The post is the structural backbone of an outdoor shower. Get the depth and concrete work right, and the shower stands solid for 20-plus years. Get it wrong and the post rocks, rots, or heaves out within a few seasons.
Why Pressure-Treated Lumber
Standard dimensional lumber rots in ground contact within a few years. Pressure-treated lumber is infused with preservative under pressure — the treatment rating determines service life. For shower posts set in concrete, use lumber rated UC4B (ground contact, severe conditions) or UC4C (in-ground, fresh water contact). The rating is stamped on the end of each board.
Post Depth
The standard rule is 1/3 of the total post length. A 9-foot post needs a 3-foot hole, leaving 6 feet above grade. In freeze-thaw climates, the bottom of the post or its concrete footing must sit below the local frost line to prevent heaving — frost depth ranges from 0 inches in the deep South to 60-plus inches in northern states. For most outdoor shower posts, use a 10-foot 4x4 or 6x6 pressure-treated post set in a 40–42-inch hole. See our comparison of cedar vs stainless steel shower posts for structural material choices.
Tools and Materials
Post hole digger or rented power auger (recommended for holes over 24 inches), digging bar, two 60-lb bags of fast-setting concrete per post, a level, two wood braces and stakes, water, and a margin trowel. Three inches of washed gravel in the hole bottom is optional but improves drainage around the post base.
Step-by-Step: Setting the Post
1. Dig the hole 6 inches deeper than your target post depth — 3 inches for gravel plus margin below the frost line. 2. Add and compact 3 inches of washed gravel. 3. Lower the post and prop with braces. Check plumb on two adjacent faces and adjust braces until the post reads perfectly vertical on both axes. 4. Pour fast-setting concrete dry into the hole, then add water per package directions — no mixing required. Crown the top of the concrete slightly above grade to shed water away from the post. 5. Hold the post for 20 minutes while concrete begins to set. Recheck plumb at 10 minutes — you can still adjust. Fast-setting concrete reaches working strength in 20–40 minutes; full cure in 24 hours.
Post Cap and Finishing
Cut the post to final height after 24 hours. Trim the top at a slight angle or install a metal post cap to prevent water pooling on the end grain. For hardware to attach fixtures to the post, see our outdoor shower fixtures guide.
Frequently Asked Questions
- How deep should an outdoor shower post be set?
- 1/3 the total post length, with the bottom of the hole at or below the local frost line. A 10-foot post typically needs a 40–42-inch hole in most of the continental US.
- How much concrete do I need for a shower post?
- Two 60-lb bags of fast-setting concrete per 4x4 post in a 10-inch diameter hole at 40-inch depth. Use three bags for a 6x6 post or a wider hole.
- Fast-setting or regular concrete for post setting?
- Fast-setting is preferred — pour it dry and add water in the hole. It reaches working strength in 20–40 minutes versus 24–48 hours for regular concrete, with equivalent results for this application.
- How long before I can attach fixtures to a new post?
- Wait a minimum of 24 hours after pouring concrete before attaching hardware or applying lateral load. Full cure takes 28 days, but working strength is reached in 24 hours with fast-setting mix.