Structural softwood generally comes in two grades in the UK – C16 and C24. The C means coniferous and the number represents the strength class that the timber has reached – the higher the number the stronger and stiffer the timber.
For roofs, generally Grade C16 will be sufficient as the size of timbers is often determined by the insulation requirements. Recent changes to Building Regulations have meant that the insulation thicknesses have increased and therefore size of timber needs to increase as well.
For upper floors, there is not the requirement for as much insulation and the size and grade of timber is more determined by the loading and span of the joist. Generally, as small a joist as possible to meet the requirements so you lose less internal space, i.e greater floor to ceiling heights.
C16 grade timbers will normally be less expensive than the same size in grade C24, as they have more defects,i.e knots, grain deviation and wane but if they work for their intended use, thats the important bit. Grade C16 timber is also more likely to have been grown within th UK, as the climate is good for faster growing varieties of trees so less carbon footprint from transportation costs from overseas. Grade C24 comes from slower growing areas such as Scandinavia or the Alps. If your timber will be seen in the final design, then you may want C24 as it will have fewer defects and be of a more uniform condition.
There is no need to automatically go for C24, as it could be more expensive without any additional benefits.
We work on oak framed garden room extensions with Timberpride, Tetbury. In addition to the extension, a large opening was formed in the existing rear wall. Below are some of the in progress photographs with final images here – Oak Frame Extension.
We worked on this project with Austin Design Works a few years ago. It was previously a house and separate garage but now fully upgraded and with a contemporary link. The building makes the most of the views across the valley towards Inchbrook. There are a few in progress photographs below but follow this link to see the final design – Cotswold Stone Family Home.
We have invested in some new software to analyse and design complex connections and member shapes using IdeaStatiCa Connection. We have been using it to check some cantilever members of a canopy with the lower plate in compression with potential buckling. It has the potential to check any shape of connection.
There are many different types of surveys and investigations for buildings and the Construction Industry Council (CIC) has produced a useful document defining the different types. The term “structural survey” although widely used should be avoided as it is not well defined and can lead to confusion as to what is included or excluded. A link to the document is included below.
Contemporary Alterations and Extension in Wotton under Edge
We have been working on this contemporary make over of this house in Wotton under Edge. It has been a complete transformation of a house with extensions on three sides. There was a substantial part of the original rear wall removed to create a light filled room.
Designer: Oasys Property Solutions
Contractor: JAS Building Services
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