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How to make a mortar bed for a bath

Overview

You can keep a bath from moving around inside its frame by laying a mortar bed. We’ll teach you how to set the bath firmly into the mortar. You will also learn how to mix the mortar properly and build a barrier to hold it in place while it dries.

Steps

1Install fibre cement lining for the mortar bed

Measure the internal dimensions of your bath frame. Use a fibro cement cutter to cut lengths of fibre cement sheeting to fit. The sheeting will act as internal walls for the cradle and hold the mortar in place. They should be about 50mm higher than the bottom of the bath.
Person installing fibre cement lining.

2Mix the mortar for the bed for your bath

Use a shovel to mix up the mortar in your wheelbarrow. The mix ratio is four parts sand to one part cement. The mortar will be used to form a mound under the bath, so add your water in stages to make sure it doesn't get too runny.  Check out our How to mix mortar video for tips on the best way to do this.
Wheelbarrow full of mortar mixture and a spade.

3Make the mortar bed for the bath

Shovel the mortar into the bath frame, filling the space about 50mm higher than where the bottom of the bath will rest. Keep a clear space where the drain will be plumbed for the bath. To make this job a bit easier, you can temporarily take out one of the fibre cement sheets. 
Person shovelling mortar into bath frame.

4Place the bath in the mortar bed

Get someone to help you lift the bath into the cradle. Then make sure it rests on the frame and sits snugly in the mortar bed. Now fill the bath with something heavy to weigh it down. In this case, because our bath isn't plumbed, we've used bags of brickies sand. Once the bath is firmly in place, finish the job by using your hands to mould the mortar around the base of the bath and leave it to set for 24 hours.
Two people placing a bath into the timber bath frame they just made.
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.