Structural Tradical® Hemcrete® has a typical compressive strength of around 1N/mm2 and consequently is not normally used in load bearing applications. Although it may be possible to use thick Hemcrete® walls (particularly when tamped into place) in load bearing a situation for low-rise buildings, we recommend that Tradical® Hemcrete® is used in combination with a timber (or steel or concrete) frame. In this way the frame supports the vertical loads of the roof and upper fl oors. The Tradical® Hemcrete® may be used to provide part, or all, of the racking strength of the frame subject to the particular building and design application.

Because of the use of a structural frame, the height of the building is dictated by the frame and not the Tradical® Hemcrete®. In France several multi storey buildings have been constructed for clients including the Ministry of the Environment and Housing, using Tradical® Hemcrete® and a concrete frame.

In the UK, the existing steel frame of a typical business park unit has been augmented by a secondary timber frame and the Tradical® Hemcrete® spray applied onto permanent internal formwork to create 500mm thick super-insulating monolithic walls that will allow the building running costs to be slashed.

Practical Information

Hemp Agronomy 1 Hectare = 2.5 Acres

1 Hectare will produce up to 10T of hemp (UK average is 8T)

60% of the processed hemp crop is shiv

1T of shiv is approx. 50 bales

1 bale of Tradical® HF (hemp shiv) contains 200 litres when uncompressed

1 Hectare will produce 5 to 6T of shiv (250 to 300 bales)

1 Hectare will produce enough shiv to build a small house

There are about 540,000 Ha of set aside in the UK

Carbon Dioxide 1 Hectare of hemp will absorb up to 18T of CO2

as it grows (total crop – shiv, fi bre and dust)

The shiv from 1 hectare contains about 10 to 11T CO2

Tradical® Hemcrete® wall mix contains 108kg CO2/m3 (Spray applied at a density of 330kg/m3)

Tradical® Hemcrete® wall mix contains around 150kg CO2/m3

(Shuttered and tamped at a density of 460kg/m3)

Tradical® Hemcrete® roof mix contains 155kg CO2/m3 Tradical® Hemcrete® wall mix contains 85kg CO2/m3

Walls of Houses A small semi detached house of 48 m2 GFA with 300 mm thick walls, contains 33 m3 of Tradical® Hemcrete®

This is 165 bales of Tradical® HF and 7.25T of Tradical® HB.

This will lock up 3.6T of CO2 in the walls

A small detached house of 52 m2 GFA with 300mm thick walls, contains 49 m3 of Tradical® Hemcrete®

This is 245 bales of Tradical® HF and 10.8T of Tradical® HB.

This will lock up 5.4T of CO2 in the walls

A larger detached house of 100 m2 GFA with 500 mm thick walls, contains 120 m3 of Tradical® Hemcrete®

This is 600 bales of Tradical® HF and 26.4T of Tradical® HB.

This will lock up 13.2T of CO2 in the walls

Thermal Performance – U-Values See Thermal Datasheet

300 mm wall gives 0.30 W/m2.K

400 mm wall gives 0.22 W/m2.K

500 mm wall gives 0.18 W/m2.K

Acoustic Performance See 3c: “Acoustic” in the Technical and Practical section.

Frequently Asked Questions


Design Questions

Q: Can I use smaller foundations for a Tradical® Hemcrete® house? A: Yes, you may be able to use shallower/ smaller foundations, subject to the approval of your Engineer and Local Authority Building Control Officer.

Q: How thick do the walls have to be to comply with Building Regulations? A: Yes, providing the temperature is not below 5°C and the material is protected from frost and heavy rain.

Q:Can Tradical® Hemcrete® be used in a loadbearing capacity? A: Tradical® Hemcrete® has a compressive strength of around 0.8 to 1.0N/mm2 (depending on method of application). It is normally used together with a timber frame (or steel or concrete), with the frame transferring the vertical load of the roof and upper floors. The Hemcrete® can be used to provide racking strength to the frame if required.

Q: Is Tradical® Hemcrete® available as blocks? A: Yes, blocks are available from Lime Technology Ltd (0845 603 1143). They come in two grades:

– Structural blocks Target compressive strength 3N/mm2 Thermal performance Not considered yet CO2 emission target Carbon neutral

– Thermal blocks Target compressive strength 1N/mm2 Thermal conductivity 0.11W/m2.K CO2 emission target 165kg CO2 capture/m3 (superb carbon sequestration)

Q: Is Tradical® Hemcrete® fire proof? A: Yes, in tests at the CSTB in France 300mm Hemcrete® blocks lasted for 1hr 40 minutes and then the mortar joints failed. Monolithic Hemcrete® walls should perform at least as well.

Q: Can Tradical® Hemcrete® be used for other building purposes besides walls? A: Yes, Tradical® Hemcrete® has been successfully used in France and the UK for floor slabs, roof insulation and plasters. These product ranges will be launched in the near future.

