Cellulose insulation

To be able to heat the house over the winter we needed to insulate the floor and roof. This we did by blowing 40cm of loose cellulose.

Put to bed for the Winter.

We bought some of the cellulose from a hardwear in Joensuu who loan out the blowing machine for no extra charge, we got the bulk of the insulation from a different cheaper supplier. We needed a more powerful generator to run the blowing machine so ended up hiring one out. After spending a week or so hand stuffing all the places that were difficult access such as under the walls and at the base of the roof section. It took 2 long days with from 3 to 5 people working, someone loading the machine Dennis on the end of the hose blowing the stuff and me running around preparing and hand compressing with the other helpers.

On the ground floor it was a simple job of blowing in between  the floor joists adding an extra 50% which is the compressed by hand. This extra 50% allows for settlement.

 

Roof showing building paper which holds the insulation.

 For the roof insulation we did it in stages, fixing on a horizontal 1,2m strip of building paper with staples then filling that space from above, then fixing the next strip of paper and filling that space. Filling the space above the window was quite tricky as there is lots of extra pieces of timber framing in the insulation space. I went around later checking how well the cellulose had filled the space by cutting a hole in the building paper and stuffing in extra cellulose where needed.

Its a dusty job but someones gotta do it!

Thank you Dennis, Dominika, Andre, Emelia and Pjotr.

Clay plastering

 In the summer of 2020 we did what felt like the biggest job of the build, over 7 tonnes of plaster!  We did some test patches to decide the mix that worked the best. Then mixed up 7 cubic meters of the stuff and shoved it on the wall.

Really though the clay plastering was a big job, tonnes of clay which had to be broken up, soaked in a pit, run thru the concrete mixer, stored in a pit again, mixed with sand, straw, hemp and horse manure with a honda rotavator, then stored again for a few days, remixing on a tarp by foot and only then putting it on the walls. 2 inches exterior and 3inches interior, phew!

 

Test patches

 

Test patches were put on thick and thin to observe what happens

 

 The mix we went with in the end for the first coat was 1 1/2 clay, 1 sand, 1 1/2 straw

Walls ready for plaster

 

Preparation  

 To get our walls ready for plastering we shaped the window surrounds with an electric strimmer to give a nice even curve.

 

 

Jute sacking stapled to the timbers which the bales are sitting on.

 

At the head of the window we stapled old jute sacking to give the plaster something to hold on to. We turned the sacking down at the corners to minimize cracking here.

 

We stapled flax felt to the edges of the window frames and where the plaster meets the timber posts. The plaster will grip the felt and the felt is fixed to the timber, so this gives a flexible joint between these materials which will open and close some as the plaster shrinks on drying and the timber moves with shrinkage also.

The gap between the floor and the base of the wall we filled to stop the floor structure getting wet with dropped plaster etc. we used a mix of straw, clay and some hemp fibers.

The big gaps in the bales we stuffed with loose straw, which was twisted in the hand to make a little plug, and then pushed tight into the gap. Some of the holes we filled with a straw clay mix.

 

Window frame with flax felt stapled on.

 

 

 Originally we had tied baling twine through the wall and around the lattice inside and the vertical timbers on the outside to hold all the elements of the wall together. After talking to some people who had some questions about the the longevity of plastic twine, I decided to tie two rows of 3mm steel wire through the wall, we connected each loop of wire with a U shaped bolt connector. Hopefully this stuff will hold up.

 

 

3mm thru wire with U bolt connectors to replace baling twine.

 

Mixing plaster

For the first coat we used the straw we had saved from strimming the bales earlier, when this ran out we just strimmed more in an old milk churn into about 5cm lengths.

We made a mixing pit on our gravel road, this got deeper and deeper as we did more mixing.

The wet clay slip was mixed with sand in the wheel barrow and in buckets using a mixing drill. This was poured out on the ground of the mixing pit. The cut straw we then added in 3 stages to this, mixing it well in between each one.

 

 

Mixing sand and clay slip.

 1 mix has 160 liters of sand, 240 liters clay slip and 240 liters of chopped straw. We made 11 mixes for the first coat.

Pouring in mixing pit.

Adding chopped straw.

Mixing with modified honda rotavator

The rotavator has two plywood wheels added to the outside, when i first tried the machine was pulling up lots of the gravel base and quite quickly digging itself into a hole.

Shoveling mixed plaster onto tarp for storage.

