Maintenance is an item that needs to be considered at the design stage and is discussed in detail in The Timber Service Design Guide available for download below. When deciding on the quality of elements and fittings that will be specified for a newly designed structure, a designer frequently chooses between items that have relatively high initial costs and low ongoing maintenance requirements and items that are cheaper to purchase but may have more onerous maintenance requirements. In some design briefs, the designer is called upon to devise a maintenance schedule for the completed structure. The Table below gives a list of the items that may need to be considered when drawing up a maintenance schedule.
The key to the durability of timber has already been identified as "keeping it dry". Most of the maintenance requirements outlined in the Table lead to the exclusion of moisture from the timber. Others are concerned with the integrity of barriers that control infestation by termites. The Table provides guidance only, as fittings, coatings and barriers of different qualities and characteristics can be installed and the manufacturers may recommend different maintenance intervals. As well, exposure to sunlight, chemicals, salt, and water may vary with the service environment and all of these affect the maintenance regime required.
|
Item |
Maintenance or Inspection Period |
Remarks |
|
Finishes ‑ internal ‑ external |
~ 10 to 15 years see Table 1.9 |
|
|
Cleaning |
Clean non-confined surfaces as required. Remove build-up of soil against timber near to ground. |
Dirt, mould etc traps moisture, increases potential for decay. |
|
Cladding roofing, weatherproofing |
~ 10 year inspections some environments may make inspection of weatherproofing more frequent |
Timber cladding can have design life (5 to 100 years) |
|
Termite protection ‑ physical barriers ‑ chemical barriers |
inspect annually or in accordance with <AS3660> ~ 10 years for maintenance of barrier as required by supplier (~2 to 20 years) |
Any sign of termites should prompt action |
|
Ventilation subfloor, wall, roof |
Check that vents are not blocked ~ annually or after any new work Clean as required ~ 10 years |
Vents are essential to prevent build up of moisture/condensation |
|
Vapour barriers subfloor, roof |
Check integrity ~15 years or after any new work or other maintenance in the area |
|
|
Metal fasteners ‑ integrity ‑ corrosion |
Retighten bolts, screws and repunch nails if req'd after 6 months and one year if unseasoned timber used Check at intervals dependent on type of corrosion protection used. Inject water repellents for bolts. |
Replace any suspect fasteners. Hot dipped galvanised fasteners solve many corrosion problems. |
|
Plumbing |
Inspect gutters, downpipes etc 10 years Repair any plumbing if a leak is noticed |
Moisture accelerates decay, deterioration |
|
Decay |
Check at the same time as connections Repair or replace as soon as any decay is noticed |
|
|
End-grain ‑ sealants/caps |
Inspect 3 - 5 years Replenish as required by manufacturer and before repainting |
|
This Table gives guidance on the maintenance of paints and stains for exterior surfaces. There are significant differences in the expected life of the various coating systems and these can influence the type of coating system selected. Note that clear finishes have a much shorter life than opaque finishes.
|
Finish |
Appearance |
Initial treatment |
Maintenance of surface finish a |
|||
|
|
of wood |
|
Cost |
Procedure |
Period |
Cost |
|
Paint |
Grain and natural colour obscured |
Prime and two top coats |
Medium to high |
Clean and apply top coat or remove and repeat initial treatment if requ’d |
7 ‑ 10 years b |
Medium |
|
Clear |
Grain and natural colour unchanged if adequately maintained |
Four coats (minimum) |
High |
Clean and stain bleached areas and apply two more coats |
2 years or when breakdown begins |
High |
|
Water repellent c |
Grain and natural colour - visibility becoming darker and rougher textured |
One or two coats of clear material, or preferably dip applied |
Low |
Clean and apply sufficient material |
1 ‑ 3 years or when preferred |
Low to medium |
|
Stains |
Grain visible, coloured as desired |
One or two brush coats |
Low to medium |
Clean and apply sufficient material |
3 ‑ 6 years or when preferred |
Low to medium |
|
Organic solvents preservatives d |
Grain visible, coloured as desired |
Pressure, steeping, dipping, brushing |
Low to medium |
Brush down and reapply |
2 ‑ 3 years |
Medium |
|
Waterborne Preservatives |
Grain visible, greenish, fading with age |
Pressure |
Medium |
Brush down to remove surface dirt |
None unless stained, painted or varnished |
Nil |
Legend:
a This table is a compilation of data from the observations of many researchers
b Using top quality acrylic latex paints
c With or without added preservatives. Addition of preservative helps control mildew and mould.
d Pentachlorophenol, tri-n-butyltin oxide, copper naphthenate and similar materials.