Q: Does Tradical® Hemcrete® need weather protection? A: Hemcrete® walls are normally finished with a lime render or covered with a rain-screen cladding (masonry or timber) of some sort to protect them from the weather. We expect to launch a weather proof Hemcrete®, which will not need rendering, in the near future.

Q: If it is used as an external wall does it need a cavity? A: No. Tradical® Hemcrete® provides the insulation and is used as a monolithic (solid) walling material.

Q: If used as a solid wall does it need additional insulation to comply with part L? A: No. Provided the wall is a minimum of 300mm thick it achieves a U-value of 0.3w/m3 (See thermal data sheet)

Q: Does it need movement joints when used in long walls, if so how often? A: No. The mechanical characteristics of Tradical® Hemcrete® are such that movement joints are not normally required.

Q: What protection from rising damp is required? A: A masonry plinth constructed using lime based mortar and appropriate building bricks or blocks and incorporating a standard dpc conforming to current standards is recommended.

Q: How air-tight is Tradical® Hemcrete® ? A: Because Hemcrete® is used to build monolithic walls, it is extremely air-tight and air leakage through the walls is negligible. The actual figure is approx. 0.75 g/m2/mmHg. Typical air leakage 1-3 air changes/hour @ 50 pascals


Material Selection

Q: Does Tradical® Hemcrete® have a warranty? A: Tradical® Hemcrete® carries a manufacturers warranty covering the replacement of any defective material. The contractor or sub-contractor installing the Hemcrete® would warranty the work (subject to the conditions of the contract used).

Q: Does Tradical® Hemcrete® have an Agreement Certificate? A: The process of applying for a BBA certificate has been started and it is expected that the certificate will be issued in 2008.

Q: Is Tradical® Hemcrete® approved by the NHBC or the Zurich insurance schemes? A: Tradical® Hemcrete® is approved by Zurich Insurance and complies with their low and zero carbon housing technical standards.

Q: How much does it cost to build with A: Tradical® Hemcrete® ? Cost obviously depends on scale and design, however spray applied Tradical® Hemcrete® is comparable with conventional construction costs. Please see Economics section.

Q: Is Tradical® Hemcrete® available as prefabricated panels? A: Yes, prefabricated panels are available from Modcell Ltd (07711 081262). Typically 3m x 2m.

Q: Can Tradical® Hemcrete® be used in the A: renovation of old buildings? Yes, Tradical® Hemcrete® can be used to form infill panels for historic timber framed buildings. It can also be use as an insulating plaster or render system for the thermal upgrading of masonry buildings. These applications will be launched in the near future.

Q: What is the thermal conductivity of A: Tradical® Hemcrete® ? Typically the thermal conductivity is 0.09W/m2.K

Q: How high can a building of Tradical® A: Hemcrete® be designed? The Hemcrete® is not load-bearing, so the limitation is only on the structural frame.

Q: How much CO2 is locked up in Tradical® A: Hemcrete® ? Spray applied Hemcrete® locks up around 110kg of CO2 per cubic metre. Shuttered and cast Hemcrete® locks up around 110kg to 165kg of CO2 per cubic metre, depending on the level of compaction during construction.

Q: Does Tradical® Hemcrete® breathe? A: Yes. The word breathability is often used to describe Hemcrete® buildings. There are various ways in which materials deal with moisture (water vapour permeability, capillarity and hygroscopicity). Tradical® Hemcrete® performs well in all these areas in order to provide a healthy internal environment.


Maintenance Questions

Q: Is Tradical® Hemcrete® resistant to pests? A: The Tradical® HB binder protects against rodent and insect infestation.

Q: How long will Tradical® Hemcrete® last? A: The use of plant based materials mixed with mineral binders such as lime or clay go back thousands of years. We know that the effects of the binder (high ph and good capillarity/vapour permeability) create an excellent environment in which to preserve the hemp shiv. Consequently we have confidence in anticipating a long life-span for Tradical®Hemcrete® buildings.


Construction Questions

Q: How do I know whether it is better to cast or spray the Hemcrete® in my walls? A: In general casting is used for smaller projects (less than 50-70 cubic metres) or where labour is provided by volunteers or self builders. Casting becomes more economic for larger projects (in excess of 70 cubic metres).

Q: Can Tradical® Hemcrete® be installed in the winter? A: Yes, providing the temperature is not below 5°C and the material is protected from frost and heavy rain.

Q: How do I find a contractor to use Hemcrete®? A: Your Tradical® Hemcrete® supplier will be able to give you a list of spray contractors who operate nationwide.

Q: How high can one build in a day with A: Tradical® Hemcrete® ? There is no real limit other than practical arrangements on the site.

Q: Where can I buy Tradical® Hemcrete® ? A: Tradical® Hemcrete® can be purchased directly from Lime Technology Ltd and by Special order (2 to 3 days) from most builders merchants within the Wolseley Group or supplying Castle Cement products.