Hempcrete blocks

What is the hemp block composed of?

The IsoHemp block consists of hemp, hydrated lime and hydraulic lime. They are 100% natural and locally sourced raw materials.

Is the hemp block hazardous to health?

The hemp block is not hazardous to health; whether for the people who produce it, install it or benefit from it in their home. The raw materials of which it is composed are 100% natural.

Can hemp blocks be used for new constructions?

Yes, hemp blocks are associated with a load-bearing structure to create envelopes for new constructions. Several possibilities are possible: wooden construction, load-bearing blocks or the IsoHemp Hempro system

Can hemp blocks be used for interior renovation?

Yes, hemp blocks allow the interior to be renovated by keeping the inertia of the building and allowing the old walls to breathe. They are particularly suitable for the interior insulation of old brick or stone walls.

Can hemp blocks be used for exterior renovation?

Yes, hemp blocks are perfectly suited for exterior renovation.

What are the possible finishes of hemp blocks indoors?

The interior finishes are varied: indoor ceiling, clay, tiles, wood cladding, etc. At IsoHemp, we have developed an interior finish: a natural rendering based on natural plaster, lime and sand ideal for finishing your walls and ceilings.

What are the possible exterior finishes of hemp blocks?

The exterior finishes are varied: siding, plaster, bricks or briquettes, etc.

What are the dimensions of the hemp block?

The hemp block has a length of 60 cm and a height of 30 cm. Only its thickness varies: 6 cm, 9 cm, 12 cm, 15 cm, 20 cm and 30 cm.

How many thicknesses are there?

There are 6 thicknesses: 6 cm, 9 cm, 12 cm, 15 cm, 20 cm and 30 cm.

What is the maximum weight of a hemp block?

The maximum weight of a hemp block varies according to the thickness and humidity content :

  • Block of 6 cm: 4.6 kg
  • Block of 9cm: 7.1kg
  • Block of 12cm: 9.2kg
  • Block of 15cm: 11.5kg
  • Block of 20cm: 15.3kg
  • Block of 30cm: 23kg

Are hemp blocks load-bearing?

No, hemp blocks are not load-bearing*. They must be associated with a supporting structure. Several construction systems can be considered: the Hempro systemwooden framepost-beam system, or supporting masonry.

* However, it is self-supporting up to 10 metres high depending on its thickness.

How do the hemp blocks adhere?

The hemp blocks are laid in a thin joint with a natural adhesive mortar. This is a lime-based mortar that is used instead of traditional mortar. The installation is done in a thin joint of around 3 mm using a glue comb or a notched trowel.

What thickness of joint must be created to glue the hemp blocks?

The hemp blocks are laid in thin joints around 3 mm thick.

Which tool is used to cut the hemp block?

Several cutting tools can be used :

  • A Widia manual saw blade;
  • An electric Alligator saw;
  • A band saw (recommended for larger sites).

Can hemp blocks be placed on the ground?

Yes. Whether it’s a renovation or a new construction, the use of hemp blocks on the ground makes it possible to insulate the slabs and is suitable for supporting a screed. This technical solution is fast and simple. The placed product is dry, which makes it possible to apply the finish very quickly.

Two systems exist for insulating your ground with hemp blocks : 

  • Slab – block – screed
  • Draining mass (telford base) – stabilised – block – screed

What are the advantages of hemp blocks for ground insulation?

  • Excellent compressive strength (15 T/m2); 
  • Speed of execution and performance over time; 
  • High technical flexibility such as the application of floor heating, the application of ducts in the screed, etc.; 
  • Easy and fast cutting; 
  • Laying of insulation in just a few hours for a complete house; 

Link to floor insulation.

Can hemp blocks be placed on the roof?

Hemp blocks can only be placed on flat roofs. For the insulation of flat concrete roofs, it’s very easy to install hemp blocks. Whatever the configuration, they are fast and easy to apply. Slope concrete is applied on which the waterproofing of the roof is then laid.

