Of course, a loft conversion is the best way to add space, but your choice of wood matters. Builders require a strong, straight and internal structural grade timber. If you are costing materials out, here is the typical order for a loft conversion.
Structural timber: C24 (often preferred)
Builders often call for graded structural timber when they need to use material in joists or rafters. The C24 is stronger and more rigid than the C16, so it will get mentioned most of the time.
Common uses include:
Floor new joists (if there is a room above)
Strengthening existing joists (where required)
Openings for stair trimmers and noggins.
Whilst C24 is not required on every job, many builders specify it to avoid springiness and other performance issues. For a Timber Merchants Portsmouth, visit https://www.timbco.co.uk Covering Portsmouth
Studwork and framing timber
For internal walls, dormer framing and boxing in, builders generally order CLS (Canadian Lumber Standard) or similar timber frames.
It is popular because it is:
No nonsense, reliable and straightforward
Most often dry kilned (less movement once installed)
Perfect for tsud walls and partitions.
Sheets: Flooring and sheet-based boards
A lot of sheet material goes into loft conversions. Typical orders include:
New Floor: Tongue-in-groove chipboard flooring (Often moisture resistant)
OSB3 (for example, for dormer cheeks)
Marine plywood for increased strength and fixing area.
Of course, the right thickness all depends on spans and design, so builders often look to their engineer for the specifics.
Roof battens and (if needed) treated timber
For example, if the covering of a roof is being changed, then builders may order roof battens and occasionally treated timber for any areas which will be exposed to moisture over the duration of construction.
The majority of any loft timbers are internal, but care is still vital if materials are left on site.
Small But Needed Items:
Noggins and packers
Firring strips
Softwood door linings and architraves
Exterior-rated fixings if needed.
A practical takeaway
The majority of loft conversions will contain a combination of C24 structural timber, CLS for studwork and chipboard/OSB/plywood used in flooring and sheathing. Sizes and quantities should always match the engineer’s drawings exactly.