Most rotted porch posts fail at the same spot: the bottom 6 inches, where end grain sits on concrete and wicks water every time it rains. Cedar porch posts resist decay naturally and look far warmer than treated lumber, but even cedar rots if it sits directly on a wet slab. The right post is a combination of species, size and a raised standoff base. For most covered front porches, a 6×6 cedar post on a galvanized standoff base with a penetrating finish is the best balance of strength, looks and lifespan.
Choosing among cedar, pressure-treated pine and Douglas fir depends on whether the posts are exposed to weather, whether they will be painted, and how much load they carry. Size is just as important. A 4×4 porch post that looks fine on a drawing can look spindly on a real house and may not carry a long beam span. This is a material and sizing decision, so start with the job the post has to do.
Why Choose Cedar Porch Posts
Western red cedar contains natural oils and extractives that slow decay and repel insects. It is lightweight, stable, and less prone to checking and twisting than many softwoods. It takes stain beautifully and weathers to a silver gray if left unfinished. Those traits make cedar the favorite for exposed wood porch posts where the grain shows.
Cedar’s weaknesses are softness and price. It dents more easily than fir or pine, and its natural rot resistance is strongest in the heartwood; sapwood is lighter in color and much less durable. Large-dimension cedar such as 8×8 timbers can be expensive and harder to find without checks. Still, for a front porch where appearance matters, cedar porch posts pay for themselves in looks and reduced maintenance.
Cedar vs Treated Pine vs Fir
| Material | Rot resistance | Best finish | Relative cost |
|---|---|---|---|
| Western red cedar | Good (heartwood) | Stain or clear oil | Higher |
| Pressure-treated pine | Very good (ground-contact rated) | Paint or solid stain after drying | Lowest |
| Douglas fir | Low untreated | Paint, covered porches only | Moderate |
Pressure-Treated Pine
Treated southern yellow pine is the structural workhorse. Ground-contact rated posts carry the highest preservative retention and resist rot even in direct soil contact. The trade-offs: treated pine arrives wet, shrinks and checks as it dries, often twists, and has a green or brown cast that most people paint or stain. For a painted front porch post, treated pine is perfectly good once it has dried for several weeks to a few months. Use hot-dip galvanized or stainless fasteners, since modern treatments corrode plain steel.
Douglas Fir
Fir is strong and straight, which makes it popular for turned porch posts and colonial porch posts with milled details. Untreated fir needs protection, so it belongs on covered porches with paint on every face, including the cut ends. Many traditional turned and colonial styles come in fir or poplar and are meant to be painted.
Cedar
Cedar sits in the middle: natural durability without chemical treatment, excellent looks under stain, and less movement as it dries. It is the clear choice when you want a stained natural look on a porch with wooden posts.
Sizing: 4×4, 6×6 or 8×8
Nominal sizes are smaller than they sound. A 4×4 measures about 3-1/2 by 3-1/2 inches, a 6×6 about 5-1/2 by 5-1/2, and an 8×8 about 7-1/4 or 7-1/2 inches square depending on the mill.
- 4×4 porch post: Fine for railings, small stoops, light pergolas and posts that are later wrapped in a column cover. Most building codes and design guides now steer away from 4×4 posts as the main roof support on new porches.
- 6×6 porch post: The standard for covered porches. Strong enough for typical spans and allows proper notching for beams. Visually it suits most one-story homes.
- 8×8: Used on large porches, two-story homes, heavy timber designs and Craftsman or farmhouse styles where chunky posts look right. Also helpful where a beam spans farther than usual.
Load matters more than looks. Post size, beam size and spacing all work together, and snow loads in northern climates can be considerable. Your local building department or a structural engineer should confirm sizes for a new porch roof. On an existing porch, replace a post with one at least as large as the original.
For proportion, many designers aim for the post width to be roughly 1/12 to 1/10 of its height. An 8-foot post looks balanced at 6×6 or larger. Front porch posts that look too thin are one of the most common complaints on new builds and flips.
Preventing Rot: Bases, Caps and Finishes
Use a Standoff Base
The single most important step is lifting the post end grain off the concrete. A galvanized post base with a 1 inch standoff lets water drain away and air reach the bottom of the post. It also anchors the post to the slab or footing to resist uplift and lateral movement. Bases come in sizes matched to 4×4, 6×6 and 8×8 posts, and many adjust slightly for alignment. If you want the hardware hidden, a trim collar or plinth can wrap around the base while still leaving a drainage gap.
