Content supplied by RICHMOND OAK CONSERVATORIES
Broadly speaking, the types of timber used in the construction of conservatories, orangeries, garden rooms and sunrooms, falls into two main types:
In simple terms, softwood is faster growing, more open grained and less durable for external use than most hardwoods that are denser, tighter grained and more durable.
Typical hardwoods used in conservatory construction are sapele, idigbo (both of which are described by the Friends of the Earth as vulnerable to extinction), iroko and oak.
Typical softwoods include douglas fir, Siberian larch and pine (usually described as European redwood, to disguise its true heritage).
Where is the Wood Sourced From?
Most softwoods come from Scandinavia or Eastern Europe and most hardwoods emanate from the Southern Hemisphere, South America, Africa and the Philippines. However, when it comes to oak, that which is used for construction tends to come from France, Poland and Eastern Europe.
The Popularity of Oak
Oak, in particular, is used widely in the timber glazed extension industry because of its natural beauty, strength and longevity. It is used primarily three different forms
- Green oak: this is a term used to describe unseasoned sawn timber with a typical moisture content of between 60-80%
- Air dried oak with a typical moisture content of 30-60%
- Fully seasoned oak will have a moisture content of less than 20%
Why Does Moisture Content Matter?
The more moisture content in the timber, the more it will move, twist and bow during the drying process. That is not good when located close to sealed glass units, which are prone to breaking down (misting up inside) when subject to movement in the frame into which it is glazed, or leaking when fixed to green or air-dried roof rafters.
There can also be significant splitting and movement in the joints which can cause air and water penetration.
Avoiding the Movement Problem
This movement can be avoided by using engineered or glulam construction methods. By using 20-30mm thick boards, glued together so that the grains alternate, you get a more stable timber beam which significantly reduces future movement. The glulam beams are much stronger and less likely to bow or deflect. For example, a 225mm glulam beam has a similar strength as a 300mm non-engineered beam, despite using 25% less timber (which means it can be a cost-effective solution).
What is the Cost Difference Between Soft and Hardwoods?
Whilst softwood typically starts off much lower in cost than hardwood, by the time you add the cost of labour, painting, handles, locks, hinges, glazing, packaging, and transport, the price difference reduces significantly.
Choosing the Right Wood
When investing in a timber glazed extension for your home, you should be considering the longevity of the structure and the value a well-designed wooden conservatory, orangery or garden room can provide.
A softwood structure might save 10-20% in the initial cost, but will probably require replacement within 15 years. On the other hand, a well-designed, professionally installed hardwood conservatory, looked after properly, could still be a significant feature in 25+ years.
The Importance of Certification
Many hardwood timbers are in danger of extinction by over harvesting of the rainforests so it’s very important to ensure the timber you propose to use has legitimate Forest Stewardship Council (FSC) Certification, meaning that the trees are being re-planted for future generations.