🖼️
The project:
In December 2025, after taking handover of my newly built home, I designed and constructed a custom letterbox to complement its modern industrial aesthetic. The design needed to be lockable, weatherproof, suitable for A4 mail, and incorporate a mowing strip for easy maintenance. Using leftover and sample bricks from the house build, I created a rendered brick pillar with recessed street numbers, set on a concrete slab foundation and finished with a powder-coated metal mailbox. By sanding back the render and applying a wet-look sealer, I achieved a raw industrial finish. The project enhanced my home's street appeal and helped me connect with my new neighbours.
- Materials:
- Untreated framing pine (for framework)
- Hardwood Stakes
- Bastion Quik Set Concrete
- Silicone sealant
- Sand
- Bastion Cement
- Selley's Liquid Nails
- Printed numbers (free download off internet) Spruce Crafts number stencils
- Render
- Dulux Concrete Design Effect Paint
- Wet-Look Sealer
- Accent plant of your choice. Wheelbarrow, spade, box cutter, rubber mallet, pencil, empty ice-cream container or similar (brick sized), trowel, float, assorted screws, kitchen oil, spirit level, kitchen sponge, face mask.
- Tools:
- Cordless drill and driver
- Chisel
- Spirit level
- Detail sander
- Paintbrush
- Sandleford Wall Mount Letterbox Napoli
- 6.5mm masonry drill bit
- Step 1:
Site Prep
Scrape the site to remove grass and big clumps of clay. Make it roughly level to the eye.( In my case I also installed a retaining wall behind the site as it sloped both side-to-side and downhill as well).
- Step 2:
Concrete Slab
Construct the framework for the concrete slab using timber cut to the lengths specified in the sketch. I used 90 X 35mm untreated framing pine as a readily-available and cheap choice. Use wooden pegs (Lattice Makers Hardwood stakes) to position framework or drive screws from the outside of the frame in (so that they can be removed after the slab is cured). Because my block is on a slope, my slab needed to be thicker on the downhill aspect compared with the uphill aspect in order to create a level base. Confirm it is level with a spirit level. I made the slab nice and thick at 10cm and set the upper edge about 1cm lower than the ideal grass height so that the front of the slab could double as a mowing strip for maintenance of the nature strip (I don’t want to get out the edge trimmer if I can avoid it and I don’t want to risk the edge trimmer damaging the render on the brick pillar).
Pour the slab. I used Bastion QuikSet Concrete and Bastion Cement which I mixed in a wheelbarrow with a spade and smoothed off the top with an old float that I had in the garage.
After 48 hours I removed the formwork and then left the slab to further cure for another week to achieve maximum strength.
- Step 3:
Make your house-number brick
Find a box or an ice-cream container roughly the size of a brick, lightly lubricate it with ordinary kitchen oil (I used spray canola oil) and fill it with white silicone (I used Parfix Kitchen and Bathroom white sealant as it was the cheapest) to a depth of about 4cm. Smooth off the surface using a trowel dipped in water (to make it non-stick).
Once set, turn your silicone block out onto a flat surface. Go online and find a free downloadable number template (like the one provided in the materials list), save it and resize as required, then print. Lay this over your silicone block and trace it onto the block with a sharp pencil. Use a box cutter to cut out the numbers (or even letters if you want to spell out your house number instead).
Frame up a ‘one brick size’ formwork (230 x 110 x76mm). You can re- use the timber from the slab framework and cut it shorter and you can use the same screws and stakes again.
Mix up cement with water, fill the formwork. Take the numbers and press them down into the cement so that the top of the numbers sit level with the cement. Smooth over the top. Leave to cure. Once set, you can release the formwork and turn the flexible numbers out of the brick.
- Step 4:
Masonry Pillar
I used Selley’s liquid nails to bond the first row of 4 bricks to the exact middle of the slab and used a mix of cement and sand as mortar between the bricks. This left a good 7cm perimeter around the base of the pillar. Then I laid another 7 courses of bricks atop of this. The very last brick I laid was the one that I made myself with the house number recessed into it. I did one course at a time over several days so that I could take my time ensuring each course was level (use spirit level) and that the pillar front, back and sides were all flush as I wanted my pillar to be straight and neat. I used a rubber mallet to tap the brick into position and a trowel to apply the mortar. Every second course I needed to split two of the bricks, which I did easily using a hammer and brick chisel (Craftright Cold Chisel 2 piece set).
- Step 5:
Render the masonry pillar
Mix up the Dunlop Multipurpose Acrylic Render and liberally apply using a trowel. Take care to avoid blocking out the numbers with render and try and keep the render as even as possible with sharp edges. Over-render rather than under-render as you can always cut it back. Do a first-pass base coat, let it dry and then go back and add to this once dry. I used a wet finger to smooth the render flush where it met the edges of the number so that it looked tidy.
Use Ozito 200W Detail Sander to sand back render- ensure edges are sharp and surfaces are flush and even. Make sure you use a mask and prepare to get COVERED in dust! Also, leave this until later in the day as neighbours do not like getting woken up by the sound of sanding.
Apply final wash-coat of render. Just add a bit more water to the render and mix it in so it is thinner. You can use a kitchen sponge to apply and smooth this rather than a trowel. This also gives a nice texture to the finish.
Allow to dry. Hint: render takes a long time to fully cure and needs to be kept moist so that it doesn’t crack while it sets. I left mine for two weeks before painting and wet it down with the hose twice per day during this time.
- Step 6:
Finishing Touches
Paint it- Hose down the pillar to remove dust. Allow to air dry and then paint using Dulux Concrete Design Effect Paint and a Paint Partner 25mm paintbrush.
Install letterbox- I purchased the Sandleford Napoli Wall Mount Letterbox and installed it on my rendered masonry pillar using wall plugs and screws included in the pack. Hint: ensure the letterbox is level horizontally and vertically ( I used the Craftright magnetic spirit level which was great as it solidly attached itself to the letterbox and freed up my hands) and then mark drill holes with a pencil first. I used my Ozito PXC 18V cordless drill and driver set with a Kango 6.5mm sharp masonry bit which made it easy.
Sealer coat- Apply clear sealant to the pillar. I used Crommelin Wet-Look Sealer applied with the same paintbrush which I had used for the paint.
Lastly, go to Bunnings and pick out a nice evergreen shrub which is tolerant of poor soil, drought-hardy and has a low bushy profile. I used Westringea Low Horizon and planted it next to the letterbox as a soft accent. A clump of nice green strappy grass or Dianella would look great too.