Seal the End Grain
Cut ends absorb water many times faster than face grain. Brush end-grain sealer or a heavy coat of your chosen finish on both ends of every post, including the top, before installation. On treated lumber, apply a cut-end preservative to any fresh cut.
Cap the Top
Exposed post tops on railings or open beams should have a cap or a slight bevel so water runs off. Under a roof, the beam usually protects the top.
Choose a Finish
For cedar, a penetrating oil-based semi-transparent stain shows the grain and is easy to refresh every 2 to 4 years. Film-forming clear finishes tend to peel in sun. For pine or fir, prime all six faces and use two coats of exterior acrylic paint. Avoid trapping moisture under paint by letting treated lumber dry first.
Replacing a Porch Post Step by Step
Replacing a support post means the roof load has to go somewhere while the post is out. Done carefully, it is a manageable project for an experienced DIYer on a single-story covered porch.
Tools and Materials
- New post (cedar, treated pine or fir) and a matching galvanized standoff base
- Adjustable steel shoring post or a doubled 2×6 temporary support
- Bottle jack or screw jack, scrap blocking
- Circular saw, reciprocating saw, drill and masonry bit
- Concrete anchors or wedge anchors, structural screws or bolts
- Level, tape, end-grain sealer, safety glasses and gloves
- Shore the beam. Place temporary supports on solid footing on both sides of the post, close to it but clear of your work. Raise them just enough to take the load off; lifting too far can crack drywall or ceilings inside.
- Remove the old post. Cut or unbolt it at the top and bottom. Check the beam and slab for rot or cracks while they are exposed.
- Install the base. Mark the post center, drill the slab, and set the galvanized base with the anchors specified by its maker.
- Cut the new post. Measure from the base standoff to the beam underside and cut square. Seal both ends.
- Set and fasten. Slide the post in, check plumb on two faces, then fasten to the base and to the beam with the hardware listed for the connection.
- Release the shoring slowly. Lower the jacks gradually, confirm the post is carrying load and still plumb, then remove the supports.
Work on a stable ladder set on firm, level ground, and keep three points of contact when fastening at the beam. Call 811 before digging any new footings. Porch roofs over 1 story, sagging beams, or posts that carry a balcony are jobs for a licensed contractor.
Troubleshooting Common Problems
Post bottom is soft or black. Rot has started from the end grain. Replace the post, add a standoff base, and correct any slab slope that ponds water at the base.
Large cracks or checks. Some checking is normal in solid posts, especially large cedar and treated pine. It is cosmetic unless cracks run through. Box-heart posts (pith centered) check less visibly if the face with the pith faces away from view.
Post is twisting. Treated pine twists as it dries. Choose straight stock and fasten top and bottom securely; a column wrap can hide minor twist.
Paint peeling at the base. Moisture is getting into end grain. Reseal the bottom and consider lifting the post onto a standoff.
Costs and When to Call a Pro
An 8-foot cedar 6×6 typically costs $60 to $150, a treated pine 6×6 about $30 to $70, and an 8×8 cedar timber $150 to $350 or more. Turned porch posts in fir or poplar run roughly $150 to $500 each. A galvanized standoff base adds $20 to $60. Hiring a contractor to replace a single structural post usually costs $300 to $1,000 including shoring, and a full set of new covered porch posts with bases and finish often lands between $1,500 and $5,000.
Bring in a pro or engineer if the beam sags, if multiple posts are rotted, if the porch roof ties into a second story, or if your area has heavy snow or wind loads. New porches need permits in most areas, and HOAs may regulate post size and finish color. A properly sized cedar post on a raised base will outlast several paint jobs on the house around it.
Frequently Asked Questions
Are cedar porch posts better than pressure-treated pine?
Cedar looks better stained and moves less, while treated pine is cheaper and more rot resistant in ground contact. Choose cedar for a natural look and treated pine for painted or budget projects.
What size post do I need for a covered porch?
A 6×6 is the typical choice for a one-story covered porch. Larger porches, longer beam spans and heavy snow areas may need 8×8 posts. Confirm sizing with your building department.
How do I keep wood porch posts from rotting at the bottom?
Mount them on a galvanized standoff base that lifts the end grain off the concrete, seal the cut ends, and make sure the slab slopes water away from the post.
Can a 4×4 support a porch roof?
Only for very small, light structures. Most covered porch roofs call for 6×6 posts, and 4×4 posts are better suited to railings or as a core inside a column wrap.
Should I stain or paint cedar porch posts?
Most homeowners stain cedar with a penetrating semi-transparent finish to show the grain. Paint works too, but prime every face first and refresh the topcoat as it wears.
