Wood Fence FAQs: Redwood
It's unique to the Northern California coast and adjacent regions. Redwood is harvested in commercial forests from San Francisco to Southern Oregon in a strip along the Pacific Ocean.
What's the difference between nominal and actual thickness?
Nominal is a size designation most lumber uses for convenience. In lumber, the nominal size is usually greater than the actual size.
|1" = nominal||Producers have determined that the|
|3/4" = actual||thinner sizes still have acceptable|
|21/32" = actual||performance. Also, due to rising cost,|
|5/8" = actual||raw-material producers receive a better|
|return with thinner products.|
How does full width differ from scant width?
All lumber is produced with the stated width as the target size. As milling has become more accurate, target sizes have moved closer to surfaced or planed sizes, i.e. 5 1/2". As the width diminishes, the actual width is scant-or less than-the nominal width.
Width: 6", 4", 3" - full width
5 1/2", 3 1/2", 2 1/2" - scant width
Why do knots fall out of boards, creating holes?
Knots and the surrounding wood have different densities. Since knots are denser, they expand and contract less than the surrounding wood, loosening the bond. To protect against this, use a Premium or #1 board with both faces graded. The knots will be smaller and intergrown. The cost is slightly more, but your fence will have a longer serviceable life.
What causes Redwood boards to develop black stains at the nails?
The stain is caused by natural wood extracts interacting with metal in the fastener. Moist wood increases the likelihood of this interaction. For Redwood, Cedar and Cypress, you should use double-dipped galvanized, stainless steel or aluminum fasteners.
Can the stained Redwood be cleaned off?
Yes. If the stain is brownish, use a solution with Trisodium Phosphate (TSP), available at retail hardware stores. If the stain is black, use a solution with Oxalic Acid to clean the boards. This material is also available at retail hardware stores.
Commercial cleaners are available as well. Identify the cause of the stain to ensure you choose the correct product. Certain concrete cleaners are specifically formulated to clean wood extracts from patios, sidewalks, or other concrete structures.
What about using bleach and water?
Chlorine-based or Oxygen-type bleach is effective against mildew and fungi. Oxygen-type bleach contains sodium percarbonate which when added to water forms hydrogen peroxide, an effective agent in removing mildew stains, dirt and weathered gray residue from wood that has ultraviolet (sunlight) degradation. Unlike chlorine-based bleach, once the wood is treated with the oxygen-type bleach it will return to its original natural appearance.
Some species of wood contain tannins, a natural resin. Water can extract these resins from wood leaving brown or black discolorations on the surface. Blue-black stains can result from a reaction of tannins to the iron in nails or fasteners. Neither chlorine nor oxygen bleaches are effective against tannin or iron stains but use of an oxalic acid-based product mentioned previously, will render the stains colorless.
Why do boards split when fastened with nails?
Correct nails and nailing practices are essential to successful installation. Choosing a needle point nail is a common mistake. While the most commonly used nail is a diamond point, a blunt point will reduce splitting. Overdriving nails is another problem that distorts wood and causes excessive splitting. Predrilling will help reduce any splitting that can occur.
The boards at the top of my fence are warping. Why?
The backrails should be no more than 8" from the fence board tops and bottoms. Fence boards 6' long should have three back rails. Spacing your rails this way will help control the wood's natural tendency to warp due to expansion and contraction.
What can be done to eliminate the effects of weathering and keep that "new fence" look?
While there's no way to eliminate the weathering of wood, it's relatively easy to minimize the effects:
- Use three back rails (6' fence), two backrails (4', 5' fence), or 4 backrails (8' fence) for more hold-down points.
- Use only hot-dipped galvanized, or stainless steel fasteners with a ring or spiral shank to minimize warp and rust stains.
- Treat the surfaces of fence boards with a water-repellant solution to reduce the rate that moisture is absorbed and released. This solution should also have a good UV inhibitor if you don't want the fence to gray.
- Follow a regular maintenance program of cleaning and refinishing every few years with a "clear" or "toner" water repellant containing UV inhibitors. This will revitalize a dingy appearance caused by dirt, mildew or graying. It's like washing and waxing your car. Opinions differ on how necessary it is to perform regular maintenance, but most agree your fence will look much better for the effort.