Stained clapboards (C) Daniel Friedman Extractive Bleeding Stains on Building Exterior Walls

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Extractive bleeding stains on wood siding:

Building siding extractive bleeding stain cause diagnosis & cure or prevention.

This article series catalogs the different types of stains or discolorations found on building exterior surfaces: walls, roof, trim, walks, patios, decks, etc.

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Extractive Bleeding Stains or Marks on Building Siding, Walls, Trim

Stained clapboards (C) Daniel Friedman

Cause & Prevention of Extractive Bleeding Stain Problems on Building Exterior Siding

As reported in Best Practices Guide to Residential Construction:

Excess moisture in wood species such as cedar, redwood, Douglas fir, and mahogany can dissolve the natural tannins in the wood and cause them to migrate to the surface, leaving a reddish-brown stain on the finish.

Sealers and stain-blocking primers help to minimize this problem but do not always eliminate it. If staining occurs, the first step is to eliminate the moisture problem.

Then, if the extractive bleeding is mild, remove the stains with a mild detergent and water. More severe cases will require cleaning with an oxalic acid solution.

Carefully follow the manufacturer’s instructions when using oxalic acid, as the bleaching solution will harm plants and may bleach existing finishes on siding, trim, and other woodwork.

After washing, the oxalic acid must be thoroughly rinsed with clean water and the wood dried before finishing or refinishing. If the extractive bleeding has been allowed to bake in the sun, it may have hardened and be difficult to remove. In this case, you will need to apply a stain-blocking primer before refinishing.

Our clapboard staining photo below left shows staining in an inside corner below a roof valley where we suspect there was gutter spillage or leakage down the wall, exacerbating siding staining. Look at the edge of the stains and you'll see some extractive bleeding.

[Click to enlarge any image]

Our stained clapboard siding photo at below right is a closeup of stains found on the home shown in our photograph just above.

Stained clapboards (C) Daniel Friedman

Stains and stain prevention on red-cedar siding are discussed separately

Stained clapboards (C) Daniel Friedman


Continue reading at STAIN DIAGNOSIS on BUILDING EXTERIORS or select a topic from closely-related articles below, or see our complete INDEX to RELATED ARTICLES below.

Or see EXTRACTIVE BLEEDING on SHINGLES extractive bleeding stains on asphalt roofs 

Or see STAINS on & in BUILDINGS, CAUSES & CURES - home

Or see STAINS on RED CEDAR SIDING - more stains on wood siding


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EXTRACTIVE BLEEDING SIDING STAINS at - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.


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