Timber

They are used in construction and carpentry for formwork, temporary supports, frames, finishes and site works. Fir is light, easy to work and inexpensive, suitable for temporary structures or indoor uses. For load-bearing and permanent works the sizing must be verified by a technician.

Rough-sawn timber has an unworked surface and actual dimensions that are often larger than the nominal size, while planed timber is machine-finished and has a smooth surface and precise dimensions. Rough-sawn timber is suitable for carpentry, formwork and temporary works, while planed timber is for finishes, cladding and visible frames. Choose based on the end use and the type of work you will carry out.

The cross-section, that is the thickness by the width of the scantling, is chosen based on the load and the span between the supports, and is given in centimetres on product sheets. Larger scantlings are stiffer and span greater distances, while smaller ones are used for frames and light structures. For significant loads, ask a technician for the calculation rather than choosing the section by guesswork.

Single-layer or three-layer fir laminated panels are used for internal walls, shelves, furniture, worktops and some cladding. The thickness must be chosen based on the span between the supports and the load they must bear. For floors or slabs specific checks are needed, because behaviour depends on how the panel is fixed and on the load.

Untreated fir absorbs water and can warp or rot, so it must be stored raised off the ground and covered with a sheet that allows air to circulate. At points of contact with masonry or ground it is advisable to use a protective treatment suited to this type of wood. For works permanently exposed outdoors, consider timber treated in an autoclave.

Wood knot patches are used to close knots, holes and surface defects before painting or finishing the surface. They are inserted into the hole after the cavity has been prepared, and glued with an adhesive suitable for wood. Once dry, the plug must be trimmed and sanded to obtain an even surface to treat.

For temporary works such as formwork, props, scaffold platforms and protections, rough fir boards and scantlings are used, which cost less and are easy to replace. Scaffold boards must have thicknesses and characteristics suitable for the use, as indicated in the technical sheets. For raised working platforms the boards must be checked for load capacity and fixings.

For dry indoor uses fir does not necessarily require heavy treatments, but it should be protected with a clear finish or a wood paint if it is exposed to dirt and impacts. The finish must be chosen based on the use: for example, boards for kitchens or bathrooms have different requirements. Before applying the product, read the label to check its compatibility with the wood.