Timber Engineering Europe
Traditional (softwood) Joists
Soft-wood joists are ideal for smaller builds where relatively short spans are involved.
Traditional timber floors are manufactured from a range of C 16 or C24 Grade Timbers.
Tradition joists sizes are:
38mm x 225mm KD. Graded/Treated Timber Joists
44mm x 195mm KD. Graded/Treated Timber Joists
44mm x 219mm KD. Graded/Treated Timber Joists
KD (Kiln Dried)
By drying timber to below 20% moisture content, the risk of shrinkage once the timbers
have been installed is greatly reduced which eliminates remedial work at a later date. Kiln
drying is a process dries the timbers in a uniform and regular way.
Timber must be graded (and dried) if used in internal structural applications as stipulated by
building regulations. Timber is graded to either C16 or C24 and this can be achieved in two
ways; 1. Engaging a tradesman who has qualified and is licenced to inspect the timbers and
award a grade, or a mechanical methods is used for the same purpose. Each individual piece
of timber is checked for Species, Knot Size and Type, Slope of Grain, Tightness of grain,
Compression Wood, Rot etc. On completion, they will then be stamped with a code that
displays this information. The grade C24 can only be achieved by imported timber. Home-
grown timber from UK sawmills will make C16 only and so will have reduced span and
possible loading capability.
Vac – Vac Treated Timbers
- Timbers are put into a treatment vessel.
- A vacuum removes all the air from the wood and the vessel.
- An osmose preserve is then flooded into the vessel.
- The vessel is then pressurized, forcing the fluid into the timber.
- The fluids are then removed and a final vacuum is applied removing all excess fluid
- The timbers are now preserved and protected from decay and wood-boring insects
By regularising the timber the end user can be sure that in whatever application each piece
will have consistent and "regular' size, avoiding the need to ‘pack’ as was common many
years ago when machining facilities were quite basic and a finished size could vary.
C16 and C24 are the main softwood strength classes used today.
A strength class is a group of species/strength grade combinations which have similar
strength and or mechanical properties. There are different C strength classes however C16
and C24 are the two most frequently used.
You may also find the grades SC3 and SC4 in some contexts but these are the old strength
classes that have been superseded by the European strength classes as described above.
SC3 is approximately equivalent to C16 and SC4 is approximately equivalent to C24.
This is a typical information stamp you will find on a graded joist, giving all the information
to the supplier, user and regulatory bodies concerned.