Garden Projects · 8 min read · Intermediate

How to Set Fence Posts: Holes, Concrete & Alignment

Plan post positions, hole depth, alignment and post-fixing concrete without assuming one universal depth or bags-per-post rule.

Key points & steps

Confirm the fence line, ownership/boundary position and panel or bay width before digging. Small spacing errors accumulate over a long run.
Check for buried services before excavating post holes. Do not assume a garden boundary is clear of electricity, water, drainage or communications services.
Choose post length and embedment for the fence height, exposure, soil and post system. Taller fences and windy/exposed sites need more resistance than a short sheltered panel.
Dig each hole wide enough for the selected post-fixing system and deep enough to provide stable embedment. Follow the post or concrete manufacturer’s guidance rather than relying on a single internet ratio.
Place the post plumb in both directions and brace it securely before adding concrete or proprietary post mix.
Use the fixing product at the stated water ratio/application method and keep the post aligned while it sets.
Shape or finish the top of traditional concrete around the post so water does not collect against timber where appropriate.
Allow sufficient cure/set time before attaching heavy panels or putting the post under wind load.
Recheck line, height and centres as you progress so one badly positioned post does not force every subsequent panel out of alignment.

The number of post-mix bags depends on the actual hole volume and product yield, not merely the fence height.
Very soft ground, retaining conditions, high wind exposure or unusual fencing systems may need engineered or manufacturer-specific foundations.
Concrete posts and slotted systems can have different hole and installation requirements from timber posts.