Cork Building Material Pros and Cons (What Is It Anyway)?

Cork—it’s a material that many of us have seen, felt, or even used. But do you know where it comes from and why so many builders are buzzing about it?

Gone are the days when cork was limited to pinboards or bottle stoppers – now, we have cork building material for construction.

Cork building material is a renewable and sustainable construction material made from the bark of the cork oak tree. Once the bark is removed, it’s granulated, ground, and combined with polyurethane as a binder. The mixture is exposed to steam and superheated at 600°F (315.56°C) for agglomeration.

In the rest of this article, I’ll discuss the pros and cons of cork building material. I’ll also discuss the best places to use cork in construction.

Let’s find out if this natural yet modern-day wonder suits your upcoming project.

Cork Building Material: The Basics

From cork wine stoppers and fishing tackle to roofing in China and Italy, the use of cork has a rich history dating back to 3,000 BCE.

The use of cork in construction became a reality in 1890 in Germany. A German company invented a method of incorporating cork particles with clay as a binder to make agglomerated cork sheets for insulation.

John Smith, an American, advanced the invention in 1891 by producing pure-cork agglomeration. His approach involved subjecting cork particles to heat and pressure without a binder.

Unbeknown to many, cork is a good material for protecting the environment; it’s highly sustainable and renewable.

Producing cork doesn’t involve environmental destruction. The bark of the cork oak tree (Quercus suber) is the only part used.

The top part of the bark (suberin) is harvested sustainably by stripping it off the tree’s trunk every 9-12 years. This way, the tree has sufficient time to grow its bark back before it’s re-harvested.

The use of cork in wall coverings, flooring, and insulation has been on an upwards trend. Besides the material’s green nature, Research Gate states that this projection is attributed to cork’s lightness, resilience, elasticity, and impermeability.

Finally, countries within the Mediterranean region, like Portugal and Spain, remain the highest producers of cork building material. This is because cork oak trees are native to this region.

The Pros of Cork Building Material

Cork building material has plenty of benefits, making it an excellent choice for construction projects. Here are some advantages:

Sustainable and Eco-Friendly

The construction industry accounts for 50% of climate change. This is because conventional building materials like concrete generate massive greenhouse gas (GHG) emissions accounting for 40% of global emissions.

We can address this menace by shifting to sustainable and eco-friendly materials like cork.

Unlike other construction materials, cork doesn’t involve the depletion of natural resources because it’s sourced sustainably.

What’s more, cork is a renewable and recyclable resource. After its extraction, the cork oak tree is given 9 to 12 years to regenerate its bark before re-harvesting.

Finally, cork is biodegradable. Therefore, when it comes to the end of its lifetime, it decomposes without releasing nasty toxins into the environment.

Excellent Thermal Insulation

Insulating our home is an excellent way to reduce our heating and cooling needs, thus lowering our energy bills.

Cork is an excellent insulator thanks to its poor thermal conductivity and high R-value per inch.

Cork’s poor thermal conductivity (0.036-0.38 W/mK) is attributed to the material’s composition with tiny air-filled cells.

Since air is a poor conductor of heat, it blocks the transfer of heat energy across the cork’s surface, thus providing exceptional thermal insulation.

Not only that, but the material also boasts high R-values between R-3.6 to R-4.2 per inch, depending on the density.

This high R-value is useful, especially during extreme temperature fluctuations, as the material keeps indoor temperatures constant. Consequently, you use less energy for heating and cooling.

This fact explains why cork is used in external thermal insulation composite systems (ETICSs).

Excellent Acoustic Insulation

You need sufficient acoustic insulation if you live in a noisier neighborhood or want to minimize indoor noise.

Cork makes an excellent acoustic insulator for homes and commercial buildings for two reasons:

• Structural composition: The material comprises air-filled cells that block and absorb sound waves that then cannot penetrate the house.
• Noise Reduction Coefficient (NRC): With a high NRC of 0.7, cork absorbs up to 70% of noise, making the indoor environment peaceful.

It’s worth mentioning that cork’s thickness is crucial in sound insulation. Aim for at least a 3-millimeter (0.12-inch) cork layer for the best results.

Highly Impermeable

We all want our houses to be well-sealed so as not to let in outside elements like moisture.

Cork is highly impermeable, thanks to its 100% natural composition with suberin.

Suberin is a highly impermeable substance between the mesophyll cells and bundle sheath.

This component stops the penetration of moisture from the environment, which explains why cork is suitable for wall coverings, flooring, and roofing.

It’s also worth mentioning that, unlike wood, cork building material doesn’t rot, helped by the polyurethane binder. Therefore, it offers excellent protection from moisture as well as fungal infestations.

Low Embodied Energy

Embodied energy is the energy needed to produce, transport, and install a building material.

