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Stumps fixed into the backyard.

Overview

The key to a durable and long-lasting deck lies in the care and attention given to assembling its substructure. Here is everything you need to know about installing stumps.

Safety tip: Always wear the appropriate safety equipment (safety glasses, ear muffs, gloves and a mask, for example) and always follow the instructions for the product or equipment.

Steps

1Determine the height

First, check your height to ensure you have enough clearance between the ground and your bearer. If you don’t have enough clearance, you may need to dig out some soil. A good shovel, pick and wheelbarrow will come in handy here.

Green Bunnings hammer
Note: Clearance heights vary on location, so it’s important to check local guidelines before beginning construction.
Measuring stump height using line laser and measuring tape.

2Measure and mark where the stumps go

Mark out where the stumps need to go. To determine the stump and bearer positions, always refer to timber-stand tables. If you’re building a deck on top of a concrete slab, use adjustable decking feet (i.e. builders feet) instead of stumps.

Man making marking where stump will go. 

3Dig the holes

Once you’ve marked out where the stumps need to go, you’re ready to dig holes for your stumps. Make sure the depth of your hole is founded at least 100mm into stiff clay. A good rule of thumb is that holes should be around 300 x 300 x 600mms deep; however, depths will vary depending on your location.

Man digging hole with shovel. 

4Apply bitumen paint

Before placing the stumps into the holes, apply a coat of bitumen paint to ensure the timber doesn’t rot. Allow to dry.

Man applying paint to stump with paint brush.

5Mix concrete

While the paint is drying, mix the concrete. You’ll need enough to fill each hole at least halfway. You’ll want at least a minimum of 150mm of concrete beneath your stump for support.

Man pouring concrete into the hole.

6Place stumps into the holes

Fill each hole halfway with concrete and place your stumps into the holes in-line with your string line. Check your stumps are straight using a level. Replace the soil in each hole and leave to set overnight.

Once the concrete is dry, mark the stumps off and cut them to your desired height.

Man placing stump in the hole.

7Are you ready for the next step?

Once your stumps are completed, it's time to get started on installing the bearers, the fourth step in our seven-part series on How to Build a Deck.

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More D.I.Y. Advice

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.