Is Hempcrete Fireproof – A Closer Look At Hemp Buildings

The housing markets are around the world have really been shaken up in recent years as their prices rise and alternative housing options continue to soar in popularity.

While some of these alternative building materials are more gimmicky than providing real cost and performance benefits, Hempcrete is one of the building materials that is growing rapidly in popularity and seems to have a lot going for it.

As with any ‘new’ building material, there is going to be plenty of criticism and scrutiny before it is accepted by the public.

Claims that hempcrete is carbon negative, fireproof and waterproof are often seen as exaggerated but in today’s article we will take a look at just how effective it is at preventing fires and how it defends it’s other impressive claims.

Hempcrete has been proven to be fireproof in a number of key tests, including a recent ASTM E84 test carried out by the guys at hempitecture.


What Exactly Is Hempcrete

Hempcrete is a mixture of hemp hurd, lime binder and water.

By mixing 4 parts hemp hurd with 1 part lime and 1 part water, you are left with a surprisingly strong building material that is not load baring but is certainly strong enough for walls.

Hempcrete can be used in a similar way to rammed earth, compressing the material into a wooden cast system where the wall is to stand.

It can also be made into load baring bricks which is becoming more common and spread over existing walls for insulation.


Just How Fireproof Is Hempcrete

Out of a flamedex index score of 0 – 450, with 450 being the most flammable, hempcrete scored 0, making it the most fire resistant building material on the market.

Hempcrete can withstand direct fire for over 2 hours without igniting at all.

So, the claims are true, hempcrete is fireproof but that is not where the story ends.


Importance of the ASTM E84 Test

The ASTM E84 is a crucial moment for Hemp as a building material in the United States as there is now an official test on record that proves just how fire resistant hempcrete is.

While it will still depend on how the material is mixed, hempcrete has been proven as a fireproof building material.


How Good Is Hempcrete For Insulation

When building with concrete on another material, you will need to use insulation, like fibreglass which is also flame resistant but can melt and release dangerous chemicals into the air.

Hempcrete is a natural, non toxic insulator with an impressive R Value of 3.5 per inch which is in line with other insulation materials.

You can complete your hempcrete walls with hemp line plaster for a natural and effective insulation strategy.


Is Hempcrete Waterproof?

Hempcrete is not only for resistant but it can also deal with large amounts of water without issue.

The fibres in the hempcrete can store a lot of water and the lime that is present in the material prevents any mould or rot from developing.

Hempcrete can hold a lot of moisture that will be released when conditions allow but the drying process can also be accelerated.


Can Hempcrete Withstand An Earthquake?

Surprisingly for some, hempcrete is resilient and very hard to crack and while it is not load bearing in its natural form, it will be very hard for an earthquake to crack hempcrete making it essentially earth quake proof?


Hempcrete Does Well In Humid And Cold Climates

Hempcrete is a breathable substance, meaning it stores up heat when the weather is hot and releases it slowly over time when the sun goes down.

This ensures you have less need to heat the structure with a fire or electric heater, also reducing the risk of a fire within the building.

The same is true in cold climates where Hemps natural insulating properties allow to perform better than traditional building materials.


Hempcrete is Carbon Negative

Traditional building materials can have a negative impact on the environment but since hemp holds carbon dioxide inside, a hempcrete building actually removes carbon from the atmosphere and stores it in the building.

When the building is no longer needed, the hempcrete is biodegradable, recycleable and resusable, even as fertilizer, which ensures a environmentally friendly building material, throughout the life cycle.


Hempcrete Is Non Toxic

The hemp plant is a natural pesticide, you don’t have to spray it with harsh chemicals while it grows and the whole plant is usable resulting in little to no waste.

The lime in the material also keeps pests away from the actual building which is another bonus.


Hempcrete Is Not Load Bearing

One issue with hempcrete is that it is not as strong as concrete and is not load bearing in nature.

To combat this, plenty of hempcrete contractors have started making hempcrete bricks and blocks which are much strong and can support loads.

Otherwise, you would need to use hempcrete is a traditional or timber frame construction which would support the weight.



The building revolution continues and materials like Hempcrete are becoming much more popular.

Since Hemp is now legal again, all around the world, the use of Hempcrete is seeing a boom in recent times.

With all of the positive aspects of the material, it is easy to see why.

When you use hempcrete in you building, fire in the home is a threat that you can spend less time worrying about.