Cork Blocks and Bricks: Why Build With It (Pros and Cons)
Are you tired of building with the same old materials? Do you want a unique, eco-friendly alternative that’s durable and affordable?
If so, cork blocks and bricks might be the best option. Cork blocks and bricks are becoming popular among builders because they’re unique and promote sustainable living.
But before jumping on the cork bandwagon, weighing its pros and cons is essential. This way, you’ll know if cork blocks and bricks are the right material for your project. It’s the best way to avoid regrets that come with making the wrong decision.
In this article, I’ll discuss cork blocks and bricks, their manufacture, and their best uses. I’ll also discuss their pros and cons to help you understand the ins and outs.
Let’s dive right in!
What Are Cork Blocks and Bricks?
Cork blocks and bricks are building materials manufactured from cork granules. These materials are designed to be used just like regular concrete building blocks/bricks but with the added benefit of being more sustainable.
Cork blocks and bricks come in different shapes and colors.
The table below shows the standard sizes of cork bricks:
| Stick Bricks | Grand Bricks |
| 450 x 70 x 6mm (17.72″ x 2.76″ x 0.25″) | 300 x 200 x 4mm (12” x 8” x 2/16”) |
| 300 x 70 x 8mm (11.82″ x 2.76″ x 0.32″) | 200 x 200 x 7mm (8” x 8” x 5/16”) |
| 150 x 70 x 11mm ( 5.91″ x 2.76″ x 0.43″) | 200 x 100 x 11mm (8” x 4” x 7/16”) |
Table 1: Common sizes of cork bricks
The Making of Cork Blocks and Bricks
Building materials must be highly durable, strong enough to sustain the building’s weight, and highly resistant to the elements. Achieving these qualities in cork blocks and bricks requires a unique manufacturing process that involves the following procedure.
- Harvesting cork bark: Cork is harvested sustainably from the bark of cork oak trees. Horizontal and vertical cuts are made into the tree’s trunk to remove the bark. These cuts are done carefully not to destroy the trunk’s living portion. Once removed, the cork planks are stacked outside to cure for several weeks to six months.
- Plank treatment: The cork planks are treated with water and heat to remove water-soluble components like tannin and dirt. The treatment also serves to soften the material.
- Breaking the planks into granules: The cork planks are passed through a machine that breaks them into smaller pieces. These pieces are washed, dried, and then passed through grinders that chop them into cork granules.
- Mixing the granules with a binder: The granules are ground up and mixed with a binder (polyurethane, melamine, or rubber) to make a homogenous material that holds together during compression. The mixture is then shaped into the desired size and allowed to dry.
- Compression: The dried cork mixture is placed into a mold and compressed using heat and pressure at 500°F (260°C). The heat softens the cork and allows it to conform to the shape of the mold, while the pressure helps bind the cork together into a solid block or brick.
- Finishing the blocks/bricks: Once the bricks are compressed, they are typically sanded and trimmed for a smooth, uniform surface. They can then be sealed or treated with a finish to protect them from moisture and wear.
Best Uses for Cork Blocks and Bricks
Cork blocks and bricks are ideal for the following:
Roofing
Cork is highly impermeable and suitable for roofing.
However, since cork blocks and bricks are made from expanded cork granules, they require more modification to be ideal for roofing.
It’s worth mentioning that the standard-density expanded cork blocks used in construction may have fissures and voids between the granules, approximately 16% in 130 kg/m3 of cork. If not addressed, these fissures can give a route for water and air seepage through the roof.
Therefore, when used for roofing, cork blocks and bricks must incorporate the following:
- Air pressure equalization slots: For balancing air pressure within the joints. This ensures that rainwater is not externally sucked into the joints.
- An airtight tape across the joints: Eliminates the possibility of wind pressure differentials sucking rainwater into the house.
- Drainage Channels: Drain water from the joints.
