Recommended construction techniques, hardware and maintenance
Whether you hire a contractor or build your project yourself, note: treated wood will last a long time, therefore so will your workmanship. You’ll be happier – and your project will look better – if you take your time and observe the following construction techniques.
- Make sure that your wood is suited for the intended use. Check the tag on lumber for “above ground” or “ground contact.”
- Before you begin, lay out your lumber with the best-looking face exposed. Decide which pieces you want for visible areas, and which pieces for understructure.
- Separate deck boards as follows to allow for expansion and contraction. If heavy and wet, separate boards no more than 1/16″ as some shrinkage will occur. If light and dry, separate boards no more than 1/8″.
- Avoid long spans in construction. The greater the distance between supporting points, the more force developed within the wood as it dries. Also avoid designs with long cantilevers unsecured at one end.
- Orient embedded support columns so only treated ends are in ground contact.
- Cover upper ends of posts with post caps or cut them at angles to shed water.
- For maximum protection, it is recommended to coat cut ends, drill holes, and other imperfections with a topical Copper Naphthenate wood preservative such as Wolman Woodlife Copper Coat or equivalent. Additionally, original factory ends of posts should be put into the ground to insure longest life as cuts in pressure treated lumber may expose untreated material to the elements. Cut ends should not be placed in the ground.
- Use enough screws. Skimping doesn’t pay. Use two screws across a 2 x 4 and three across a 2 x 6. Drive screws at a slight angle toward each other.
- Screws and other hardware should be hot-dipped zinc-coated or equally well protected material. Otherwise, weather may cause them to rust, leaving streaks.
- To reduce splitting, drill a pilot hole about three quarters the diameter of the nail.
- Use 3 1/4” screws on nominal two-inch decking. Use two at each joint with 2 x 4s laid flat; use three for 2 x 6s laid flat. 3″ screws are recommended for 5/4″ decking.
- Lumber wider than six inches should not be used as a flat surface. Wide, flat boards are subject to ponding of rain water, which can lead to cupping problems. It is better to use two 2 x 6’s than one 2 x 12.
- If a board is bowed, install it with the crown up. Gravity and the weight of people and furniture will flatten it.
- If a board has a slight bend to it, it sometimes can be straightened as it is screwed in place.
- Click here for a Mississippi State report on ‘Treating’ Treated Wood.
Hot-dipped galvanized fasteners (meeting ASTM A 153) and connectors (ASTM A 653 Class G185 sheet), or better, are recommended.
For Permanent Wood Foundations and corrosive environments, such as areas with saltwater spray, use 304 or 316 stainless steel. Aluminum should not be used in direct contact with this wood, unless an adequate physical barrier separates the aluminum from the wood or the manufacturer ensures the performance of the aluminum product.
For indoor applications, while galvanized fasteners are preferable, the use of nongalvanized nails or screws of sizes and types approved by the Model Code is acceptable when attaching joists, studs or other framing to Wolmanized® sill plate, provided the wood will remain dry in service, protected from weather and water. Likewise, the use of standard galvanized strapping, anchor plates, or mild steel anchor bolts 1/2″ diameter and larger is acceptable for fastening Wolmanized® wood to foundations, provided that the wood will remain dry in service, protected from the weather and water.
Additional information on the corrosion of fasteners and connectors used with alternative pressure treated wood:
No maintenance is needed to renew resistance to fungi and termites. Wolmanized® wood has a lifetime limited warranty against these organisms. However, protection is required to maintain the wood’s appearance against weather. Sun and rain cycles cause stresses in lumber and result in swelling, shrinking, warping, and cracking.
- To help protect your project against moisture damage, apply an effective brand of water repellent as soon as your outdoor wood project is finished or, for large projects, as sections are completed. Water repellent should be applied every year or two.
- To revitalize a dingy appearance caused by dirt and mildew, use deck brightener to clean the outdoor wood.
- To validate the warranty in some states and for some species, apply an end-cut solution.
Painting & Staining
You can stain or paint Wolmanized® wood. You can also coat this wood with a water repellent; in fact, we highly recommend it. The best way to tackle these jobs depends on the wood you have, its exposure, and the coating you plan to use. Many light-colored latex paints can be used successfully following brush-application of an oil-based primer. Primer should not be applied by sprayer, nor should coatings be used if their manufacturer advises against a primer. Always follow the manufacturer’s directions and take special care in sealing end grain, holes and other penetrations with the primer.
How long must you wait before the wood is dry internally?
The time it takes for wood to dry out depends on the climate and the wood’s exposure. In summer in the American southwest, deck lumber open to sunshine can dry in a few days. In cool, damp weather or when shaded by an overhanging roof or tree, it will take much longer for wood to dry. As a fairly safe average, we recommend waiting six months before applying paint.
Typical treated wood
When wood is pressure-treated, it is saturated with a liquid solution of preservative diluted in water. In a typical situation, the wood you buy is still somewhat damp.
PAINT – Do not apply paint until the wood is dry, both on the surface and internally. Otherwise, as the wood dries out, escaping moisture will cause blisters and poor adhesion in the paint. We recommend a six month waiting period before applying paint (see more below). Once the wood is dry, the procedure for painting treated wood is no different from that for painting untreated wood. Application of a primer is suggested for best results. (We recommend against using paint on deck flooring because frequently used pathways, such as from the steps to the door, will become worn.)
STAIN – Some stains are heavily pigmented and form a film, just as paint does. The recommendations for their application are the same as those for paint, including our advice against using them for the floor of a deck. Most stains, however, are more transparent and do not block moisture movement. There are other differences, though. Stains may be oil-based or water-based. Some formulations can be used immediately; others perform best when the wood is allowed to dry for a while. Best advice: follow the stain manufacturer’s instructions.
WATER REPELLENT – Most water repellent brands say that it is okay to apply a water repellent without delay, which is ideal timing. For other brands, a slight delay is recommended. Again, it is best to follow the manufacturer’s instructions.
Treated wood with built-in water repellent
To protect against moisture damage, some Wolmanized® Outdoor wood has water repellent as well as preservative, as does Thompsonized® Wood. The water repellent slows down the rate at which the wood absorbs and releases moisture.
PAINT & STAIN – The recommendations are the same as above, but it may take longer for the wood to dry out. Therefore, the delay may be longer. For instance, we recommend waiting 30 days before applying an oil-based product to Thompsonized® Wood, and waiting a year before using a water-based stain.
WATER REPELLENT – With water repellent treated wood, an initial coating of topical water repellent is not necessary. For Wolmanized® wood with water repellent, you don’t need a water repellent coating for a year, but apply it annually thereafter.
Treated wood that is re-dried after treatment
In some areas you can buy treated wood that is Kiln Dried After Treatment (KDAT) or Air Dried After Treatment (ADAT). In these processes, moisture is removed from the wood before shipment to a lumber dealer. KDAT or ADAT will be marked on each piece of wood on either the end tag or an ink stamp.
PAINT, STAIN, WATER REPELLENT – The moisture content of the wood is already in balance with atmospheric moisture levels, so coating can proceed immediately.