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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
Health & Safety

Please make sure you use all equipment appropriately and safely when following the advice in these D.I.Y. videos. You need to be familiar with how to use equipment safely and follow the instructions that came with the equipment. If you are unsure, you may feel it is safest to consult an expert, such as the manufacturer or an expert Bunnings Team Member.

Grave health hazards are linked to asbestos, which may be in homes built up to 1990. Health hazards may result from exposure to lead-based paints in older materials and copper chromium arsenic (CCA) treated timber. 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.