HEMP, what is it ?
Hemp is a plant with similar properties to the flax plant, you will have heard of hemp rope I expect. Hemp grows 2-2.5 meters (6-8 feet) tall in one season, stalks 5-15mm in diameter, plants grows close like wheat and barley, with dense foliage.
Hemp is processed by crushing the stems, separating the fibres on the outside from the woody core. The Fibres and the seed are the valuable part of the crop. The woody core or shiv is cut into little chips; this previously a waste product is what is mixed with Lime in construction.
Hemp was widely used until the advent of synthetic fibres in the 1940-50s; it has many uses such as in rope, clothing and hundreds of other applications in the household and the construction industry.
has been successfully used in
use of lime and organic materials was widely used in
mortar has a proven record as a very durable material, in
Hemp is one of the world’s strongest natural fibre, it has been used to make cloth and rope for over 10,000 years, indeed archaeologists believe hemp to be the first plant grown for reasons other than food. Hemp can be used to make virtually anything that is currently made out of cotton, timber or petroleum. Until 1883 more than 75% of the worlds paper was made with hemp.
Hemp – A brief history
Hemp was one of the ancient world’s most important crops. Renowned for its properties in combating skin and respiratory diseases, it was also used in the manufacture of a wide range of fabrics.
Hemp is one of the world’s oldest and most versatile plants. Its first recorded use dates back to the Egyptians in the 16th century B.C. and was domesticated from a wild plant by the Chinese who developed breeding, farming and processing techniques. The fibre was used for textiles and the seeds were used for both food and medicine.
records that the Ancient Greeks used hemp to manufacture high quality fabrics
and by the 9th century hemp was being used to make rope and textiles in
the art of papermaking arrived in
During the heyday of European maritime expansion hemp fibre was of vital importance to the French, British and Spanish fleets in the manufacture of ropes and other fabrics.
In the 19th century cotton displaced hemp from the textile market and paper was also produced from other fibres. Hempseeds, a by-product of the fibre, fell out of use; this was the beginning of the decline of hemp. By the early 20th century, hemp had become a niche crop in most industrialised countries in the western world. It was very important again during the Second World War, the Americans coined the slogan “Hemp for victory” and it when it became a very important industrial crop.
the advent of synthetic fibres in the 1950’s the use of hemp declined
dramatically. Political pressure from
the chemical and timber industries (manufacturers of synthetics such as nylons
and polyesters, and the timber industry as producers of paper) with the pretext
of drug reform and concern of potential abuse.
The hemp plant, cannabis sativa is a similar
plant from which marijuana is harvested, industrial
hemp however contains only trace quantities of THC the active drug in marijuana
and is of NO use to drug users. Banning
it is a little like outlawing your garden poppy plants because in
cultivation for food and fibre has more than doubled between 1990 and 1997.
E.C. subsides for hemp cultivation were introduced in
the early ‘90s with the first cultivation licenses being issued in
FIRE CERTIFICATES AND APPROVALS
In France the hemp organization, Construire en Chanvre, (construction with hemp, web site: http://www.construction-chanvre.asso.fr/ ), a membership organization of hemp growers, hemp manufacturers, Lime producers and hemp builders is financially supported and sanctioned by the French government to provide training, technical information and research to the industry. They are currently in the process of obtaining an Agremont certificate, which would make it easier for architects and engineers to specify the product and make it eligible for Home Bond approval. The current lack of these certificates does not prevent its use, but does require a knowledgably architect or engineer to have knowledge and faith in the product in order for them to put their name on any approvals or signoffs required from lending institution.
Hemp can typically grow where cereals can be grown, and indeed makes and excellent rotational crop. It does not care for wet feet but otherwise is an easily grown and tolerant crop. Its deep roots assist in the aeration of the soil, extensive leaf droppings provide needed humus. It can be grown without the use of pesticides. The density of the plant and leaf material has the effect of suppressing weeds giving the following years crop an advantage and cutting down on pesticides that year as well. Hemp is also known to suppresses soil born pathogens, nematodes.
Harvesting hemp, baled like straw
Hemp grows 2-2.5 meters (6-8 feet) tall in one season, stalks 5-15mm in diameter, plants grows close like wheat and barley, with dense foliage
use of hemp in construction has been lead by the French where it has been
active for the last 10 years. 5-600
houses have been built in
In new Timber Frame housing, structured around the timber, like poured concrete, to form a solid masonry like wall. Usually poured at 200mm to 300mm (one foot) in thickness. It is a solid, no cavity wall. This wall surface is then plastered with a Lime based mortar to give it a normal looking finish both inside like a skim coat and outside like a nap or dash finish.
In old stone buildings, on the inside of stonewalls to provide a vapour permeably insulation level to the stonewall; this method is an ideal and healthier alternative to dry lining. Dry lining only hides problems and in 5 years you get to smell them, studies have shown that 35% of dry lined buildings over 10 years old contain toxic moulds, imagine what this is doing to our children’s health and allergies. Hemp and lime is plastered on at 20-40mm over a fresh scud coat. Takes the cold shock out of the wall with an added insulation level. Cold stone walls create ideal conditions for condensation caused by typical fluctuating temperatures in domestic buildings, this leads to the formation of mildews and the resulting damp musty smells. Lime acts to absorb excess moisture and inhibits the growth of mould. Finish coat can be a lime plaster, finished to look like any normal standard plaster wall, modern or old.
Lime or hemp is not a waterproofer, but acts to manage moisture, this is the best approach to damp problems in old buildings and is now the accepted method in the conservation industry, eliminate the source of moisture and manage the rest.
Floor insulation, when used as part of the standard conservation type floor
preparation where heavy aggregate and lime mortar is used instead of a plastic
damp course. Heavy clean aggregate
breaks capillary action of rising damp.
This Breathable floor, the conservation method, is suitable for old
stone buildings, with a lime
effectiveness of hemp was recently demonstrated in tests carried out by the top
IS THE WOODY CORE OF THE HEMP PLANT AFTER FIBOUROUS MATERIALS HAVE BEEN STRIPPED OFF. This is what is used for building material in buildings.
From the perspective of: