Making Pizza Ovens in Amsterdam

Saturday Dec 8th, Saskia and I got up at 5am and drove to Amsterdam! We had a brief pit stop for coffee and croissants which I fell on like a starving waif at 6am and regretted as soon as we arrived at Tierrofino where the most delicious, overly filling food was laid on for us. There were 6 of us on the course, and the group bonded really well. Christo Markham, the leader taught us some really interesting ways to build pizza ovens and had suggestions I'd never have thought of on my own. For example, the clay is less likely to crack if sugar is added to the mix.

This is one they made earlier and the tadelakt'd over to finish..

Free food and a free book! Bonus!

Insulate underneath with upcycled bottles, keep them in place with adobe bricks and popped clay, all stuck down with clay slip.

 Remember to make the base big enough to accommodate walls of 20cm thick and still leave room for a sizable pizza and door..

 
Level out the clay base with a wooden float and then lay the fire bricks and make them level too.

Build up the sand form, trying to keep the sides vertical as long as possible before curving into the roof.

Saskia quality checking the bricks..

 Adobe bricks, clay, sand and sugar mortar, Straw and clay slip insulation. And my enormous winter knitwear, brrrr.

 More clay, sand, sugar render with embedded jute netting to reduce cracks

While you're down there...

Sand all scooped out, looks perfect!

Examples of other amazing things to make with clay, rammed earth and tadelakt:

Hempcrete Retrofit Limburg

Monday it snowed!

With frozen fingers and hair crackling with ice, ten kids from the Antwerp Steiner School and I powered up the industrial mixer and poured kilo after kilo of lime, hemp-shiv, water and kaolin powder into it. A pack and a half of hemp to one bag of pure hydrated lime (30kilos) to about a kilo and a half of kaolin mixed with 35 litres of water makes 8 tubs worth of perfect hempcrete in about 4 minutes. This needed to be hauled upstairs and tamped by hand into the wooden forms. Our mixer was working solidly from 9am to 3pm. As your starter for 10- how many tubs did we haul?

 By the end of the day, I'd developed quite a crush on a teenager, my knuckles were swollen, I'd fallen down the last rungs of the ladder twice, torn my trousers, cut my leg, my nails were cracked, I had shiv in my eyes and I'd accidently punched a few errant screws in the walls when tamping more than once so it's taken all week for my hands to recover and get back to typing. The house looked brilliant when it was finished though and I wasn't the only clumsy one!  I also met my friend Steffi, she's a student at the Steiner school and we worked together in Vermont. It was really fantastic to see her again.

Monday night I stayed over at Peter Vos's house and talked about intelligent architectural things, had a blissfully hot shower and played monopoly the Euro version (I bought Schiphol Airport and Latvia for a bargain €160!)

Strawbale Town House

Friday was a surprise extra day with the Het Leemniscaat team and to make me feel like a real member the boss presented me with a team shirt! It's far too nice and clean to actually wear at work though, I'm saving it for best.

We drove through the frosty winter fog to the outskirts of Brussels to a residential suburban street. Thom and his wife have spent 6 months living in the sitting room of her father's small inner city apartment with their 3 children aged 6, 2 and 4 months while they created a masterpiece of natural building. Tall, narrow, squeezed into a street of townhouses, they have built themselves a timber framed, straw-bale and hempcrete family home. They are hoping to move in before Christmas and although the house looks far from finished, I am sure they will be; they have a steely determination to leave their current living arrangements.

Our job was to render the exposed bales with clay to provide a level of fire protection while maintaining building breathability. They will board over the clay on the ceilings with natural, cement-free gypsum plasterboard so that ceiling lights can be fitted snug. The walls will have a second layer of clay applied and smoothed over which will then remain exposed. They might choose to paint it later with breathable paint or a clay slip but the dry clay itself is a lovely warm terracotta colour.

I have recently discovered that I have a fear of falling from a great height and so given the slack approach to health and safety in Belgium I opted to man the clay mixer for most of the day. It was harder work than the rendering but I preferred it to the light headedly dizzy feeling I got from trying to reach too far from the top of the scaffolding with the palette knife. It was quite a short day though and best of all the sun came out at lunch time so we could all sit outside in the warm. 

This is Adrian, me and Jorn stocking up on sushi, hot tea and the papers for the afternoon.

Update: Finished house pictures, Architect Proud and Homeowners Happy..

