Before you start anything, go check out this article first: https://www.mgo-construction.fr/meuble-salle-bain-siporex. It shows you what a Siporex cabinet looks like, how it’s used in real bathrooms, and gives a solid overview. Read it, then come back here for the hands-on part.

Why choose Siporex

Siporex is cellular concrete. It’s lightweight, easy to cut, cheap, and once it’s set in place, it’s solid. It handles moisture without a problem, doesn’t rot, and gives you a clean base to tile, paint, or coat with waxed concrete.

You can shape it exactly how you want. That means custom shelves, niches, cutouts for plumbing, and the exact height you need. It’s perfect for DIYers who want a tailored, durable piece of furniture.

Planning your layout

Start with a sketch. Measure your space properly, including wall clearances, pipes, drain lines, and the height of your sink if you’re integrating one. Know exactly how deep and high your unit should be.

Figure out where you want openings, shelves, supports, or decorative elements. This saves you a ton of trouble during the build.

What you’ll need

Basic list:

• Siporex blocks (typically 5 to 10 cm thick for furniture)
• Special glue for cellular concrete (powder or ready-mixed)
• A handsaw or wood saw (yep, that works)
• Spirit level, tape measure, pencil
• Bucket, trowel, sponge
• Reinforcement mesh if needed (for large surfaces)
• Finishing materials (tile, plaster, paint, etc.)

Pro tip: work on a flat surface. If your floor is uneven, you’ll regret it later.

Cutting and assembling

Mark your blocks clearly before cutting. Siporex cuts like dense foam with a handsaw, just go slow and steady. Use a straight edge if needed.

Start building from the ground up. Apply the adhesive with a notched trowel like you would with tile glue. Press the blocks together gently but firmly. Check with a level every time. Don’t rush it.

Let each layer set a bit before stacking more, especially if you’re building tall sections or adding load-bearing parts.

Creating openings and shelves

You can easily notch out parts of the blocks to make niches or openings. Just cut and chisel carefully. For horizontal shelves, support is key. Either use L-brackets, reinforcement mesh, or blocks cut to act as pillars underneath.

If you’re placing a heavy sink on top, reinforce the structure under the basin. Siporex is strong, but smart load distribution is smarter.

Smoothing and finishing

Once the structure is done and dry, it’s time to smooth it. Use a float or a sanding block to remove glue lumps or surface bumps.

Then apply a waterproof finish. Here are your options:

• Tile it with waterproof adhesive and grout
• Apply a concrete coating or waxed concrete for a seamless look
• Paint it with moisture-resistant paint (not ideal near running water)

Don’t skip this step. Even though Siporex is moisture-tolerant, your finish protects it and gives it the final look.

Final tips

Let everything dry fully before installing your sink or loading up the shelves. If you’re tiling, wait at least 24 hours after the last block was glued. Be patient. It pays off.

Keep joints clean as you go. Wiping excess glue with a sponge right after application saves time later.

And most of all, take your time measuring and leveling. Bad cuts and uneven surfaces create ugly problems once the cabinet is finished.