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How to level a subfloor

A person pointing to a gap between a floor joist and a straight edge place across it

Overview

The best way to ensure your floor is flat is to have a level subfloor. We’ll show you how to level a subfloor yourself using a straight edge and a plane. You’ll learn how to find the high spots on your joists and the best way to plane your joists down.

Steps

1Find the high spots on the joists in your subfloor

Run your straight edge across several joists at once. If the straight edge seesaws on any of the joists instead of sitting flat, then that joist is sitting higher than the others. Move the straight edge up and down the high joist to see where the high section starts and finishes. Mark the high area up with a pencil. Repeat across the floor to find all the high spots.
A person pointing to a gap between a floor joist and a straight edge place across it

2Plane the high spots on the joists in your subfloor

Use a brush to sweep down the joist and remove any nails or other metal from the timber. Use your plane to trim the high section of the joist down. Only take off 1-2mm at a time. Keep checking the level with your straight edge as you go. Once the straight edge sits flat across all the joists, your job is done.
Bunnings team member planing a joist

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Health & Safety

Asbestos, lead-based paints and copper chromium arsenic (CCA) treated timber are health hazards you need to look out for when renovating older homes. These substances can easily be disturbed when renovating and exposure to them can cause a range of life-threatening diseases and conditions including cancer. For information on the dangers of asbestos, lead-based paint and CCA treated timber and tips for dealing with these materials contact your local council's Environmental Health Officer or visit our Health & Safety page.

When following our advice in our D.I.Y. videos, make sure you use all equipment, including PPE, safely by following the manufacturer’s instructions. Check that the equipment is suitable for the task and that PPE fits properly. If you are unsure, hire an expert to do the job or talk to a Bunnings Team Member.