Creating with Recycled Plastic Bricks: My Practical Experience
Trust me, getting to say at a social gathering that you finally managed to contribute in a tangible way to saving this poor planet of ours is something you won’t forget. It really does make you proud.
Switching to sustainable building materials has been a game-changer in my construction projects and made me proud. After exploring options like Ferrock, I turned my attention to recycled plastic bricks. It’s a long story, but what matters is that I did it. Here’s a detailed account of how I incorporated them into my work, the challenges I faced, and tips for anyone looking to do the same.
Building with Recycled Plastic Bricks: What Actually Works
I’ve built with a lot of materials. Clay brick, concrete block, lightweight AAC, even a few Ferrock trials. Nothing confused the crew like the first pallet of recycled plastic bricks. “Plastic? In walls?” Fair question. But the waste stream is massive, and if you’re on sites long enough, you know how much ends up as landfill. I wanted to see if some of it could come back into the build.
How It Started
It began with a pile of rejected containers behind a recycler. A worker mentioned they sold ground plastic to a shop that presses it into blocks. A week later I had a sample—dense, slightly waxy, and it bounced when I dropped it. That bounce said “tough,” not “toy.”
Most of these bricks are made from HDPE—the same family you’ll see in jugs and cutting boards. If you need a quick primer on the material itself, here’s a clean overview: HDPE in construction.
Why Plastic Made Sense on Paper
My job sites throw off wrap, pipe offcuts, packaging—constant. Recycled plastic bricks offered three things worth testing: lower embodied energy, zero water absorption, and lighter handling. Some manufacturers blend in PP or fibers, sometimes sand, to tune stiffness. No firing, no kiln, lower carbon than clay.
But I didn’t buy them for the brochure. I bought them because I was tired of hairline cracks and damp lines telegraphing through traditional walls. Water wicks up clay like a straw. Plastic doesn’t wick anything. That alone deserved a field test. For broader context on trade-offs, see this scan of what actually works and fails: sustainable building materials: wins and misses.
The First Pallet
Source: small plant outside Toronto. Count: 420 bricks, roughly 10 × 5 × 4 in. Unit weight ~1.2 kg. Colors inconsistent (grey, green, the odd pink fleck), but dimensions were true and edges crisp. Freight was cheaper than clay because the shipment weighed less. Cut one in half—clean core, faint detergent smell, no voids.
Shop Tests (Week One)
Compression
Short stacks loaded with pavers until failure. I measured ~8–9 MPa before plastic deformation. Typical clay sits around 10–12 MPa, concrete block 12–15 MPa. Not the champ, but in the arena.
Water Soak
48-hour submersion test. Zero uptake, no swelling, no spalling. Compare that to clay’s 10–15% absorption. This was the first big “hmm.”
Impact & Handling
Drop tests from shoulder height: bounce, scuff, no chips. That resilience matters in transport and staging.
Cutting & Shaping
Dry diamond blade melted the edge; a heated wire cutter made perfect, crisp cuts with minimal smoke (ventilate). That single tool change sped everything up.
Adhesion
Standard mortar slid off the smooth faces. Solution: scuff the contact areas + add latex bonding agent to a polymer-modified mortar. After cure, bond strength was reliable.
Field Build: The Garden Shed
Prototype scale: 2.4 × 3.6 m shed behind a rental. Walls in plastic brick, light steel roof frame, metal cladding.
Foundation
100 mm concrete pad, key-notched perimeter. First course set on polymer-modified mortar with faces abraded. Wet the pad lightly before placing for better grab.
Wall Laying & Openings
Stacking was fast: no chipping, no dust, fewer breaks. Tapping a course produced a dull thud (plastic) instead of a ring (clay), which made the site quieter. Openings cut cleanly with the heated cutter; we added a light timber lintel where needed.
Roof & Uplift
Corrugated metal roof on light framing. Because the wall mass is low, I over-anchored the top plate and added a discrete tension-tie set at corners to handle wind uplift.
Problems We Hit (And Fixes)
1) Mortar Compatibility
Issue: Early joints debonded overnight.
Fix: 80-grit scuff on contact faces + 10% latex in polymer mortar. Full cure before load. Night-and-day difference.
2) Thermal Movement
Issue: Hairline gaps appeared on the sun-soaked south wall by late afternoon.
Fix: 3 mm vertical expansion joints every 1.2 m, filled with a UV-stable elastomeric sealant. No more ghost lines.
3) UV Surface Fade
Issue: Color dulled after 3 months of summer sun.
Fix: Roll-on acrylic UV topcoat; as a bonus, the slight texture boosted future coating adhesion.
4) Fasteners
Issue: Over-torqued screws strip quickly in plastic.
