There are many materials to choose from when planning a conservatory. The first thought for most people is hardwood; however, there are occasions when alternative materials can be considered.
Most architects and professional designers will agree timber is the most suitable material for constructing beautiful conservatories. Timber offers flexibility in design that no other product can. Inspirational designs and ingenious concepts can be created in timber much more readily than any other material.
Hardwoods, particularly the tropical hardwoods like Sapele, Meranti/Luan and Iroko are some of the more commonly used. These timbers are preferred by joiners because they are easy to work with and the end product is very reliable. The hardwoods will keep their stain or paint finish for 2-4 years -depending on the location (South facing conservatories and conservatories near the coast will need painting/staining more frequently than conservatories facing North, or in the shade)
Hardwoods are not necessarily ‘harder’ as the name would suggest (Balsa is also a Hardwood) but they tend to have tighter fibres which gives the wood a stronger and more stable structure that limits the expansion and contraction – which results in improved resistance to moisture.
The serious issue with all tropical hardwoods is sustainability. Some hardwoods are grown in sustainable managed forests but some are not. Europe purchases an enormous amount of timber, and merchants buy timber from many sources in order to fulfil demand. The ‘Chain of Custody’ from the forest to the merchant for much of this timber is difficult to prove, as recognised by ‘The House of Commons Environmental Audit Committee’ report in 2006 which concluded:
Illegal timber is currently a fact of life within the UK timber trade. It is therefore virtually impossible for even those companies that are attempting to eliminate illegal timber from their chain of supply to guarantee that they have done so
The timber industry, importers, merchants and federations are all working together with the government to drive the UK’ timber industry toward total sustainability, and conservatory companies certainly have a responsible role to play.
Softwoods are generally more sustainable as most come from the EU. They are commonly used by developers and builders for the windows and doors in new developments and are a cheaper alternative to hardwood, but not generally recommended for the construction of conservatories.
Softwood tends to move more than hardwood, and whilst this is restricted by the brickwork surrounds of windows in houses, the same does not apply on most conservatory designs – the conservatory tends to be a structure which is primarily self supporting.
Softwoods tend to have a looser fibre structure than the hardwoods which makes them more likely to expand and contract. This causes the racking and twisting of the wood which causes the paint/stain to wear off and moisture to enter – causing the wood to expand and contract further.
Another timber that should be mentioned is European Oak (hardwood) mostly grown and managed in sustainable forests in Eastern Europe. For the construction of conservatories, the Oak is seasoned – removing much of the moisture content in the wood – to produce a timber that is versatile and strong and can be painted, stained or oiled.
Another timber product that is available is engineered timber. This is made by gluing and laminating (this timber is also referred to as Glu-Lam) sections of softwood together so that the grains run in opposing directions, which helps restrict movement, Engineered timber is structurally very sound although its cost, like seasoned Oak, can be prohibitive.
Whilst timber is beautiful and on some projects – listed buildings for example – the only material that can be considered, there are occasions when alternative materials might offer some benefits that timber cannot.
Aluminium should be used in one way or another on all conservatory projects. Every timber conservatory should have a powder coated external aluminium capping bar which provides an almost completely maintenance free roof. However, Aluminium can also be the main structural material in its own right.
Some modern or contemporary projects where large open expanses of glass are a feature will often look better with the slim lines that aluminium can offer.
Aluminium frames require little maintenance and for this reason they are frequently proposed as the material of choice for conservatories on commercial buildings and conservatories that extend over 2 or more storeys, or conservatories on roofs (Observatories).
Aluminium is usually thermally broken (it has a rubber break in the centre) to prevent cold bridges – where the cold from the outside is conducted inside – making them warmer than just standard aluminium sections. However, aluminium does not have the thermal qualities of timber, but products are continually being developed so this may be the case, one day.
Un-plasticised Poly Vinyl Chloride / uPVC
For the self respecting conservatory connoisseur, uPVC is a material that rocks few boats. However, like it or not, there is a place for uPVC in the conservatory market. I do not think it is necessarily the material that people object to – more the industry that has embraced the material and created a monster of it!
uPVC has had a tough time, more to do with the unprofessionalism in some areas of the double glazing industry. The uPVC kit conservatory will never perform anywhere near the standards that you would want, due to frequently poor design work by inexperienced salesmen – who are concerned more with their commission than your interest. uPVC has also been associated with companies that build to the absolute minimum specifications to maximise quick profits before moving on to the next unsuspecting customer.
However, uPVC can be used to produce products that can complement many houses, and some of the window systems can also be adapted to the construction of conservatories. There are new systems evolving all the time – with the current advancement seemingly focussed on paint finishes that dramatically alter the feel of uPVC products – with some success.