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Painting The Exterior(Continues)Stripping exterior paints: Do not strip paint unless you must; scraping will suffice for most exteriors. You must strip, however, if existing coats are too thick; the thickness can usually be determined by checking with your eye and using common sense, especially where paint has cracked down to the wood’s surface. Take a ;en knife or a scraper and dislodge a chunk of paint; anything greater than 15 to 20 mils is too thick to apply more paint on top. (By comparison, most polyethylene sheet plastic is 3 mils thick.) Scaffolding is imperative for large jobs. Your choice of paint strippers is similar to that for interior work: sanders; chemicals, water-based or solvent; heat gun or open-flame torch. Sandblasting is another, less plausible possibility. Sanders: Sanders are not good strippers for most people because they can cut into wood siding too quickly, and you need strong arms to run all day. Such tools are totally unsuitable for sanding detail woodwork. Smaller sanders (orbital or rotary) are very useful after you’ve removed most of the paint with another method. Use No. 30 to No. 60 sandpaper (medium coarse) for most exterior finish sanding. Chemical Strippers: Chemical strippers are an effective but expensive way to strip something as large as a house. Since ventilation is rarely a problem, you can use some of the nastier solvent-based strippers outside; but wear a respirator mask, goggles, and long-sleeved shirt and gloves anyhow. As a stripper, methylene chloride is good; it’s water-based and gentle on wood. Use it with a wallpaper steamer, as described for painting interiors. Chemical strippers are particularly appropriate where delicate trim or detail work is involved. Allow the stripper time to work- at least 10 minutes, and possibly 15. Open-Flame Torch: An open- flame torch is probably the fastest stripper and is a favorite of professionals. Burning, can, however, produce toxic fumes, char wood (adversely affecting the adherence of paint unless the wood is well sanded afterward), and can cause dry materials inside the walls to ignite. Keep the flame moving, scraping as soon as the paint bubbles. Have a fire extinguisher handy. Note: Avoid inhaling the fumes of lead-based paints; a respirator mask with changeable filters is imperative. Heat Gun: A heat gun (or heating iron) isn’t as effective as an open-flame gun but is much safer. The technique is similar hold the heat until the paint bubbles, then scrape. Remember that no heat stripper is completely safe; even no-flame models can cause a fire within a wall; always follow operating instructions scrupulously. Sandblasting: Sandblasting is not advisable for amateur use nor, on most surfaces, by professionals: it removes paint alright, but the method is highly destructive to any surface underneath. It pits and scars wood, destroying its water shedding ability; fine detail is obliterated. Think twice about sandblasting painted brick, too; those walls were probably painted to begin with because their mortar was fatigued. Sandblast, and you will have to repoint as well. Whatever stripping method you choose, strip during a dry period. By tacking sheet plastic along the eaves, you will have an emergency tarp to roll down should there by a storm. Avoid exposing old wood to the weather for any period of time. Once the face has been stripped, prime and paint it at once. Before painting, make sure the surface has been rinsed and is free of chemicals and that is it dry. Stripping a house is a big job; you may want to do only one side of the house each summer. Finally, to reiterate an important point: cover the ground and shrubs with tarps; the debris from stripping paint is messy. It’s also voluminous. Therefore, clean tarps at the end of each working day and cart away the debris.
Exterior PaintThe chose of exterior paints is considerable, including specialty ones such as asphalt-based coatings for built-up roofs and metal roofs; deck enamel for porches; paint for canvas awning; silicone-based preservatives for shake and shingle roofs, mildew-resistant paint and so on. Consult your supplier if you have a special need. The alkyd family of paints is the workhorse of exterior painting, just as it is for interior painting, because of its superior adhesion. Even when a topcoat is latex, professionals often prime with an alkyd primer. Painting over preservatives: Generally, it’s not advisable to paint over preservatives. If something needs preserving, it’s better to apply preservative and reapply it periodically. In hot, humid regions, though, sills, splashboards, lower courses of siding, and porches may preserved and painted, so they will match the rest of the exterior. Probably the best thing to do is buy Wolmanized lumber, which has preservative pressure-treated into it during manufacture. Such wood can be painted over with fairly good results. Preservatives borne in a metal base such as Cuprinol (copper-based) are somewhat less durable as preservatives but are acceptable as undercoats once they are dry. Creosote and penta are very effective preservatives, but they are too oily to hold a covering of paint. The final arbiters of the compatibility of a preservative are the paint manufacturers. The labels on paint cans display the information. Most preservatives are highly toxic, so handle them carefully.
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