Wood Types

Scots Pine, European Redwood (Pinus Sylvestris)

  • Most commonly used in UK joinery construction
  • Heartwood is highly suitable for joinery manufacture with moderate to low movement characteristics and moderate durability when out of ground contact.
  • Sapwood should make up only a low proportion of the component volume for exterior joinery as it is low in dimensional stability and is non durable against exterior wood rotting fungi.  The sapwood can be treated with traditional vacuum impregnation methods if required and will absorb superficial preservative treatments.
  • The margins of live and dead knots contain extractives (tannins) that will stain light coloured paint finishes. This staining is dark brown or even purple in colour.
  • Resin will be contained in live knots and in certain early wood bands.  Liquid resin can diffuse through the surface coating. This often results in amber/brown stains on light coloured coatings.

Target moisture content of timber prior to machining should be between 12 and 16%

Siberian Larch (Larix deciduas)

  • Siberian Larch has a moderate durability.
  • While Siberian Larch has a higher density than softwoods such as Scots pine there is a tendency towards moisture related movement.
  • Naturally occurring resins and tannins that migrate to the surface can result in some issues with the drying of coatings. Low viscosity base coats can have difficulty absorbing into the dense surface of this timber.

Western Red cedar (Thuja plicata)

  • Very stable timber ideally suited to joinery manufacture and especially suited to the production of cladding.
  • This timber has low density making it ideal for cladding boards, but it does not resist physical damage and is quite brittle in thin sections.
  • High natural durability.
  • Opaque water-borne finishes can stain due to the very high water soluble extractive content, only specialist primers can stop extractives coming through paint finish.

Meranti

  • Meranti is a term used to describe a group of approximately 50 south east asian wood species.
  • Certain versions such as Dark Red Meranti show good durability and reasonable stability for joinery manufacture. If using other forms such as light red Meranti preservative treatment is necessary
  • Some species of Meranti contain, water soluble extractives. On these a stain inhibiting primer or mid coat should be used to ensure the extractives do not discolour the paint finish.
  • Many species contain a coarse grain structure. To avoid problems with air pockets use a grain filling primer or mid coat. Failure to do so may result in bubbles appearing in the dry paint film where air escapes and breaks through the drying surface.

Eucalyptus Grandis

  • This species is designated as durable for joinery manufacture.
  • A consistent supply of material with well controlled moisture content can be obtained.
  • The product has a coarse grain structure. To avoid problems with air pockets use a grain filling primer or mid coat. Failure to do so may result in bubbles appearing in the dry paint film where air escapes and breaks through the drying surface.
  • This species shows good dimensional stability and is used for joinery manufacture throughout the UK.
  • Lighter coloured material is not prone to excessive tannin staining

Sapele (Entandrophragma cylindricum)

  • Very commonly used hardwood in joinery manufacture.
  • Extractives in this species may discolour paint finishes and stain inhibiting primers are recommended.
  • There is a risk of moisture movement and twisting with this timber.
  • Unlike many other hardwoods this species does not have a very coarse grain structure and tends to give a smooth paint finish without the need for grain filling primers and mid coats.

Idigbo (Terminalia ivornsis)

  • Idigbo is a very durable timber suitable for exterior joinery manufacture without preservative treatment.
  • Idigbo contains highly water soluble extractives which exhibit themselves as a yellow/green staining on light coloured paint finishes.
  • Dark tannins will leach out of the timber onto surrounding substrates such as masonry if the timber is not properly coated.
  • Specialist stain inhibiting primers are required when painting this species.
  • The highly acidic tannin content can affect certain binders used in paints and stains due to lowering the pH in dip tanks and flow coaters. Dip tank and flow coater additives are available to counter this issue.
  • Dark staining can occur when ferrous fixings are used by mistake.
  • Coarse grain structure can cause trapped air in drying paint films leading to bubbles.

Iroko (Milicia excels and mregia)

  • This is a very dense timber on which many coating systems dry very slowly due to poor absorption.
  • With certain water-borne dipping primers the binder is so badly affected by extractives on the surface that the stain or paint will not run off.
  • If a suitable degreasing agent is used the coating of this species will be improved and good results can be obtained.
  • This timber has very good stability against movement and is particularly suitable for joinery manufacture.

European oak (Quercus spp)

  • It has excellent durability and has been historically used for exterior joinery for centuries in the UK.
  • This timber is prone to movement that leads to surface checks and splits.
  • Contains water soluble extractives which can result in staining of light coloured paint finishes. It is prudent to use stain inhibiting primers with this species.
  • Dark Brown/black staining can occur when ferrous fixings are used by mistake.
  • Tannin staining at end grains under light coloured translucent finishes can be an issue.