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Douglas Fir Cladding

Working with Douglas Fir

Main Uses - Cladding, brise soleil, decking and joinery such as louvre screens.

Density - 480-580kg per m3 when at 13-19% moisture content.

Durability - Heartwood is moderately durable.

Movement - Low, meaning it is less prone to warping, twisting or checking, similar to WRC.

Wood Type - Softwood

Texture - Medium to coarse.

Grain Direction - Mixed, flat and vertical due to the small size of the log

Douglas Fir typically machines well but has a moderate blunting effect on cutters. It will also accept stains, glues, and finishes well.

Large Sections

Large sections are available up to either 2x6 or 4x4.

Douglas Fir beams are said to be less likely to check than WRC beams of the same size due to its higher density and lower rates of shrinkage.

Although these sections can be achieved, issues do occur as the timber dries out. Splitting and cracks are common natural characteristics in larger beams.

Douglas Fir Tree and Timber

Named after Scottish botanist David Douglas (though the scientific name is in honor of Archibald Menzies, who first described the tree in the 1790s).

Douglas-Fir is technically not a true Fir (Abies genus). It is its own species most closely related to Hemlocks. It is also commonly referred to as “Larch” in the Western US.

The scientific name is Pseudotsuga menziesii.

Distributiuon

Typically, Douglas fir trees are found on costal Western Canada. However, HiLine Douglas Fir is found more internal rather than the costal region. This means that the trees are grown in higher, colder climates leading to slower growth and smaller trees.

The slower grown trees mean more density and stability than its costal counterpart.

Due to the small nature of the tree, the knots are frequent but a lot smaller and sounder than the costal brother.

Although mature Douglas Fir trees can reach heights exceeding 75m tall and diameters over 2m wide, HiLine Douglas Fir are a lot smaller, only growing to 30m tall with diameters up to 0.5m wide.

Wastage

As with any timber, whether it’s cladding, flooring, a feature decorative component or standard batten, a wastage factor should be allowed. This is due to timber being a natural product and not every piece will be useable.

With Douglas Fir, 10% minimum is recommended. Ensure that as a minimum, a board’s finish width is accounted for on each end to allow for end trimming.

Environmental

PEFC Certified - PEFC/16-37-77

This wood species is not listed in the CITES Appendices and is reported by the IUCN as being a species of least concern.

Colour

Usually a light brown colour with a hint of red and/or yellow. The sapwood is lighter in colour than the heartwood which is yellowish brown.

Fixing the Timber

With this species, stainless steel fixings must be used. For projects within 15 miles of the coast, marine grade fixings must be used at 450-600mm centres. We advise all claddings are installed with expansion gaps, and as with all hardwoods, we advise pre-drilling. This helps to reduce potential splitting.

Please ensure relevant supports, at correct centres, are used with HiLine Douglas Fir Cladding or Brise Soleil. Lack of supports can lead to sag, bow, creep and twisting.

For vertical applications, we advise chamfered top and bottom edges to be cut to allow water run-off. Should water sit on any square cuts, it will absorb into the section and likely cause swelling.

For all cut and exposed ends, we strongly advise using an end sealant. This can be found in the accessories list on our quotation. Sealing the end-grain slows down moisture loss and lets the board dry more evenly, helping reduce the amount of end splitting that can occur.

Any claims made to VT which are caused from insufficient supports or poor installations will not be accepted.

Fire Treatment

Douglas Fir has successfully passed the European Class B’ and C’ FRX testing.

For external applications, we do not advise brush / spray applied Fire Treatments due to weathering, but these are fine for internal applications.

Timber Lengths

Although timber lengths vary from 3-4.8m (heavy 4m), we do allow a small % of cut back with any parcel. Please check stock lengths with us before ordering.

Ensure that as a minimum, a boards finish width is allowed for on each end for site trimming following end/ drying checks.

Detail Drawings

Factory Staining

Gallery