Flooring
Standard-density expanded cork blocks and bricks are ideal for flooring when used with a cement-based adhesive. The material is waterproof, shock absorbent, and provides excellent thermal insulation.
It’s also highly durable and can last over 40 years with proper maintenance.
Walls
Are cork bricks suitable as the primary wall structure for a building?
The answer is yes.
In 2018, Studio Bark built a solid cork building with cork blocks from Cork Link. The walls were made with high-density expanded cork blocks and fitted with support beams.
Since cork walls are naturally insulated, they keep the building warm in winter and cool in the summer.
The Pros of Cork Blocks and Bricks
Excellent Strength and Durability
Cork bricks are highly strong and durable, thanks to cork’s excellent tensile and axial properties and high water resistance.
Cork has a Young’s modulus ranging from 26.1 to 30.8 Mpa and structure stress strains between 5.5% and 7.1%. These qualities make cork bricks highly strong to resist structural pressure and wear.
On the other hand, the material’s excellent water resistance makes it possible to withstand high moisture conditions. Therefore, it’s not susceptible to rot, mold and mildew.
Excellent Thermal Insulation
Thermal insulation is crucial in places with regular temperature fluctuations.
Cork’s honeycomb structure creates millions of tiny air-filled cells. The air in these cells blocks most heat from getting through the cork’s layer, making it a good insulator.
Cork’s poor thermal conductivity, between 0.036-0.38 W/mk, increases its ability to resist heat flow, enhancing the material’s insulating capacity.
Natural, Eco-Friendly Material
Cork is a 100% natural material made from the bark of cork oak trees. This means it’s fully biodegradable and recyclable.
Cork’s high sustainability, stemming from its harvesting, processing, and use, makes cork bricks ideal for sustainable construction and green building projects.
Lightweight Yet Rigid
Over 50% of cork’s volume comprises air enclosed in the micro-cells, which is responsible for the material’s lightweight nature.
Consequently, cork blocks and bricks are easy to carry and install in construction projects, reducing installation labor costs.
Excellent Acoustics
Cork blocks and bricks have excellent acoustics due to the material’s high noise reduction coefficient (NRC) and air-filled cells.
With an NRC of 0.7, cork absorbs 70% of sound waves that hit it, reflecting only 30%. This makes cork-built rooms quieter and more comfortable.
Moreover, since air is a poor conductor of sound, it blocks sound within the bricks’ layers, prevents it from passing through the wall, or attenuates it significantly.
The Cons of Cork Blocks and Bricks
Costly
Cork blocks are more expensive than traditional building materials like concrete and bricks since they require specialized processing and curing.
Moreover, since cork is harvested periodically, its availability and cost vary depending on the seasons.
Susceptible to Fissures
Cork blocks have many fissures, especially the low and standard-density expanded options. These options may be more porous due to the air bubbles in the micro-cells.
Unfortunately, fissures can weaken structural integrity if exposed to extreme pressure.
They Require Moisture Sealing
Although cork is perceived as a waterproof material, it can absorb moisture over time. Therefore, roofing cork blocks must be sealed with a wax or polyurethane-based sealant to enhance their waterproofing properties.
Frequent sealing may be required every five to seven years to enhance longevity.
Limited Availability
The Mediterranean region is the largest cork producer globally, accounting for 84.9%. This means that cork blocks and bricks availability is limited to countries within these regions.
For other countries, importation of cork bricks is necessary. Consequently, the cost of transport and shipping add to the material’s overall price.
So, Why Build With Cork Blocks and Bricks?
Cork blocks and bricks bring lots of advantages to the table. They are strong, lightweight, insulating, eco-friendly, and have excellent acoustic properties. These qualities make them ideal for many construction projects.
That said, cork blocks are expensive, have limited availability, and are susceptible to fissures. Therefore, you must consider these drawbacks before incorporating these materials into your project.
There are many other sustainable building products besides cork bricks and blocks, such as compressed earth blocks. But are they worth it? Check out this article about compressed earth blocks to find out.
