Redwood and Cedar: How to Care for Them

Walk the back yards of Bonita, Santee or the older streets of San Diego and you will see the same two woods again and again: redwood and western red cedar. Fences, gates, patio covers, siding, the trim on a Craftsman bungalow. They were chosen for a good reason. Their heartwood carries natural compounds that slow rot and discourage insects, which is exactly what you want from wood that lives outdoors.

Those same compounds are what make the two woods behave differently from the pine and fir most people picture when they think of lumber. If you know what redwood and cedar are doing, you can keep them looking good for a long time. If you treat them like any other board, they will let you know.

What makes redwood and cedar different from other wood?

Both are softwoods rich in extractives: natural oils, resins and tannins that give them their color, their scent and their resistance to decay. They are also light and fairly soft, with an open grain. The extractives decide how finishes behave on them, and the softness decides how carefully they must be cleaned and sanded before anything goes on.

Heartwood and sapwood are not the same wood

Look at the end of a redwood board and you will often see two colors: a deep reddish-brown core and a pale cream band near the bark edge. The dark part is heartwood, where the protective extractives are concentrated. The pale part is sapwood, and it has very little of that natural protection.

This matters on your property. A fence built from mixed grades will have boards, or parts of boards, that weather and soften years ahead of the rest. Sapwood takes stain differently too, usually lighter and more absorbent, so a fence can look striped after staining if no one accounts for it. On a fence or a pergola, the sapwood boards and the cut ends are the first places to check for soft spots.

Tannin: the color that moves

Tannin is water-soluble. Whenever redwood or cedar gets wet (rain, the sprinklers, the marine layer settling on it overnight), some of that tannin moves toward the surface and can leave tan or reddish-brown streaks on whatever is next to it or on top of it.

Two places you will notice it:

• Under a light paint. Paint white trim over raw cedar without the right primer and brown blotches will come through, sometimes within days. If you want redwood or cedar painted, it needs a stain-blocking primer first. Both Dunn-Edwards and Sherwin-Williams make primers designed for this.
• Under a clear or very light stain. Clear and transparent finishes let the wood’s own color show, and that includes the extractives moving within it. This is one reason clear finishes on these woods need refreshing more often than pigmented ones.

The black stains around nails

If your redwood fence has dark gray or black halos around every nail or screw, the cause is chemistry rather than dirt. Tannin reacts with iron. Ordinary steel fasteners, and even fine steel particles left by a wire brush or steel wool, set off a reaction that turns the wood dark in the area around them. Moisture speeds it up, so it is worst near irrigation and close to the coast.

Preparation can usually lighten these stains a good deal. But if the fasteners stay as they are, the stain comes back. On new work, stainless steel or properly coated fasteners avoid the problem. On existing work, it is worth knowing about before you pay for a new finish, so you understand why the marks may return around the nail heads.

Soft wood needs a gentle hand

Redwood and cedar are soft enough to dent with a fingernail. That softness also means they are readily damaged when cleaning. A pressure washer set too high, or held too close, tears the surface fibers and leaves the board fuzzy and furred. Those raised fibers drink stain unevenly, look blotchy, and break away sooner.

Sanding has the same trap. Coarse paper or an aggressive sander leaves swirl marks that a stain will highlight rather than hide. Good sanding goes along the grain, with the right paper, and it takes the time it takes.

New lumber is not ready on the day it is built

A brand-new redwood or cedar fence looks ready to stain, but often it is not. Lumber can leave the mill with a smooth, compressed surface sometimes called mill glaze, which resists penetration. The wood may also still be carrying moisture from the yard.

Stain applied too soon tends to sit on the surface, look uneven and wear off in patches. The wood is checked first, and a few drops of water on the surface tell you a lot: if they soak in, the wood is ready to accept a finish; if they bead and sit, it is not yet. Preparing the surface opens it up so the stain goes into the wood rather than lying on top.

The silver-gray patina

Left unfinished, redwood and cedar turn silver-gray. That color is sunlight breaking down the lignin in the surface fibers, and in the inland sun of Santee it happens sooner than in a shaded Bonita yard. Some homeowners like the look, and that is a legitimate choice.

What the gray means for a finish is the part people miss: that top layer is weak and loose. Stain applied over it bonds to fibers that are already letting go. If you want color back, the gray has to be cleaned off first, down to sound wood.

Choosing a finish for these woods

Because the extractives keep moving, penetrating finishes that soak in tend to suit redwood and cedar better than thick films that sit on top and can be pushed off from beneath. More pigment generally means more protection from the sun, at the cost of showing less grain. A film-forming paint is possible too, and sometimes right for trim, but only over a stain-blocking primer.

That choice starts with your wood: its grade, its condition and how much sun and water it gets. More is on the wood staining service page, and on how the climate shapes the job in Bonita, Santee and San Diego.

Let someone look at your wood

Redwood and cedar repay the care that goes into them, and they show every shortcut. Ebenezer has more than a decade in the trade and treats a fence board with the same attention as a front door, because, in his words, “Paint to me is an art.” He uses Dunn-Edwards and Sherwin-Williams products, manages every job himself, and if something is not right afterwards he comes back and repairs it.

If your fence has gone gray, your patio cover has black streaks at every bolt, or you are not sure what that new cedar needs, ask for a free estimate. He will look at the wood itself and tell you plainly what it needs.