Deck and fence staining in a desert climate

A deck in this valley takes more punishment than the siding right beside it, and the reason is orientation. It lies flat, so it takes the overhead summer sun directly rather than at a glancing angle, holds snow for weeks instead of shedding it, gets walked on, and dries out hard in air that spends most of the year at low humidity. Cedar and pine left unfinished turn silver-gray within a season or two, and film-forming products laid over weathered wood peel away in sheets.

Why stain and not paint

Paint and heavy film-forming coatings sit on top of the wood. On a vertical wall that works fine. On a horizontal deck board it fails, because water pools, freezes, and lifts the film from beneath, and foot traffic abrades what is left. Once a film starts peeling on a deck the only real fix is stripping the whole surface, which is the most expensive maintenance path available.

Penetrating and semi-transparent stains soak into the wood instead. They wear by gradual fading rather than peeling, which means the maintenance coat is a wash and a recoat rather than a strip and rebuild. That difference is why stain is the default recommendation for horizontal wood here.

The finish options

• Penetrating oil / clear sealer: minimal color change, shortest cycle, easiest recoat. Good on newer wood you want to keep looking natural.
• Semi-transparent stain: the workhorse. Adds color and UV-blocking pigment while letting grain show. Pigment is what protects against UV, so more color generally means longer life.
• Solid-color stain: opaque, hides weathered and mismatched boards, keeps texture visible. The right step for older decks past the point where a transparent finish flatters them. It behaves more like a film, so it is better on rails and fences than on high-traffic deck floors.

What has to be true before wood will take stain

Stain protects by going into the wood, so everything ahead of it is about giving it somewhere to go and something worth going into.

• The surface has to be wood rather than what is sitting on the wood. Dirt, mildew, and the loose gray layer of oxidized fiber on weathered boards are all things a stain would soak into instead of the wood. An oxalic-acid brightener lifts the gray away and takes the tone back close to the original. Leave it and the gray is sealed in underneath, permanently.
• Any old film has to be gone. A penetrating stain cannot get past a peeling solid stain or paint; it can only sit on it. Stripping is an entire additional stage of work, which is why two decks of similar size can price a long way apart.
• The pores have to be empty. Wood still holding water from rain or from the wash has nowhere to put the stain and spits it back out. Salt Lake's dry air closes that gap quickly, which is one of the few things about this climate that works in your favor.
• Pressure has a limit. Washing is effective and easy to overdo: high pressure on soft wood raises the grain and leaves a furred surface that then drinks unevenly and looks blotchy afterwards.
• Stain sitting on top is not stain. Sprayed and left alone, it forms a film on the surface rather than entering the grain, and the grain is where the protection lives. Worked in, it fades. Left on top, it flakes.

Recoat intervals in this valley

• Deck floors in full sun: every 2 to 3 years with semi-transparent stain
• Shaded or covered decks: 3 to 4 years
• Fences and vertical surfaces: 4 to 6 years
• Rails and horizontal caps: closer to the deck-floor interval, since they take sun and snow the same way

These are shorter than the intervals quoted in humid, shaded climates, and the reason is the altitude UV load plus freeze-thaw. The upside is that a light maintenance coat applied on schedule is inexpensive; the cost only escalates once the finish has fully failed and stripping enters the picture.

What it costs

• Single-level deck with a sound existing finish: $800 to $1,800
• Large or multi-level deck, or heavy stripping: $1,800 to $3,800
• Fence: $4 to $8 per linear foot depending on height, condition, and one or two sides

Timing

Late spring through early fall, with the same surface-temperature problem as painting and one of its own. A board baking in afternoon sun is hot enough that the carrier flashes off before the pigment has traveled anywhere, so the stain ends up on the surface rather than in it. At the other end, a board still wet from rain or from the wash has its pores full and cannot take stain either. Both conditions come and go through a single Salt Lake summer day, which is why the dry stretches between monsoon afternoons are the useful ones.

When wood is past finishing

Boards that are cupped, split through, soft at the fasteners, or rotted at the posts are a carpentry problem rather than a finish problem. A stain changes the color of a failing board without changing anything about why it is failing, and it hides the evidence while it does it. Posts are the ones worth looking at first, since they meet the ground and the ground is where the water is.

For the climate mechanics behind these intervals, see the UV guide and the freeze-thaw guide.