Clay Render on a Timber-Framed Hempcrete House

Two days a week I shall be working for Mathias Lootvoet (see the last photo). His company build large scale projects from entirely natural building materials. They source their materials as locally as they can to reduce the hidden CO2 of transport and mix many of their own products to reduce commercial processing emissions. 

Despite this excellent record, I woke up at 5am yesterday morning full of nerves for my first day at Het Leemniscaat. Saskia knows him really well and spent the last week telling me all his filthy habits and exactly how hard he would be on my first day to see if I was tough enough to earn his respect. I was expecting an ogre. Or at least a bit of a git. Saskia seemed almost more nervous than me; she made me a huge thermos of Wake-Up tea and extra sandwiches because Mathias was likely to steal my food from my bag and I should have some hidden in my trousers or jacket pockets. She dropped me off at his studio at 6.30am and as I got out of the car she handed me a card with her phone number and home address on it so that I could find my way home. I felt like a refugee or a kid on her first day at playschool!

After an hour driving in the dark we arrived in a village the far side of Belgium (Belgium's small!). The site is part of a community living project. 5 families have bought and gutted a huge barn and stables built on a quadrant with an inner courtyard and garden. The existing buildings are made with beautiful red brick and terracotta tiling and to preserve them, completely freestanding timber structures have been constructed inside.

In the house we were working in this week the hempcrete had already been rammed a few weeks earlier and the wooden forms already removed from the walls so we spent the whole first day preparing the walls for the clay with reeds and a natural primer, mixed on site, made of sand, water and plant cellulose.  "Natural and delicious like porridge" says Mathias. 

The reeds are stapled to the wooden frame and beams so that the clay will have something to adhere to. The primer is only needed on boarded areas such as the shower cubicle, not on the hempcrete.  As wood responds to humidity by subtly expanding and contracting, we applied a fibre glass netting over the areas most at risk of movement to reduce cracking in the finish of the clay. Fibre glass isn't 'eco' and Het Leemniscaat is sourcing and trialing netting which works as well from other materials. So far the jute netting products have all been rejected as it gets heavy and waterlogged too easily and begins to sag down, warping the walls before they've dried properly. Flax netting is the team favourite but sourcing it locally-made is proving difficult.

I left the site at 5.30 absolutely shattered and aching all over and I'd only had responsibility for a few rolls of orange tape and an industrial staple gun.  By the time I got home I was fit only for a hot bath, a bowl of steamed veg and an early night. 

Tuesday morning saw a bright and breezy 6am departure for the site followed by a whole day of clay render shovelling, mixing, spraying and spreading with a brief but welcome stop for cake. One of the team has a weekend job at Julie's House in Gent and brought in several boxes of delicious pie shaped fun for us to scoff. I had a slice of apple tart, half a slice of tiramisu cake and a smidgeon of an incredible meringue and chocolate roulade. I could have managed more but I'm new to the team and I didn't want to come across as greedy..

The mixer can produce 40 litres of sprayable clay at a time and it was going all day long. One man sprayed the walls while the rest of us leapt to comb the clay smoothish, apply the netting and smooth again with serrated edged palate knives. The varying qualities of the palates and Stanley knives soon became obvious and the best ones were covetted fiercely. So much so that I found 3 clay coated Stanley knives in my pockets when I got home. The tools also gave unexpected rise to jokes like 'De tanden op deze kam zijn zo bot en gebroken het doet me denken aan je moeder!'* Apparently 'Yo Mama' jokes are internationally popular, who'd've thought it?

We got absolutely clarted in it, the man with the clay covered specs on is Mathias. My hair is cracking now as I type and I'm too afraid to undo my plait because I'll get clay all over the bathroom. My trousers are standing-up-on-their-own-stiff and soaked and I'm sure will still be extremely uncomfortable tomorrow. My arms ache and I've got cuts all over my hands from the scratchy clay. Bizarrely, I feel more energised than yesterday evening although I am dreading tomorrow's alarm already.

Also, in exciting extra curricular news, one of Mathias's team has invited me to a talk next Tuesday by the Belgian architect Peter Voss in Limburg. Belgium is the European leader for strawbale buildings (I learnt today) and Peter Voss is one of the leading proponents of straw construction. Excited! 

*'The teeth on this comb are so blunt and broken it reminds me of your mother!'