some of the alternative materials such as masonry and steel do not, although they will eventually crumble and disintegrate if subjected to sustained high temperatures. However, there is some evidence to suggest that if the frame is not built correctly, it is more difficult to extinguish the fire and more damage to the structure can occur. Also it seems that timber frame houses are more vulnerable to fire damage during construction, before all the fire protection has been built over the frame. As far as the risks to people are concerned the crucial factor in survival is how quickly people can escape. If anyone is trapped, how long the construction of the house will protect them from flames and smoke until they can be rescued becomes important.

If asked whether a steel beam or a timber beam is most vulnerable when exposed to flames most people will say timber. This is a natural response, because steel doesn’t burn. In fact the answer is again not so straightforward. When steel reaches a critical temperature, it will fail, suddenly and catastrophically, because in great heat it softens and eventually melts. When a timber beam is place in a fire, the outside starts to burn immediately, as you would expect. But after the outer parts of the beam have been burnt, they turn into charcoal, which does not burn and actually insulates against heat. Because of this charring effect, the centre of the beam is protected from damage for a long time before the beam actually fails and collapses.

Provided that it has been designed and built by people who understand the technology, the risks from fire in a typical timber frame house do not seem to be any different from those that are faced by the occupants of a brick and block equivalent.

Structure And Robustness

Timber has proved to be a strong and durable material. If built well timber frames buildings will last for hundreds of years.

The exercise of building in timber requires more precision and planning than a brick and block property. For economy, the elements of a timber frame are carefully designed and calculated to use as little material as possible for the strength required. As a result, it is not straightforward to alter or extend the frame of an existing house and demolition of walls should not be undertaken without seeking structural advice.

If anything substantial is to be fixed to a timber stud wall, such as a heavy bookshelf, the fixings must be made into the frame, not the plasterboard wall covering alone which will not be able to support the load.

Green Construction

Timber has many environmental benefits not found in other building materials. The level of carbon dioxide (CO2) in the air is increasing significantly as a direct result of our lifestyle and mankind’s industrial activities and is a major cause of the greenhouse effect which in turn leads directly to global warming. Trees will lock away CO2 in their wood, which is retained throughout the existence of the timber. The use of timber as a building material encourages the growth and expansion of the forests that provide the supply, which absorb CO2 and therefore help to reduce the level of global warming.

Apart from the ability of trees to absorb and store CO2 itself, they also need less CO2-producing activities, such as industrial processes, to be created. To make steel for example, raw materials have to be mined, transported and then combined together in factories also producing waste. By contrast, there is almost no waste in timber production – even sawdust is used for chipboard or paper production.


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