Mount Deck Rail Posts
Notching posts over the band board, staging the carriage bolts so plumb survives tightening, and blocking so the rail takes a real lateral load.
Notch a Tall Post to Carry a Drop Beam
Lay out the beam's top and bottom on the post face, cut both side faces to depth, then make a series of close relief cuts between them — the waste knocks out in chunks and a reciprocating saw cleans up the back of the notch. The beam ends up bearing in a C-shaped seat cut from the post.
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The Problem
When a drop beam runs through a post that continues up past it — a 20-footer carrying a roof or rail above the beam line — a seat cut into the top of the post isn't available. The beam needs a C-shaped seat cut out of the post's side, at exact height, deep enough for full bearing, without cutting the post in half.
The Technique
The creator's worked example: beam top at 95", built from 2x10s that actually measure 9-3/8".
- Mark the beam's top elevation on the post face — here, 95".
- Measure down the actual height of your beam stock — 9-3/8" for a 2x10 — and mark again. The two lines bracket where the beam will sit.
- Set your circular saw to the notch depth and cut along both lines.
- Make a series of relief cuts between them, and cluster several close together near one end — those tight pieces knock out first and open room for the saw.
- Roll the post to one side face and connect the cuts to depth; flip and repeat from the other side.
- Knock out the waste — most of the relief-cut blocks pop free — then run a reciprocating saw in behind what's left to take the back of the notch down flat.
Safety note: A notch this size
removes real cross-section from a structural post. Notch depth and the
post-to-beam fastening are code and engineering questions — match your
plans or your local code's post-notching limits, and through-bolt the beam
per your jurisdiction's deck details rather than relying on the seat
alone.
Electrical, plumbing, and structural work may be regulated where you live — check local code before you start, and note that a permit may be required. More in our disclaimer.
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