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.
Bouncy floors can be a problem in older houses. Over the lifetime of a building, the services such as plumbing and electrics can be replaced a number of times. If the positioning of notches and holes is not controlled then you can end up with quite bouncy floors, as was the case with this one.
These notches (top and bottom of the joist) were at the mid span. This had significantly reduced the load capacity and led to all the furniture wobbling when you walked through the room.
Extensive alterations are being carried out to this bungalow in Stroud by removing the original roof and forming a new roof that will allow additional rooms. Due to the configuration of stairs and windows, there was no room for standard attic trusses so all of the new trusses are formed on site with timber and plywood glued and screwed together.
New house up to first floor level and waiting for the roof to go on.
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