Not only does Mark Womersley sell natural, eco-friendly building materials - he also runs regular training courses on how to work with them.
"I trained as a planner," says Mark. "Then I got involved with regeneration schemes. I gradually moved into historic building conservation. Then I saw there was a need for someone to supply traditional materials for restoration.
"Many of the materials we supplied were permeable and breathable and they have less impact on your health and the environment. We began getting enquiries for new, green-build houses and offices and so we now supply both markets."
Mark's premises are tucked away in a corner of a huge builder's yard in Heckmondwike, West Yorkshire.
Womersley's has walk-in containers filled with paints, plasters, tools and intriguing products such as sheep's wool loft insulation. The showroom and company office are walled with straw bales which are waiting for a finishing coat of plaster. It is a hot day but the office is serenely cool.
"Some of the materials were less familiar," Mark continues. "People were asking how to use them so we started the training courses." The courses cover subjects as diverse as paint techniques, selecting lime mortar, plastic stone repair and straw bale building. Plastic? Mark assures me that the Victorians used the term to describe the substance they put on cracked and weathered bricks before what we know as plastic was invented.
People attending the courses include builders, architects and enthusiasts who want to restore their own homes. A recent course had a team of stonemasons from York Minster.
"But we don't get many painters and decorators," says Mark. "They're a stubborn lot. They're killing themselves every day with the stuff they breathe in from synthetic paints. I tell them, but they just laugh."
He gets out some paint for our photographer's benefit. It is made from natural materials and there is a lovely smell of natural turpentine. There is a tray of rich blue paint, like the blue powder paint from a primary school cupboard. Another tray is a dark pink.
"We don't usually mix with this quantity," Mark says. "I know of a big restoration project in Manchester where they do all their mixing with snack-pot cups because there is a 60ml mark on them."
There is a trestle table in the Womersley yard and surrounding it are many white drums of material, including three different grades of sand. Here and there are small walls made from stone, breezeblocks and reed fencing. These are for practice. Patches of clay and lime are still on them from previous courses.
We are in "Here's one I started earlier" mode, because the lime mixes need many days to dry and cure. A project may need three or four levels of lime and each mix is different.
Craig Butterfield is here to learn about mixing lime. The Georgians and Victorians used lime before cement was invented. In the Womersley yard it is best not to utter that word. Cement is, I am told, useful for power stations and not much else.
Craig is an exhibition designer but he is restoring a Victorian house in nearby Cleckheaton and thinking seriously about a bold career change.
Restoration is proving increasingly fascinating and fulfilling.
Mark dispenses technique and wisdom. "We had a builder from Wigan who was having a problem with his clay plaster. Some of it had fallen away. I told him to bring some pieces along.
"We put the pieces in a bucket, added some water and spread it on that wall. That's what he did to repair his building. Never mind using expensive new clay plaster. His had probably been dug out of the farmyard originally."
He goes into more detail about the health benefits. Natural paints and materials are breathable. They allow moisture in and out so that rooms do not become dry and sterile and human throats do not become dry.
Craig is astonished at what he is learning. "I feel a bit evil using some of the stuff I use in my house," he says.
Mark Womersley readily admits that he is still learning.
"Of course the stonemasons from York Minster had been using mixes for grouting that I hadn't considered. A guy from Fountains Abbey told me about adding clay to lime mortars in bridge structures to allow them to expand, which I didn't know about."
Barbara Taylor, of the Straw Bale Solutions company, takes the straw bale building course. This building style is becoming more popular and Barbara's company is working on a National Trust project at Windermere.
"The focus of our training is hands-on," she says. "We teach students to choose the best bale for building, which orientation to place the bale in, design principles, the difference between load- bearing construction and framework in-fill construction, and how moisture affects the bale. Then there is how to choose the most appropriate clay or lime mix to render the walls."
Craig Butterfield says the lime course has been brilliant. "It confirms everything you thought you should do. Now I can't wait to get back home and get started."