Cork offers low embodied energy because it’s harvested from regenerative trees and requires minimal processing.

Moreover, cork is a lightweight material weighing between 10 and 15 pounds per cubic foot. Therefore, you don’t need heavy machinery that uses lots of energy to install it.

Finally, cork has an embodied carbon of almost zero. This means it doesn’t produce significant amounts of carbon during processing and installation compared to other materials like concrete. Thus, it’s an ideal choice if you’re looking to reduce your home’s carbon footprint.

The Cons of Cork Building Material

It would be remiss of me not to mention the cons of using cork as a building material. To help you in decision-making, here are the drawbacks of cork:

It’s Costly

I’ll be frank; cork is more expensive than other insulating materials like fiberglass and sheep’s wool insulation.

While cork costs between $3 and $10 per square foot depending on thickness, fiberglass and sheep’s wool insulation costs between $0.88 and $1.64, and $1.10 and $3.10 per square foot, respectively.

The high cost of cork is brought about by the fact that the material is harvested periodically. It also requires skilled laborers for sustainable harvesting.

Although the initial cost of cork is high, its long-term benefits, like energy conservation, are worth the investment.

It’s Prone to Damage

Cork is highly susceptible to damage due to its soft nature.

Using cork flooring requires a great deal of maintenance. The material’s softness makes it unsuitable for heavy furniture.

Moreover, sharp objects like high heels can leave marks on cork if you don’t use appropriate protectors.

To prevent damage, seal your cork flooring with a polyurethane coating or wax. It’s also advisable to place rugs in high-traffic areas and caster cups under heavy furniture.

It Absorbs Liquids

Cork can absorb standing water and other fluids on its surface despite its waterproof nature. When this happens, cork swells, leaving behind a discolored mark.

To avoid such messes, make sure to quickly wipe off any spilled liquids on the surface of cork material.

Expansion and Contraction

Due to its elastic nature, cork expands and contracts with temperature and humidity changes.

Such fluctuations can cause unsightly gaps between the cork material and adjoining walls or floors.

When used for flooring, the expansion and contraction may lead to curling or plumping. When this happens, you’ll likely see tiles popping out or planks buckling.

An excellent way around this menace is to use a thin layer of caulk at any connecting joints to stop moisture from seeping through.

It’s Prone to Fading

You’ll likely face an aesthetic issue with cork as it’s prone to fading, especially when exposed to the elements like direct sunlight and moisture.

To prevent fading, you need to use a UV-resistant finish on the cork and keep window shades closed when the sun shines directly into a room.

You can also try rearranging furniture or area rugs to block the light.

Where to Use Cork Building Material

Walls and Facades

Cork finishes for walls are designed as patterned or plain tiles for interior and exterior applications — ideal for residential and commercial buildings. They are made from compression-molded cork for high thermal and acoustic insulation.

The material is especially suited for indoor use due to its soundproofing properties, low emissions of pollutants, and good thermal insulation.

You can go a notch higher and install a cork-based External Thermal Insulation Composite System (ETICS) for better waterproofing and reduced condensation.

Flooring

Ground and compressed cork boards make up most cork flooring. The material’s softness, shock absorption, and underfoot warmth make it suitable for residential homes, offices, and commercial spaces.

Some cork flooring options include:

• Glue-down cork flooring: Gluing a high-density agglomerated cork on a waterproof and level subfloor.
• Floating cork flooring: Comprises three layers; a lower agglomerated cork layer, an intermediate high-density layer made of wood fibers, and a top agglomerate cork layer.

Roofs and Ceilings

Cork agglomerates made from granules are ideal for ceilings and roofs. The material is lightweight, easy to install, and helps reduce energy consumption for cooling and heating.

The agglomerates are designed based on the roof’s shape and material. For instance, a pure expanded cork agglomerate suits a flat, metallic roof.

Moreover, the agglomerates are available in different finishes like asphalt-coated, colored, or thermally coated to suit different decorative tastes.

Countertops

Cork is ideal for countertop underlayment, sink liners, and kitchen countertops.

The material is lightweight and helps protect against water damage.

Alternatively, you can glue cork to an existing surface for an easier DIY installation.

A disadvantage is that its softness makes it susceptible to knives and other sharp objects like scissors. To prevent this, you need to use a sealant or wax finish to harden the surface.

Final Thoughts

Cork building material has existed for centuries and is still used in various projects. It’s durable, lightweight, shock absorbent, and soundproof.

That said, you must be ready to dig deeper into your pockets for cork material because it’s quite expensive. However, the long-term savings on energy costs and excellent acoustics can be worth the investment.

Before you leave, check out this guide to building an eco-friendly deck while staying within budget for more sustainable building inspiration.