Restoring discoloured uncoated timber cladding

There has been an increasing trend to use uncoated wood cladding as the exterior facade to new building projects, both domestic and commercial. Such facades can provide an attractive, long-lived and above all, natural alternative to man-made cladding options.

Uncoated cladding has been used primarily because of its low maintenance requirement on account of the absence of a decorative finish. Many architects choose to specify uncoated cladding because they want the wood to weather to a silver-grey appearance in order to meet their design aims.

This report is based on a two-year ongoing TRADA research project focusing on cladding. There has been an increasing trend to use uncoated wood cladding as the exterior facade to new building projects, both domestic and commercial. Such facades provide an attractive, long-lived and above all, natural alternative to manmade cladding options. However, occasionally problems with surface disfigurement arise which can alter the appearance of the cladding and may detract from its aesthetic impact. The research team has identified a number of effective methods of remedying its occurrence which are outlined in the summary.

Contents:

• Introduction
• Principal causes of discoloration
• Black discoloration
• Extractive staining
• Cleaning trials
• Treatment options
• Case study
• Pressure-washing
• Re-colonization
• Recurrence of staining
• Future developments