Link to flat roof insulation. 

What are the advantages of hemp blocks for roof insulation?

This solution has the advantage of quick and easy implementation on site.
With its high thermal inertia, the hemp block prevents overheating of the building in summer and guarantees excellent resistance over time.

Can the blocks be grooved and sheathed inside?

Yes. To make grooves for electricity or other technical networks, it’s recommended to use a grooving machine and a suitable hole saw.

What is the thermal conductivity of a block?

The lambda (= thermal conductivity) of an IsoHemp block is 0.071 W/mK.

What is the specific heat of a hemp block?

The specific heat of the IsoHemp block is 1600 J/KgK.

What is the density of a hemp block?

The density (= dry apparent mass density) is 340 kg/m³.

What is the lifespan of a block?

As long as the building exists and the hemp block is protected by a finish (plaster, brick, etc.), it will not degrade and its technical performance will remain intact.

Can hemp blocks be left visible?

For situations where thermal and acoustic insulation is required, it’s essential to render the hemp blocks. They are not airtight and it’s the block + rendering system that creates the technical performance. For applications where maximum sound absorption is desired, it’s possible to paint the wall directly using a spray gun or to attach a fixator to the wall.

Can hemp blocks be left outside to store them?

Hemp block pallets can be stored outside for 3 months and stored for 2 years if the pallets are covered and protected from rain.

Why choose hemp blocks for your new construction?

Hemp blocks are suitable for all types of projects. In addition, they guarantee the success of your project and have many advantages such as:

  • Thermal and acoustic performance essential to comfort
  • Natural regulation of humidity
  • Flexible design
  • Long-term durability
  • Ease of implementation
  • A wide choice of finishes: brick, parging, cladding, etc.

What are the fields of application of IsoHemp hemp blocks?

IsoHemp hemp blocks are particularly suitable for the construction of residential houses, doubling of existing walls on the inside or outside, as well as industrial subdivision and apartments.

After how long can a ceiling be placed on hemp blocks?

One week after laying the hemp blocks if the wall is dry.

Can the blocks be glued directly to the walls?

This gluing technique is used only for the implementation of hemp blocks with 6 cm thickness. The gluing of the blocks is done only against an existing uniform and flat wall. It is recommended to use a special bonding mortar that is suitable for the gluing substrate according to the manufacturer’s instructions. Do not use bonding against a wooden element.

Is it possible to tile directly on the blocks?


Must a foundation be made before laying the blocks? If so, how thick?

Hemp blocks cannot be placed on the ground directly. It is necessary to provide a foundation with a rotproof insulating block between 15 and 30 cm thick according to the stability calculations before laying the hemp blocks.

From where is it necessary to fill the space between the existing wall and the hemp block?

From 3 cm, it’s recommended to fill the gap with a mixture of ProKalk lime and hemp and a little water.

How many heaps can be made in the same day? Must it be allowed to dry after 3 or 4 heaps or can the blocks continue to be mounted?

After three heaps, it’s recommended to wait between 1 and 2 hours before resuming the masonry work.

After how long is a wall dry?

The wall is dry after one week if it’s placed in good conditions. The state of the wall depends on the state of the blocks during the implementation. If the blocks have been wetted by rain before implementation, the drying of the wall will take longer.

Are any allowances available for the blocks?

Hemp blocks benefit from different allowances and public subsidies. It is therefore necessary to set the appropriate block thickness to obtain the allowance and meet its criteria.

Must a dual flow ventilation be used despite the blocks?

Dual flow ventilation is not required when using blocks. Ventilation is nevertheless essential to ensure correct air renewal, because if the blocks are open to water vapour and rendered, they become airtight.

Are the blocks anti-allergic?

Hemp blocks are not implicated in any risk of allergies. In case of risk, be sure to use a primer and a completely natural paint as a finish.

How many 6 cm hemp blocks are there on a pallet?

120 hemp blocks.

