Lime Rendering and Limewash

October 4th. It has been difficult to keep this blog updated during the lime plastering. I have generally been leading with pictures and writing a little explanation; but the three coats of lime render and four coats of limewash all look remarkably similar, so I haven't been taking many photos lately.

Lime Render, Coat 1. The mix for this was 1 part lime putty to 2 parts sand. It used about 8 x 18litre pots of lime putty. Greg and I got around 2/3rds of it done in three days, and it was finished off on September 6th - the mass participation event.

Lime Render, Coat 2. I used a 3-to-1 mix with added chopped straw. After a certain amount of experimentation, I found that the easiest way to chop straw was to sprinkle it about and the run the lawn mower over it a few times. This coat was around 10 - 15mm thick. It took 18 to 20 pots of lime putty. We did around half of it on September 6th, and the remainder over the next three days

Lime Render, Coat 3. Same mix as coat 2, but without the straw. I was planning to make this about 5mm thick, but I think it came out thicker - perhaps as much as 10mm. There was a certain amount of hard-trowelling to level, but I finished the surface by hand. About 10 pots of putty, and about 15 person-days work. I finished the rendering with Chris on September 19th, 2 weeks and 2 days after starting.

September 12th - Jane & Harriet working on second coat

Jane and Tessa

Finish coat applied to scratched body coat.

Last section!

Limewash

I spent the fourth week of September having a big clear-up around the site, and getting on with some long-neglected non-building jobs. This week, September 29 - Oct 3rd, I have applied 4 coats of limewash.

Second coat with raw umber pigment covering white first coat

Same colour! Wet on left, dry on right.

The limewash is essentially the same material as the lime render. You start with lime putty, but add water instead of sand. To apply a coat of limewash is really just to wet the surface with the limewash and let it dry. It's quite different to painting: there is no tension between the surface and the paint, so can be applied very quickly. My final coat was applied in under 3 hours.

Lime Rendering

September 8th. So, having only taken the punch-and-judy tarps off recently to expose the straw walls, I have been busy covering them with lime render. It's a great shame that this is necessary; it would be great to leave the straw exposed. I think a roof overhang of about two metres all round would be sufficient. It would also save a lot of work.

Luckily I have had a lot of help this week; new POOSHer Greg has been here all week, and I had 9 friends here on Saturday and 3 on Sunday. And dry weather all week. As a result, the exterior render is over half way done.

First job: stuff the holes.

Second job: trim loose straw with a hedgecutter. "Before" and "After" photos

                        

 

It didn't look greatly different, but there was a lot of straw on the floor, and it would have needed more lime if it had been on the walls.

There is an inspiring quote on the POOSH site that goes: "If you're not sure how to do something, start!" So, I've read all I can about lime rendering, but I've only done a couple of hours before, and it kept falling off the wall. But there's nothing to be done now except get on with it!

First time I have mixed lime putty. It's wonderful stuff - much stickier than NHL mortar. Seems to be staying on alright. The photo below shows current POOSHer Greg adding a pot of lime putty to the mixer; the grid on top is useful for slicing a large block of putty up into strips.

POOSHers are sustainable building volunteers who come and help with a project in return for food, accommodation and work experience. It's a network similar to WWOOF that runs on the site www.thepoosh.org . All our POOSHers this year - there have been lots of photos of them - have been absolutely wonderful: good company, good guests (cooking, washing up, etc.) and hard working - I wouldn't have got the building up without them.

However, I haven't been overwhelmed by people wanting to come and volunteer here. I think I've had 9 all counted - and that includes 2 who came for one day only, and one friend-of-friend who registered on POOSH after coming here. So on Saturday, I had a "Lime Rendering Party" and asked lots of my friends to come. There were 14 people here, and I think they had a good time slapping on some lime. 

My (gloved) hands were covered in plaster all day, so thanks to Jim Froud for the pictures:

and one video!

Made of Straw

I have been taking the scaffolding down this weekend. Whilst I was at it, I thought I would take the side tarps down to take a photo of the building in its finished but unrendered state. When it's all covered in render, I will want to remind myself of what it's made of.

This is three months work. At the end of May, there was just the stem wall here.

It looks a little miniature here, so here's one with me in it, for scale:

And a side elevation:

It's a great feeling to get the site tidied up. Here's the two-tons of scaffolding ready to return to Suffolk:

and the monster truck needed for getting it there.

Green Roof

August 11th. Planting the roof.

The roof has been taking longer than expected. I was hoping to finish around the 20th July - so running about three weeks behind schedule. Adding the skylight was a late addition to the plan, and other aspects have taken more time because of the size of the roof. At around 55 square metres, it is a giant; you could have a game of tennis up there.

On my last blog, I showed pictures of bulk bags of cockle shells and 3 - 8mm leca, and of the shells spread on the roofing membranes as a drainage layer. After completing the shell layer, I put a single line of flint cobbles around the roof deck. They are sitting on a layer of RFG to raise them up to be visible over the retaining boards.

Then it was time to mix the substrate - the lightweight growing medium for the plants. I was aiming for a substrate thickness of 2 - 3 inches (50 - 75 mm). My ingredients for the substrate mix were: 

• 3 - 8mm leca. These are fired clay particles used as a lightweight aggregate or insulation. They look like cocopops.
• Coir fibre. Sadly, I took no photos of the coir fibre before mixing. It arrives in 5 Kg blocks the size of a large shoebox. You add water to reconstitute it, and after you have added a lot of water and forked it over, you get a heaped wheelbarrow full of fibre from one block.
• Expanded Perlite. Perlite is a volcanic glass with a high water content. When heated, the water evaporates and leaves a lightweight honeycomb glass structure. I used a 3mm grade.
• Sharp sand
• Crushed rubble. I put a mix of everything in here: all the remaining RFG, some mortar from the demolition of a garden wall (source of my stem wall bricks), crushed brick. It all had to be crushed with a tamping rod.

The mix evolved as I went along, mainly to make full use of the materials I had bought. It started out as: 3 leca, 3 coir, 1 sand and 1 perlite (= 4 buckets); by the end, the final mix was 2 leca, 4 coir, 1 sand, 1 rubble and 1 perlite (4.5 buckets). The whole roof took around 55 mixes, roughly 1 mix for each square metre of roof.

Crushing rubble

Loading the forced action mixer with coir.

Two or three minutes later, filling sacks with well-mixed substrate.

No, I haven't got a hoist!

Using roofing battens on edge to regulate the depth - approximately.

Last strip of substrate. Actually, you can see I have already planted some of the roof here, but I'm going to go back a step to talk about the plants.

Plants: We want some drought-resistant,  ground-covering plants for the roof, to hold the substrate in place and green the upper surface. Sedum is recommended. You can buy beautiful ready-grown sedum mats and unroll them on your roof, but with 55 square metres of roof to cover this would cost thousands of pounds, so we have another plan.

We asked our friends what they had. In some cases, we were even cheekier and asked people we didn't know if they could spare some plants! We were very kindly given a large tray of creeping thyme, a small tray of semper viviens, and as much wild sedum as we could dig up.

This is our source of sedum. It's a concrete road circa 1941 on an old USAF Norfolk airbase, currently used for storage of potentially recyclable materials. We bagged up a small proportion of this.

                     

      

Then we divided the clumps, and planted plugs of plants at 9 inch separation over the whole roof area.

Until it looked like this:

With thanks to the roofing crew: Chris, Adam & Izzy.