Causes of Rotting Wood
Whenever wood has more than 20% moisture exposure it has the potential to deteriorate. It’s very important to keep up on caulking and painting with quality materials to prevent wood rot.
If you are at the point where you already have wood rot we recommend you do not use pine for rot replacement. Pine available on the market today tends to be new growth pine. Pine available today is not as dense as older growth pine and will rot in a very short period of time. So many home owners are so disappointed to find their new homes have extensive wood rot damage within the first five years.
Painting and caulking are two of the home owners best materials that will help prevent wood rot. Caulking is one of the best defenses your home has against moisture. Home owners should be vigilante for the appearance of peeling or cracking paint and cracked or missing caulking. Either of these are indicators that your wood is now being attacked by moisture. As a home inspector I am always reminding my clients of the old but true adage that ” an ounce of prevention is better than a pound of cure.”
Repairing Areas of Wood Rot
Using a wood chisel, an electric drill with a spade bit, or another tool appropriate for the location to remove all of the wet, loose and decayed wood.
Probe the surrounding area with an awl. If it feels as solid as unaffected areas, drill numerous closely spaced holes of 1/8-inch (3-mm) diameter in the wood and inject a liquid wood hardener following the manufactures directions.
Mix two-part epoxy or polyester wood filler as directed. Mix only what you can apply and shape in a few minutes. Once the material hardens it is un-workable and must be thrown away.
Fill the hole or build up the affected area with the wood filler, using a putty knife or flexible plastic spreader. Press hard on knife to work the initial layer into the surface for a good bond.
Clean off the applicator and mixing container immediately
Use a rasp tool to roughly shape or level excess filler as soon as the filler sets up, but before it dries completely.
Use medium or coarse sandpaper to further shape and blend the patch when the filler is completely dry. On flat surfaces, use a rubber sanding block or power sander. On contoured surfaces, use wood dowels or other appropriate shapes to back the sandpaper.
Blow off the dust and apply freshly mixed filler to fill any remaining depressions or pinholes, or to build up more material as needed to attain the desired shape.
Use medium, then fine sandpaper to smooth the patch and feather it into the surrounding wood.
After completely dry prime and paint to suit.
Choosing Your Exterior Paints
For most exterior wood in reasonably good shape, pick a high-quality acrylic primer. It remains elastic and permeable so moisture can “breathe” through the paint skin. This will decrease the chance of the paint bubbling and peeling due to moisture in the walls.
Consider oil- or shellac-based primers for cedar or redwood. With these, you have to factor in problems with tannin staining. Tannin is a natural substance in the wood which will bleed through and cause yellow or brown stains in your finished paint job. It is water soluble, so it will bleed through any water based product. Oil and shellac primers will stop tannin from bleeding through. Some water-based primers claim to be able to stop tannin staining, although sometimes two or more coats will be necessary. Use your own judgment.
Ask at your paint store about breathable oil primers, which are formulated to allow passage of moisture from the house through the paint. (All water-based products, unless they are sold specifically as moisture-barriers, are breathable.) Breathable oil primers would be your best choice to help combat tannin staining some plywood materials, in addition to cedar, redwood.
Use oil-based primers for very punky, soft older wood. Oil-based primers penetrate much deeper into the wood fibers and create a more solid substrate to paint over.
This article is brought to you by Roger Frost, The Barrie Home Inspector, browse our Home Maintenance Tips Blog for more Money Saving Tips
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