The mixed plaster was left to mature for a minimum of 2 days, this gives time for the straw to rot just a little which makes it softer and so the plaster is easier to use. I read that the rotting straw gives some helpfull effects to the plaster; stickier so nicer to put on, and once dried it is more tough and a bit more water resistant.

Shoveling the mixed plaster was the most physical part of the mixing, so usually I got Marja muscles to do it! 2 mixes was enough to do in a day, we had 7 mixes ready before plastering began.

 

So whats next?

Talkoot work gathering

 

To help with the plastering we organized a week long talkoot. 14 different amazing people came for different amounts of time and helped us with this big job, it would have been very difficult to get so much work done otherwise.

 

Visa, Taina, Tiina, Pjotr, Pekka, Dennis, Karola, Huck, Marja and Mick. Photo taken by Kaisa.

Covering timber with plastic.

We remixed the plaster from the storage pit by foot on a tarpaulin, the tarp is also pulled from the corners to turn over the mix. We added a small amount of fresh clay slip which seemed to liven up the plaster a bit and made it stickier.

 

Remixing on tarp on the right is the ready mixed stuff.

The straw bales need to be coated with clay slip before applying the plaster. The slip should cover each strand of straw, we applied it by hand massaging it into the wall. We added some sand to the slip which to make it easier to pick up, it needs to be stiff enough that it stays in the hand and liquid enough that its easy to smear on the bale.

Feet and legs mixing slip before using.

Applying clay slip

 

The first coat on the interior walls is 5cm thick flush with the wooden lattice. There are no sharp corners in the plaster as it would chip and the curvy shapes are much nicer looking.

First day of talkoot.

Marja plastering above window opening.

Tiina adding more staples to jute sacking at window.

Clay slip pit dancing.

 

More clay being broken up ready for the soaking pit

Washing pit.

 

Exterior rendering.

 

In the 7 days of the talkoot we got the inside first coat finished and the exterior started on the last day. Over the next couple of weeks we got all the exterior first coat finished.

 

Preparing for second coat. 

On the exterior where the floor meets the wall there is no straw bale so we needed to add a surface to put the plaster on. We used plaster lath, which is thin pieces of wood with a space between each piece so some of the plaster squeezes through and around the laths and the plaster kind of hangs from this.

Trim and lath ready for render.

To protect from damage at the base of the wall we bent 25mm x 50mm aspen trim. The top and bottom are sloped to shed water. We first soaked the pieces in water for a few days, then clamped them in a form and allowed to dry. The form is made so the pieces are over bent by 15%. I used an electric fan to speed up the drying so I would be able to fit them before the second talkoot.

We also fitted the windows which really changed the house, no longer could a gust of wind be heard in the trees.

Form for bending aspen trim.

200mm pipe for soaking aspen trim

 

For the second coat we made a mix consisting of 1 sand, 1 1/2 clay, 1 straw, 1/2 hemp and 3/4 horse poo.

 

Second coat test patches.

Second Talkoot

For doing the second coat on the exterior we organized another week long talkoot (we don't have pictures). We got the outside render finished in the week, some of the people from the first talkoot came back to help again. Thank you all so much.

The second coat is a bit more work as it needed to be finished. We first wet the wall down with a hand sprayer, applied the plaster using hands then flattened it out using a wooden trowel. Each day we started from where we finished the day before, in this way the joint from the new plaster to the old is easier to conceal as the older stuff has not dried out too much.

Interior plaster

 

 

Over the next couple of weeks Marja did the finish coat on the interior while I tried to keep ahead of her fitting the window boards. Marja explains below what she did.

For the interior plastering it was important to plaster the whole section between two posts (otherwise there would have come a visible line of where the plastering was finished one day and started the next day). This meant a long day of plastering. I got everything ready the day before so that the day of the plastering I would only need to remix the plaster and then start plastering. Before plastering the wall needed to be sprayed wet. That took a surprisingly long time.

 

 

 

For the second layer it was more important that the result would look good since we will be looking at it for ever. It took some practice to make the finish look good. Also there was not much time from when the plaster was put on the wall to when it was too dry to smooth. After wetting a small area the plaster was placed as thick as needed in the small area. Then this area was smoothed a bit using a wooden trowel. This would be repeated in about four small areas and then it all was smoothed the final time. The more time I had the more precise the end result was. Marja.

 

An oat grain sprouting in the plaster.

 

Mummified rat on temporary display in our truth window.

Some nicely shaped pieces from a pine tree stump set in the plaster.