Fix: Pre-drill pilots, use stainless screws, set clutch low. For heavier fixings, install blocking or use through-bolts to a backing plate.
5) Sound
Issue: Bare plastic reflects sound; interior was echoey.
Fix: 12 mm plywood liner + mineral wool. Solid acoustic improvement.
Six Months, Then a Year: What Stuck
Ontario winter, summer storms—no leaks, no efflorescence, no frost lines, no pest damage. Temperature swings inside were milder than an equivalent timber shed because the envelope stayed dry and airtight. Maintenance = hose it twice a year. If you want a quick side-by-side of common materials (weight, absorption, compressive ranges), this short reference helps frame choices: every building material, at a glance.
The Numbers That Matter
| Metric | Recycled Plastic Brick | Clay Brick | Concrete Block |
|---|---|---|---|
| Unit weight | ~1.2 kg | ~2.7 kg | ~3.5 kg |
| Compression (MPa) | 8–9 | 10–12 | 12–15 |
| Water absorption | ~0% | 10–15% | 5–8% |
| Embodied energy (relative) | Low | High (kiln-fired) | High (cement) |
| Recyclability | Closed-loop potential | Difficult | Partial |
| Typical unit cost (CAD) | ≈ 1.25 | ≈ 0.80 | ≈ 1.10 |
Our shed used ~410 bricks. Materials ≈ $512, mortar/bonding ≈ $46, about 12 crew-hours for two people. Comparable clay job took ~16 hours; labor savings largely offset higher unit price.
What I’d Tell a Builder (Short List)
- Weight changes detailing. Anchor top plates and plan for uplift; don’t rely on wall mass.
- Don’t copy clay details. Treat this as its own system—joints, ties, coatings, fixings.
- Moisture is easy mode. No capillary rise, no salt bloom. That’s real money saved later.
- Mind acoustics. Add liners or absorbents for comfort.
- Aesthetics: pick a lane. Celebrate speckled color or coat it—no halfway.
Comparisons, Fast
| Material | Pros | Cons |
|---|---|---|
| Recycled Plastic Bricks | Light, waterproof, resilient, waste-reducing, easy shaping | Needs bond strategy; thermal movement; limited fire ratings |
| Clay Brick | Familiar, proven, strong | High energy to fire; absorbs water; efflorescence risk |
| Concrete Block | Cheap, strong, great mass | Heavy, higher CO₂, thermal bridging without breaks |
| Ferrock | Carbon-negative, very strong | Heavy; limited availability; cost variability |
| Timber Panels | Fast, renewable, easy to work | Moisture management is critical; fire detailing required |
Field Mistakes to Avoid
- Skipping expansion joints (you’ll chase cracks later).
- Using plain cement mortar (bond failure is guaranteed).
- Over-torquing screws (strip city—set the clutch low).
- Ignoring UV protection on exteriors (premature fade, chalking).
- Expecting color uniformity (batch variation is normal).
FAQ
How long do they last?
HDPE itself can run 50+ years if shielded from UV. With coatings and proper detailing, service life can rival light masonry envelopes.
Can they carry a roof?
Yes—light roofs and short spans with ring beams or lintels. Treat heavy loads with reinforced elements as you would with other lightweight systems.
What about fire?
HDPE softens before melting (~130 °C). Use non-combustible linings and comply with local fire ratings. Treat the wall as a non-structural skin where codes demand.
Do they off-gas?
Post-molding, the material is stable. Cutting produces a mild plastic odor—work with ventilation or outdoors.
Can I plaster over them?
Yes—use a bonding primer or mesh. Plain mortar on smooth plastic will fail.
Recyclable again?
Yes. Heat and remold. That closed-loop potential is a core advantage.
Would you use them again?
For sheds, small homes, classrooms, and flood-prone sites: yes. Dry, light, repairable, and honest about what they’re good at.
What I’d Do Differently Next Time
- Pre-set anchor bolts and layout the ring beam early.
- Test two UV coats side-by-side from day one.
- Plan interior acoustics before move-in (liner + insulation spec).
RECOMMENDED TOOL (after real-world testing)
FIELD PICK: Heated foam/plastic cutter — the single tool that made shaping fast and clean.
See the cutter on Amazon
MUST READ (kept on my desk)
Building Construction Illustrated — Francis D.K. Ching. Clear diagrams for details that actually get built. Great for students and site leads alike.
Get the book on Amazon
Disclosure: As an Amazon Associate I earn from qualifying purchases.
Keep Exploring
If you want a quick sweep of proven low-carbon options and where they fail in the field, this plain-spoken overview is a good next step: materials that deliver vs. hype. For a deeper dive into the base polymer you’ll actually be laying, skim this refresher on HDPE’s behavior in construction.