Render Colour Chosen

We have decide to render the inside and outside of the house all one colour, to give the illusion that the solid walls are that colour all the way through, so the choice of colour will have a big impact on the look of the house. A light, but warm, yellow is the colour we are aiming for. Originally we were trying to achieve a sand colour until we realised how brown a lot of sand is.  Our light yellow is an idealised version of the colour of sand or chopped hemp fibre.

After initially dismissing the use of Builders brand oxide in 420 Yellow, we reconsidered it when compared to some paint swatches we got from the hardware store the other oxide colours we had tested were too orange or too brown. Our objection to the yellow was its intensity so we tried some very pale versions at 0.2% and 0.4% (Our earlier tests had been 1% and 2% but had been done with unreliable scales. Scales than only measure in 1g increments are not accurate enough when trying to measure a weight of 2 grams ). These tests did not give enough colour to overcome the underlying green grey tinge of the lime render mix. 

Further tests were carried out, both on the hemp wall and on the MgO  board, using 0.6% yellow, 0.8% yellow, 0.6% yellow and 0.2% sundance, and 0.6% yellow and 0.2% sandstone. These tests were measured out using a tiny tube cap as my jewellery scales ordered from e-bay had not yet arrived. Later after I received the jewellery scales, accurate to 0.01g, I found that one capful was 0.45g which when doing 1/40^th of a mix was 0.2%. We have done all our render tests on the wall behind where the kitchen cupboards will go, but were running out of room, so we used a hammer and cold chisel to chip off some of the render colours we definitely were not going to use. Pleasingly the render did not pull off easily and was well adhered to the wall, but ultimately came away with minimal damage to the hemp wall underneath. 

Top centre: Chosen colour 0.8% yellow

4th from left: 0.8% yellow on MgO and Top far right wet test of same mix

The further render test colours were all close together which enabled a finer comparison. Even though the colours were close together 0.8% yellow was clearly the best. The lighter yellow (0.6%) lacked sufficient colour, but any darker that 0.8% would have been darker than the “light yellow” colour we wanted.  As it was our chosen colour was darker than the paint swatches we were comparing it to, but it was difficult to make a direct comparison between different products. We checked the 0.8% yellow render against the plywood ceiling and the hardwood window revels and door jambs and the dark grey polished concrete. It was satisfactory against all these materials. We then moved the MgO board outside to see what the render looked like in bright sunlight, and it was still satisfactory. 0.8% yellow has tentatively been chosen. This will translate to 72g of oxide per 9kg bag of render. To check that we have got the measurements correct and can replicate the colour we like we did a further test of 0.8% yellow. We have yet to see this check patch dry.

It is fortunate that we have a render colour, as on the recommendation of our neighbours we met up with John the renderer. He was experienced with a variety of renders and was keen to try a new product, the hemp lime render. We realised it was unlikely that we would be able to achieve a consistent render finish and that it was likely, without experience, that the rendering would take us a long time.  Next time we are on site we have arranged with John to do a section on the inside of one of the wardrobes, so he can see what the product is like to use and work out the finish we want.  We used offcuts of the good ply to finish the ceiling of the robe so it can be sheeted and ready for rendering.

Wardrobe ceiling added

The last two of the cavity sliding door units have been installed. One of the cavity sliders that is not supported at the opening end by a perpendicular wall was a little bit wobbly as when the top and sides were level the bottom of the opening jamb was off the ground. I will have to find some thin masonry anchors to put through the bottom side rails into the concrete floor.

Cavity sliding door units installed

 With the last of the cavity sliding door units in we were able to continue with sheeting the internal walls. I borrowed some fibro cutters from a friend, Martin who has helped out on the build on several occasions. I was amazed that the fibro cutters were easily able to cut through the 8mm MgO board. I just had a little trouble cutting on my marked line and keeping the cut straight. I will practise further with the fibro cutters before I choose my preferred method of cutting the MgO boards.

