How long do oak framed buildings last? If constructed and maintained properly an oak framed structure can last in excess of two hundred years. There are many historic oak framed buildings in Britain and all over Europe even older than this. Anyone who has witnessed a fully grown mature oak tree will agree it is a magnificent sight. Without the natural strength of the wood itself they could never grow to such a prodigious size. They would collapse under their own weight long before maturity. Early builders recognised this and oak became a favoured building material. Along with the sheer size and quantity of timber obtained from one tree, it was perfect for even the largest structures.
Timber framed houses and outbuildings have seen a huge surge in popularity in the last few decades. This is largely due to the widespread availability of oak framed building kits which allow fast and simple construction. Most contemporary oak framed houses are less than forty years old, so judging their longevity is potentially difficult beyond this point. However, oak frame construction details are largely unchanged from hundreds of years ago. As a result, the lifespan of modern timber framed houses can be judged from existing historical examples.
Sources of Damage to Oak Framed Buildings
Oak, especially when aged and seasoned, is extremely resistant to the elements. There are other factors that can cause damage and shorten the lifespan of the structure.
Oak, being wood, is obviously susceptible to fire and will burn. It does however have an extremely slow and consistent burn rate. Also, as the outer layer burns it turns into charcoal which then forms an insulating layer. This protects the interior from further combustion and weakening. If caught in time, the damage will be far less substantial than with other types of timber. While steel frames do not burn, at high temperature they will soften and melt. This can lead to a sudden and catastrophic collapse that will not happen with oak frames.
The natural water resistance of oak is well known. If it is contact with high levels of moisture for sustained periods it can still be affected. Bathrooms and kitchens, which will naturally produce moisture should be adequately ventilated. This will prevent condensation that can lead to water absorption and rot. In outbuildings, it should be ensured that any points of contact between the frame and ground are properly waterproofed. This will prevent standing water on the ground surface damaging the base of the frame. In particularly damp environments, it may be worth using air dried oak for its superior water resistance.
As oak is highly resistant to insect infestation, fungal infections are the greatest threat. If the moisture content of the wood rises above 20%, it can become susceptible to dry rot or cellar fungus. These can weaken the timber to the point where replacement is the only solution. Even if dried out, the timber can be softened enough to allow pests such as Death Watch Beetle to burrow in. these will then feed on the softened wood, weakening it further.
Construction Oversights That Can Damage Oak Frames
Different styles of oak framed buildings each have their own potential weak points than can affect structural integrity. There is a common misconception that the natural shrinkage of green oak will weaken the structure over time. Any oak framed kit from a reputable company will have been designed to take this into consideration. In fact, as the green oak frame contracts, it will tighten around the seasoned pegs at the joints. As the pegs do not shrink, this forms an extremely strong joint that will not move.
This traditional design now uses modern insulation panels to fill the gaps between the frame. Although these are more flexible than traditional materials, as the frame shrinks, gaps can appear. This will not weaken the frame itself but can allow water to penetrate and cause damage.
As noted above any points of contact with the floor should be designed to prevent standing water affecting the timber. Often this is as simple as using steel base plates as a barrier between support posts and the floor. Any outbuildings that are open to the elements should not have areas where water can pool in contact with the frame.
When extending timber framed houses, contact points between the extension and original structure must be properly waterproofed. If the extension is glazed or part brick this should also be a priority. If not, the resulting rot could spread from the extension to the main framework.
Timber Framed House Mortgage Problems
Until fairly recently, acquiring a mortgage for a timber framed house could be difficult. Many timber frames used for construction were only guaranteed for a maximum of sixty years. Due to brick and stone being the standard materials for the majority of construction, they were seen as ‘non – standard’. This made lenders reluctant to offer mortgages as the properties were seen as a risk in the case of repossession. If a borrower defaults on repayments, the lender will repossess the property. and sell it to recoup their losses. If this resale seems unlikely, the mortgage is seen as too high a risk to the lender.
Although more lenders are now willing to offer mortgages for timber framed houses, some are still resistant. If the property is less than ten years old, they may ask for a National House Building Certificate to endorse it. If the house has a brick or stone outer layer over the frame it is more likely a mortgage will be approved. As many timber framed houses are still classed as ‘non – standard’, it is worth consulting a mortgage advisor if you are in any doubt.
Hardwoods group are specialists in the construction of quality oak framed buildings. We have a range of kits designed for longevity and ease of construction. We also offer a bespoke design service to make your unique design a reality. Contact us today to discuss your requirements, we will be happy to help.
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