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What Size Hole Do You Drill for Balusters?
For a 1/2″ square iron baluster, drill a 3/4″ hole. The rule: a square baluster needs a hole wider than its corner-to-corner width so it can turn, and a round baluster needs a hole about 1/8″ bigger than the bar. Drill 1/4″ to 1/2″ deep into the tread and 1″ to 1-1/2″ up into the handrail. A base shoe covers the extra room around the bar.
Drill Bit Size Chart for Iron Balusters
| Baluster size | Drill bit (paddle bit) |
|---|---|
| 1/2″ square | 3/4″ |
| 1/2″ round | 5/8″ |
| 9/16″ square | 7/8″ |
| 9/16″ round | 11/16″ |
| 5/8″ square | 1″ |
| 5/8″ round | 3/4″ |
| 3/4″ square (MEGA) | 1-1/8″ |
Not sure what size your balusters are? Measure the bar near the bottom, where the shoe sits. Most of our iron balusters are 1/2″ square. Tuscan Hammered, Gothic Hammered and the Round series are 9/16″, Wentworth, Designer Square, Designer Round and Monte Carlo are 5/8″, and MEGA balusters are 3/4″ square.
Why Square Balusters Need a Bigger Hole
A square bar is wider from corner to corner than it is across a flat side. A 1/2″ square baluster measures about 0.71″ corner to corner, so it won’t turn in a 5/8″ hole. You need room to rotate each baluster until it lines up with the others, which is why a 1/2″ square bar takes a 3/4″ bit.
Don’t want to use shoes? Use a mortising bit to cut a square hole that fits the bar exactly, with no gap to hide.
How Deep to Drill
| Where | Hole depth |
|---|---|
| Tread or floor | 1/4″ to 1/2″ |
| Handrail | 1″ to 1-1/2″ |
The handrail hole is deeper on purpose. Cut each baluster 3/4″ longer than the space between the tread and the handrail, push it up into the rail, then drop it down into the tread hole.
Wood Balusters
Wood balusters with a round pin on the end go into a hole the same size as the pin, so measure the pin and match your bit to it. Square-top wood balusters usually go into a plowed handrail with fillet strips instead of a drilled hole.
Replacing Wood Balusters With Iron
Your old holes probably won’t match. If they’re too big, a base shoe will usually cover the gap. If they’re too small, drill them out with the right bit from the chart. Either way, set the balusters with EPC-410 epoxy.
Ready to Drill?
For the step-by-step, with marking, keeping the drill plumb and a video, see how to drill holes for iron balusters. Then follow how to install iron balusters.
Baluster Hole Size FAQ
What size hole do I drill for a 1/2 inch square baluster?
A 3/4″ hole. A 1/2″ square bar is about 0.71″ corner to corner, so it needs a 3/4″ hole to turn and line up.
What size hole for a 1/2 inch round baluster?
A 5/8″ hole, about 1/8″ bigger than the bar.
What size hole for 9/16 balusters?
7/8″ for 9/16″ square balusters and 11/16″ for 9/16″ round balusters.
How deep should baluster holes be?
1/4″ to 1/2″ into the tread or floor, and 1″ to 1-1/2″ up into the handrail.
Should I drill baluster holes at an angle?
No. Drill straight up and down (plumb) in both the treads and the handrail, even though the handrail is on an angle. Otherwise the balusters will lean.