Internal walls being sheeted with MgO Board

An unusual detail that we discovered while building the walls was that one of the studs at the door opening was set in from the line of the cast hemp wall. This meant that the wall was further out than the stud. When I came to install the door jamb it all worked out very well. I am using 19mm Tassie Oak for my door jambs. I used an angle grinder to cut into the hemp wall to enable me to set the 126mm wide door jamb flush on the stud. When the wall is rendered the 10mm render will come up flush with the door jamb and instead of being a problem this will now give a neat finish.

Hemp wall cut away with angle grinder

Close up of the cut away hemp

The large awning on the north side of the main room had a dip were the two parts of the fascia board were joined. I had been reluctant and unsure how to tackle this problem. My neighbour from home, James, was in Nowra for the weekend and we  recruited him to use his building experience to help us solve this problem. After some thought and discussion the shorter end section was removed and the longer section cut and 2/3rds of it removed so that a single long piece of fascia could be used to replace the pieces removed.

Awning propped and new piece added

 First we used some props to level the remaining pieces of the fascia. It was amazing to see how much the awning had dropped and how much more movement it had in it, since we installed it in January. Further props were added and levelled where the join would be and at the far end, this enabled us to rest the long fascia board on them rather than having to try and hold it. With everything level two batten screws went in at every awning rafter and a cleat was attached to the back of the join of the fascia, which was between to rafters, rather than my previous mistake of jointing the fascia on the rafters and not using a cleat. The result was beautiful. I can look at it proudly and see that it is level. Now I can put the battens on ready for the corrugated roofing to go on. I will also go back and re level and prop the other awnings and leave the props in place until I can put some steel cable in from the awning to the rafters of the roof above, to prevent the awning drooping in the future. 

Straightened awning looking beautiful

 I am still hopeful of being being able able to negotiate an acceptable outcome to the “blue marks on the ply” problem. To avoid any miscommunication and to try and get something happening faster I am now dealing with the distributor, Gunnersons, rather than the local retail supplier I got the ply from. While we resolve this issue it seems we will get on with building the rest of the house and have to leave the main kitchen/living room, bathrooms, laundry and entry unfinished until I can get a product I can use for a ceiling.

Installing Cavity Sliding Doors

With no replacement ply arriving in time for the weekend the ceiling remains unfinished six weeks after work stopped on it.  A few phone calls to arrange some timber and work started again on site with the installation of the cavity sliding door units. I purchased the Hume Statesman cavity sliding door units from Bunnings about a year ago as I originally thought they had to be put in at the same time the frame went up. This was not the case, but the units had to be installed now so that I could sheet up the internal walls around them.

The cavity sliding door units are made up for a standard 90mm frame sheeted with plasterboard. As my internal walls are sheeted with 8mm MgO board and finished with 10mm of render I needed the door frame sections to be 10mm wider than those supplied on the units. Like the window reveals I intend to use the door frames as render stops. Having to change the door frame timber I took the opportunity to replace with with Tassie Oak hardwood to match the window reveals. I got the timber from Ison Hardware in Bridge St Nowra where they mill the timber on site, this enables me to get the non standard size of 19 x 126mm for my door closing jambs. The measurement of 126mm is made up of 90mm for the frame 8mm each side for the MgO board and 10mm each side for render. With the help of a little planing of the top of the jamb they all fitted together.

The timbers replaced it was time to install the units. The first one was not too difficult. I did a lot of levelling, the split jambs, the top jamb and closing jamb and the back of the unit, but will only be able to tell if I have done a good enough job once the doors are hung. Since I do not have the doors yet, I will only find out after the walls have been sheeted and rendered. I backed in behind the gap at the back of the unit and attached it to the frame with the framing gun. The unit was attached with screws at the top and I used brads to attach the closing jamb and to attach the cavity unit to the frame where they came into contact, taking care not to leave anything sticking into the section where the door slides.