How many 9 cm hemp blocks are there on a pallet?

78 hemp blocks.

How many 12 cm hemp blocks are there on a pallet?

60 hemp blocks.

How many 15 cm hemp blocks are there on a pallet?

48 hemp blocks.

How many 20 cm hemp blocks are there on a pallet?

36 hemp blocks.

How many 30 cm hemp blocks are there on a pallet?

24 hemp blocks.

PCS interior plaster

What is the composition of PCS natural primer?

PCS is composed of a smart mixture of natural plaster, lime and sand.

What are the application media of PCS?

PCS natural primer is a single-layer primer that is applied to all rough and absorbent substrates, both in new construction and in existing building renovations. It can be applied to hemp blocks, concrete blocks and trellises, cellular concrete and terracotta blocks and bricks.  It is suitable for all interior walls and ceilings.

Can it be placed outside too?

No, PCS is a primer exclusively reserved for indoor applications.

What thickness of PCS interior natural primer must be applied to hemp blocks?

Between 10 and 20 mm.

What are the benefits of PCS?

  • A primer open to the diffusion of water vapour
  • A healthy, natural and sustainable product
  • An economical solution
  • A smooth and ready-to-paint finish
  • Ease of implementation

How long must you wait between laying IsoHemp hemp blocks and starting the installation of PCS?

One week after laying the hemp blocks if the wall is dry.

Is PCS safe for health?

Yes, PCS is a 100% natural product that is not harmful to health.

What finish can be achieved with PCS?

PCS provides a white finish that is smooth, modern ready to paint.

Hempro system

What are the benefits of the Hempro system?

  • Speed of implementation
  • Homogeneity of the wall: only one product
  • A healthy and natural product

What is the performance of the Hempro system?

The Hempro system can be used for low-energy, very low-energy and passive buildings.

Adhesive mortar

What is adhesive mortar composed of?

It’s a mortar based on lime.

Is adhesive mortar natural?

Yes, adhesive mortar is a 100% natural product.

What is the thickness of the joints to use to glue the hemp blocks?

The block installation is done in a thin joint of around 3 mm using a glue comb or a dedicated trowel.

What is the average consumption for 3 mm thin joints?

The average consumption is 2 bags per pallet of hemp blocks.

Does adhesive mortar dry quickly?

The drying time of adhesive mortar is 36 to 72 hours.

What is the usage time of adhesive mortar?

The usage time is one hour.

What is the average consumption of adhesive mortar?

The average consumption is 2 bags per pallet of hemp blocks.

How many bags of adhesive mortar are there on a pallet?

40 bags.


Where do the raw materials used for the production of hemp blocks come from?

We maximise the short route and have different suppliers in Belgium, France and the Netherlands.

What can be used for window or door openings?

It is recommended to use IsoHemp lintels. IsoHemp lintels are prefabricated hemp concrete lintels with a reinforced concrete core used for opening doors and windows in hemp block masonry.  They are perfectly suited to new constructions and interior or exterior renovations.

Are hemp blocks fire-resistant?

With an excellent fire reaction (class B for the rendered block), they offer up to 2+ hours of fire resistance depending on the finish and the thickness of the block used.

Can we buy direct from IsoHemp?

No, we do not sell direct. We work with a network of distributors who have our products in stock.

Do you have a technical approval?

Yes, we have a technical approval issued by CSTC for IsoHemp hemp blocks. You can find it here.

Can you show a positive carbon balance for the production of IsoHemp blocks?

We have indeed conducted a Life Cycle Analysis on our products and our manufacturing process.

This analysis identified the stages of the Life Cycle where the main impacts of hemp blocks occur and validated the positive carbon balance of our IsoHemp blocks.

The impact in the Global Warming category has a value close to -100kg of CO2 stored per 1m3 of hemp blocks. This negative value indicates long-term CO2 storage that is beneficial to the environment. This LCA can be consulted and downloaded in our technical documents section.

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