Green oak is defined as oak that has been freshly cut and is ready for use in construction. However, oak roof trusses and other oak based frames is not a new craft; green oak in construction dates back many centuries and was a common material for carpenters who used it for barns, houses, and church roofs. Oak in roof construction is definitely not confined to the history books; it is very much a prominent material for feature trusses and roof framing today. Here we will look further into the reasons why oak is still used as often today as it ever was.
So, what exactly are the major differences between working with green oak and modern timber for construction and roofing? Today, timber used for construction is seasoned by kiln or air-drying, which completely dissipates movements that occur as the timber loses its moisture over time. But why can we not do the same for oak? There are four major issues with using seasoned oak for framing work, which relates to the attributes of the oak itself:
- Hardness – Seasoned oak is considerably tougher to cut and shape than green oak or timber, even when using power tools.
- Drying Time – Oak dries rather slowly and typically will take six to eight years to air-dry and lose any excess moisture. Even the modern technology of today cannot reduce the drying time for oak of certain thicknesses. Due to the fact that oak roofing frames are designed individually, there is no stock of oak ready for demand so any roofing project is on hold for that period of time.
- Movements – Oak has a tendency to shrink during the drying process, which would require the seasoned wood to be cut again to fit the requirements.
- Fissures – As well as movement during the drying process, oak runs the risk of creating fissures. These cracks and openings create difficulty when cutting the wood and make edge moulding particularly difficult.
For more information on how oak is used within roofing construction, do not hesitate to get in touch with us. Our team will be more than happy to discuss any plans or designs for feature trusses with you.