We plastered the last wall in October and it was the wall with the pine stump pieces in it, which meant the plaster went on quite thick about 5cm. Also now we had the windows closed to be able to heat the house. This made this wall very slow to dry, after a couple of months it still looked wet so I used an electric fan to get it dry.

 Wood fiber board wind protection layer to floor.

Before the cellulouse insulation can be put in we needed to seal the underside of the floor. This we did by fitting 28mm wood fibre board to the underside of the floor joists. The wood fibre board carries the insulation acts as a wind protection layer and minimizes cold bridging.

Little people off to work.

Spring time

Ground floor from inside with fitted wood fibre board on the left

Also the outside edge of the 400mm deep floor needs to be sealed. Here we used 12mm bitumen impregnated wood fibre board, this can get a bit wet without suffering permanent damage. Also we fitted some of the floor insulation which would be difficult to access from the inside and almost impossible to do a good job on once the wood fibre board is fitted.

Outside edge of floor with wood fibre insulation.

We fitted extra strips of board at the base of the straw bale wall to stop any air leakage where the floor meets the wall.

Bitumen impregnated wood fibre board.

At the top of the wall where it meets the roof we also had to fit 12mm wood fibre board to close this junction. This was quite a challenge as it is an awkward spot and the board needed to be shaped to the round wood rafters.

 

Floor from underneath the house.

 

The underside of the floor we then covered with 4"x1"s screwed with 6x90mm stainless steel screws. these boards support the weight of the insulation and protect the wood fibre board from being damaged. Small animals like to use it for building nests! We will treat them with wood tar paint later.

 Wall stablizing lattice

 So after my hand got back in working condition we started to fit the yurt type lattice. I'm not so sure this was necessary, as the movement seemed to be gone from the structure after the straw bales were done. The walls now had 2 additional horizontal members, the tops and bases of the windows and between them the 4X2's which sandwich down the bales.

But to be really sure there would be no horizontal movement when the wind picks up we added a lattice made up of 2X1 inch timbers. These we prebent by stacking them fresh from the saw mill, supporting them at either end and putting big rocks to press them down in the middle. I later found out I should have bent them an extra 15% to allow for bounce back.

Prebending the 2X1's. Thanks Jakob and Pirmin for lifting up these big rocks!

 

The lattice is made up of a double layer of 2X1's (50X25mm) fixed top and bottom with 6x100mm screws. Each cross gets a 5x50mm screw.

When we started the lattice I just pushed each one against the bale by hand and had a helper fix them at the top and bottom ends. After doing one wall like this I realized the wall was bulging in. So for the other walls each pieced was clamped by pushing one or two sash clamps thru the wall and really squeezing the 2x1 into the bale. Each one needed to be over bent to end up with an evenly curving wall.

After bending a piece we would tie it in place using baling twine thru the wall, then fix the next one. This was a very time consuming job, each of the 9 sections took about a week.

If I was to do it again I would try to build the lattice first and build the straw bales up against it. But its nice to feel sure that there should not be any movement from the wind loads.

Straw bale walls

This is what its all about. Funny how little time was actually spent doing the straw bale walls, we started with 4 of us, then 2 for most of it and I was finishing it alone. Later there is a safety warning!

Reciprocating saw with long blade for notching bales and a bale needle for retying bales.

 

 

 Retying a half bale

Window frame 200mm X 50mm boards fixed to 100 X 100 posts.

South South East window

 

Large South window with lattice underneath.

The bales below the window opening are pre compressed by putting heavy duty ratchet straps and tightening them to the max. The strap goes over a 4X2 inch timber ladder which holds down the bales and then the base of the window frame is notched into the posts and wedged and nailed.

Top of window frame notched into 100 X 100 posts.

 On the wide windows over 1 meter span a doubled 200 X 50mm header is notched into the 4 X 4 inch posts.

 Every 3 or 4 courses of bales a 100 X 50mm horizontal brace is forced down as much as possible and nailed with 5 inch nails to the posts. This helps to stabilize the straw bales.

 

 Howdy!

 

 

 

In September 2019 as I was fitting the third last bale, while standing on a carpenters stool on the scaffolding with no handrails and just some plastic sheeting between me and the ground 3 meters below, and loose straw everywhere, the stool slipped and I fell and broke my arm and fractured my pelvis. We now have some handrails fitted, a hard way to learn a lesson.

 

 

 Time to take a rest for a little while.