How To Make A Garden Bench With Cast Iron Ends | Weekend Build Plan

Want a sturdy outdoor seat that fits your space? Those cast-iron side frames at markets are ideal. They’re strong and give a classic look without tricky joinery. This guide covers planning, sizing, parts, and a clean build from scratch or by re-slatting an old frame. You’ll see clear measurements, a simple cut list, and finish tips that hold up through the seasons.

Bench At A Glance

Before cutting, dial in size, timber, and fasteners. Use the ranges below to tune comfort and durability.

Part Or Setting	Target Range	Notes
Seat Height (floor to top)	16–18 in (405–455 mm)	Feet rest flat.
Seat Depth (front to back)	15–18 in (380–455 mm)	Support without pressure.
Seat Width	36–60 in (915–1525 mm)	Two to three seats.
Backrest Lean	10–15° from vertical	Relaxed posture.
Slat Thickness	3/4–1 in (19–25 mm)	Stiff at common spans.
Slat Width	1½–3½ in (38–90 mm)	Narrow slats shed water.
Fasteners	Stainless or hot-dip galvanized	Rust resistance.
Lumber Choice	Durable hardwood or treated softwood	Pick for weather and budget.

Build A Garden Seat With Cast-Iron Ends: Core Steps

The metal sides do the heavy lifting. Your job is to connect them with wood that fits, feels good, and resists weather.

1) Prep The Metal Sides

Check for cracks near bolt holes. Remove old slats and hardware. Wire-brush to bright metal, wipe with mineral spirits, spot-prime pits, then coat with exterior metal paint or enamel. Add thin rubber pads to the feet so the bench won’t rock on pavers.

2) Pick Wood That Lasts Outside

Cedar, white oak, iroko, and teak do well outdoors. Pressure-treated pine is a value option. Where parts sit near damp ground or trapped joints, treated stock labeled for the right exposure class resists decay. The American Wood Protection Association’s Use Category System outlines common outdoor use levels (UC3 above ground; UC4A ground-contact risk).

3) Choose Corrosion-Safe Hardware

Rain, salts, and tannic woods can chew uncoated steel. Pick stainless fasteners (304/305 inland, 316 near coasts) or true hot-dip galvanized bolts and washers. Use one system per joint so coatings match. Oversize washers spread load on slats and protect fibers around holes.

4) Measure Frames And Set The Span

Stand the iron sides upright and measure inside faces at the seat rails and back rails. Many two-seaters fall between 36 and 48 inches. Leave 1/8 inch clearance per side so slats drop in after finish.

5) Make A Cut List

Count the slats your frames were built for. Mill boards to a consistent thickness and rip to width. Crosscut to the span. Ease long edges with a 1/8-inch round-over for faster drying and comfort. Drill pilots to match your frame’s pattern; use a stop block for repeatable spacing.

6) Dry Fit, Seal, And Assemble

Assemble without finish to confirm alignment. Once spacing looks even, take it apart and seal every face, end, and hole. Penetrating stains move with the wood and refresh easily. Film-forming varnishes need stricter upkeep. Double-coat end grain. Reassemble from the center out and add a dot of exterior sealant in each pilot. Sit on the seat while tightening so the feet settle flat.

Comfort Tuning That Pays Off

Small tweaks change how a seat feels after ten minutes. If the frame allows, shim the back for a gentler lean. Keep the front edge rounded so it doesn’t press on tendons. Space slats with a 1/4-inch gap to drain rain.

Materials, Tools, And Costs

You can build with basic shop tools. A circular saw, drill/driver, countersink bit, and a sander cover most of it. Add a miter saw for speed and a round-over bit if you have a router.

Materials

• Cast-iron side frames (pair).
• Slats: cedar, white oak, teak, iroko, or treated pine.
• Fasteners: 1/4-in stainless carriage bolts, washers, lock washers, and nuts; or hot-dip galvanized equivalents.
• Exterior finish: penetrating deck stain or exterior oil; metal primer and enamel for the frames.
• Rubber or nylon feet pads; exterior sealant for pilot holes.

