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How to build a rendered block bench

By Bunnings magazine /

Block bench with timber slats, hat, rug and plant

Overview

Turn a handful of humble materials into a custom timber and concrete-look seat. Soften this sleek, yet heavy-duty bench with outdoor cushions, potted plants and a jute rug for an attractive and comfortable reading space. But first, here’s how we built the bench.

Safety tip: The finished pillars are heavy. It’s best to build the bench on site over a stable foundation.

Steps

1Prepare the timber slats

Smooth with a random orbital sander using a 120-grit abrasive disc to remove splinters and round over the edges, finishing with 180-grit. Apply two coats of outdoor furniture oil, wiping away any excess with a cloth and leaving to dry after each coat.
A person sprays furniture oil onto timber slats

2Make two pillars with the blocks

Set out the first rows of two blocks with holes facing up, 1200mm apart (measured from the inside). Use a builder’s square to keep them perpendicular to the wall while applying landscape adhesive underneath, between and along the top to secure the second row.
Landscape adhesive applied to besser blocks

3Adhere the slats to the blocks

Apply adhesive around the top to position the third row of blocks with the holes facing sideways. Apply adhesive in the holes and centre the slats between them, pushing down to embed and leave to dry.

Green Bunnings hammer
Tip: The adhesive dries fast and saves having to mix up concrete.
Timber slats adhered to besser blocks with landscape adhesive

4Fill block holes with expanding filler 

Wrap tape around the base of the pillars to protect from spills. Wear disposable gloves and follow the manufacturer’s instructions to apply a row of expanding filler in each hole. Leave it for 15 minutes to expand, apply another layer and repeat to fill completely.
Expanding filler in besser blocks

5Remove excess filler and smooth the surface

When the expanding foam has cured hard, use a mini-hacksaw blade to trim it level with the blocks, smoothing the surface using a sander with 120-grit abrasive disc. Sweep up the foam pieces and brush over the pillars to remove dust. Tape around the slats, against the pillars, to protect them from render.
Mini hacksaw used to remove excess expanding foam

6Mix the render and apply to blocks

Half-fill a bucket with render, gradually adding water and mixing to a toothpaste-type consistency using a 75mm scraper. Spray the pillars with water, then apply an even 5mm-thick coat of render, using the trowel to wipe it smooth.

Green Bunnings hammer
Tip: Use two buckets of render per pillar, mixing as needed.
A person coating concrete blocks with render

7Smooth render over the slat corners

Use a 75mm scraper to smooth over the corners and down the edges. Use a 38mm scraper to apply render neatly around and between the slats, feathering it into the larger areas. To render underneath the slats, lie on a drop sheet and use the scrapers to apply a thin layer.
A person using a scraper to smooth out render

8Sponge over the render

Using a damp sponge, smooth over the render, regularly rinsing it clean in a bucket of water, while neatening along the edges and around corners, touching up underneath and around the slats.
A person rubbing a damp sponge over a rendered block

9Finish the blocks with concrete sealer

Remove the tape and leave the render to dry thoroughly (at least two days). It lightens as it dries – wait for the entire surface to appear uniform. Brush to remove loose particles, then finish with clear concrete sealer using a mini-microfibre roller.

*Timbers vary by state and territory; contact your local store for further information.

Green Bunnings hammer
Tip: Alternatively, seal the pillars with two coats of quick-dry paving paint.
A person peels painter’s tape off timber slats]

10More D.I.Y. bench projects

If you’re in the mood to take on another weekend project, check out our on-trend woven bench seat project.
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.