No easy way to remove water stains from cedar

Hey there, time traveller!
This article was published 25/11/2003 (8059 days ago), so information in it may no longer be current.

QUESTION — Our bathroom is paneled with “tongue and groove” knotted cedar. Over the years, lots of water spots have become visible on the wood around the toilet. How can I remove these? Do I have to sand them off? What grade and type of sandpaper? Which oil would I use afterwards to match the general darker colour? Or is there an easier way of getting rid of those ugly spots?

— Gitta Fricke

ANSWER — The possibility and practicality of removing water spots from the cedar around your toilet depends a lot on the finish currently on the wood and the severity of the damage. If the wood is untreated and the spots are mainly on the surface, they may be removable. If the wood is finished and the spots have penetrated deeper into the cedar, removal will be difficult to impossible. If oil or varnish is the suspected finish, the approach for cleaning the stains will be different than untreated wood.

For suggestions and a professional opinion, I consulted journeyman painter Don Moulden of Moulden Painters and Decorators. The first case scenario we will explore will assume that the paneling is untreated. In this instance, Moulden suggests starting with methyl hydrate in an attempt to remove faint surface stains. This weaker solvent may provide some help in removal of the stains and should not damage the wood. Moulden emphasizes that this is only the first step and may do little to help if the stains are deeper in the wood. If the “water spots” you describe are lighter grey and faint, this first method may be sufficient to allow refinishing.

If methyl hydrate does little, wood bleach is available that can be used to lighten the entire area to allow for refinishing. Moulden cautions that bleaches are difficult to use and are normally employed by professionals. Bleach may be applied to small areas with a Q-tip or very small applicator and will require practice.

If the stains are dark grey or black , they may be deeper into the wood and may not be removable. In this case, removal and replacement of the damaged boards is the only alternative. If the stains are black and more extensive in coverage, there may also be rot in the wood, ensuring that removal is the only choice. This is more likely in areas around the bathtub or shower, but may also be present around the toilet. The benefit of this type of wood paneling is that individual boards may be replaced, providing identical replacement paneling can be found.

If the cedar boards are finished using an oil or varnish, sanding will be needed to remove the spots. If the stains are mostly on the surface, sanding with a medium to fine grit sandpaper, to remove the outer layer, may be sufficient. If the stains are deeper, heavier sanding and wood bleach may be required to allow for proper rejuvenation of the wood.

Many interior finishes are available for cedar, with the most common being Danish Oil, or similar penetrating oil finishes. These finishes contain minimal solids, compared to varnishes or urethanes, and allow the pores in the natural wood to breathe. They will, however, provide some moisture resistance and may be ideal for interior finishes such as those in your bathroom. Danish oil will dry out over a period of months and years and regular reapplication is necessary to maintain the finish.

Moulden recommends refinishing with Danish oil after removal of the stains. He states that the best method for refinishing is to apply the oil directly and work the finish into the wood using very fine grade sandpaper. Moulden cautions that only wet-dry sandpaper is appropriate for use in a grade of approximately 200 to 400 grit. The sandpaper will help the oil penetrate properly and will give a smoother surface and slight shine to the wood after application. Once the oil application is complete and allowed to partially dry, the excess oil on the surface can be removed with a dry, clean rag.

Ari Marantz is the owner of Trained Eye Home Inspection Ltd. and the Vice President of the Canadian Association of Home & Property Inspectors (www.cahi.mb.ca). Questions can be e-mailed or sent to: Ask The Inspector, P.O. Box 69021, 110-2025 Corydon Ave., Winnipeg, MB. R3P 2G9. Ari can be reached at (204) 291-5358.

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