Tools

• Circular saw or table saw, miter saw, drill/driver.
• Countersink and 1/4-in drill bits, measuring tape, square, clamps.
• Random-orbit sander with 120/150/180 grits; router with 1/8-in round-over (optional).
• Wire brush, rust converter or primer, and paint for iron.

Joinery And Fastening Details

Most cast-iron ends use through-bolts. If yours have threaded inserts, chase threads with the right tap, then use machine screws with anti-seize. For through-bolts, drill clean pilots, add a slight countersink, and build each joint as: bolt head on the sitter’s side, then slat, then iron, then flat washer, lock washer, and nut.

Keeping Rust In Check

Moisture and the acids in some timbers speed rust. Stainless fasteners resist staining around oak and cedar. If you choose galvanized hardware, go with true hot-dip. Keep dissimilar metals out of the same joint. Touch up scratches in the iron paint when they appear.

Finishing For Weather, Not Just Color

Sun and rain beat up coatings. Penetrating stains protect without forming a brittle skin, so touch-ups are fast. On dense hardwoods like teak, a thin exterior oil refreshed once or twice a year keeps the golden tone; left bare, teak turns silver and still holds up. If you want paint, prime the wood and use a quality exterior topcoat. The U.S. Forest Products Laboratory details exterior stains and how they weather.

Finish Type	Best Use	Upkeep
Penetrating Deck Stain	Most softwoods and open-grained hardwoods	Re-coat every 1–3 years.
Exterior Oil	Teak, iroko, dense hardwoods	Wipe on 1–2×/year.
Paint (Primer + Topcoat)	Uniform color and UV shield	Prep heavy; touch up scrapes.
Clear Varnish/Spar	Gloss under cover	Regular sanding and recoats.

Step-By-Step Build Walkthrough

Layout And Cutting

Square one end of each board. Rip to width, then crosscut to final span. Pair pieces so grain looks consistent across the seat. Label the underside so assembly stays in order.

Drilling And Spacing

Clamp two slats together, mark hole centers from your frame, and drill pilots. Use that pair as a template. For spacing, make a 1/4-inch plywood shim and set it between slats as you bolt them down.

Seal, Dry, Assemble

Brush finish into end grain first, then coat faces. Let the first coat cure, then bolt the seat slats in, followed by the back. Check racking by measuring diagonals and nudge until they match.

Troubleshooting Quick Fixes

Slats Don’t Sit Flush Against The Iron

Castings aren’t always square. Add thin nylon spacers at bolt points or relieve the back of the slat with a shallow recess.

Finish Peels Early

That’s a film on top, not a penetrating stain. Strip loose areas, sand dull, and switch to a product you can refresh fast.

Orange Streaks Around Fasteners

That’s corrosion. Swap to stainless or true hot-dip galvanized hardware and clean stains with oxalic-acid wood cleaner.

Example Cut List For A Two-Seater

• Seat slats: 7 pieces @ 1 x 3 x span
• Back slats: 5 pieces @ 1 x 3 x span
• Arm infill (if your frame needs it): 2 pieces @ 3/4 x 2 x 8 in
• Carriage bolts: 1/4 x length for slat + iron + washers (often 1 3/4–2 1/2 in)
• Washers, lock washers, nuts, and optional acorn caps

Care Schedule

Spring: wash with a mild deck cleaner, rinse, and dry. Re-snug hardware. Mid-season: wipe on a thin refresher coat if the surface looks dull. Fall: touch up metal paint on scuffed feet. In winter, a breathable cover keeps standing water off.

Links to dig deeper: the AWPA’s Use Category System explains treatment levels for outdoor lumber, and the U.S. Forest Products Laboratory details exterior stains and how they weather. Both help you pick materials and finishes that last.