First cavity sliding unit installed

Beautiful hardwood closing jamb

The second cavity slider unit was the difficult one as it had to be slid into a slot in the frame. There was not enough room to put it in with the top rail attached as per the instructions and the angles and small amount of space left around the door meant that the top rail could not be slid in either before or after the door. The only option was to take a small section out of the stud next to where the top rail would go, slide the top rail in sideways and attach the top rail to the cavity sliding unit after it was in place by twisting it slightly sideways to get the screws in. The stud that was cut was attached by a noggin just under the cut as well as just above it so that it was still held reasonably well even though it was cut. After the cavity sliding door unit was installed the cut stud was repaired with an extra piece attached to the side.

The awkward cavity slider unit installed

We also sanded and applied an oil finish to the timber reveals on some of the windows and one of the door jambs. We used Livos Ardvos natural wood oil. It was easy to put on with one of the pads used for edging and a fine paintbrush to fill in the corners. I was very happy with the finished colour and will do another coat of Livos oil after the walls have been rendered. I filled the screw holes in the window reveals with "Hardwood"colour wood putty, but the filled holes were very obvious as it never quite matched the variable colours of the timber.

Livos Ardvos Wood Oil

Oiled window frame

Oiled sliding door frame

A weekend of work on the build would not be complete without more render tests. After last time writing off the yellow colour  we came to the conclusion that we preferred a yellower colour to an orange or brown colour. With the existing Yellow render tests considered too dark/intense I tried some really pale versions. My new scales had not yet arrives (they were in the letterbox when I got home) so I was doing measurements using tiny cap fulls. Unfortunately there was not enough colour in these test of one and two cap fulls to 1/40th of a bang of render, to overcome the grey/green tinge of the render. So, further render test were done, including blending the Yellow and Sundance oxides together. When wet all these tests looked almost the same, so I will have to wait until they dry to see the results.

2% and 1% Yellow, 1% Sandstone, 4%, 3%, 1% and 2% Sundance oxide

Two and one cap fulls on Yellow oxide

Using Magnesium Oxide Board

Unable to finish the ceilings, while we wait to try and exchange the plywood, we started on the magnesium oxide board internal walls. We chose to use the magnesium oxide board (MgO board) as it is breathable and therefore compatible with the hemp walls, but it is also fire proof, mould proof, rot proof. MgO board in a relatively new product in Australia, it is all made in China. Price wise it is cheaper than fibro but more expensive than plasterboard. I researched the Internet for fixing and cutting methods. It was recommended that the MgO board be cut with a jigsaw or a low speed circular saw. I have a circular saw but it is only a high speed one and I did not want to blunt the blade and did not use it. The other option is to score and snap the board but I was not confident that this would give a neat join with an 8mm board. So I used my jigsaw. I quickly blunted the first blade but did not take notice of how sharp the blade was in the first place, so I changed the blade. After two or three cuts the new blade was also blunt. I went to the local hardware store to get a fibre cement blade, as I had been using wood blades, only to find out the no such blade exists. I queried how people cut fibre cement sheets and was shown a tool that looked a bit like a pair of bolt cutters. These would never work on the 8mm MgO sheets. The alternative suggestion was an angle grinder with a masonry blade.

I tried cutting the MgO boards with the angle grinder. it worked well and was easy to get a nice straight line. It was dustier than the jigsaw, but the masonry blade was still going well after more than 20 cuts. The dust is supposed to be non toxic, but any dust is bad, so I made sure I used eye protection and a dust mask when cutting the boards. Cutting the boards was straightforward and not difficult. I set up a large flat area with a couple of movable spare OSB boards, reused from the formwork, so I could make a gap where I needed to cut and leave the remainder of the board supported. This worked well.

The MgO boards are fixed with screws and the boards can be laid vertically or horizontally, depending on the wall dimensions. Vertical joints should be on studs and fixed each 200mm on edges and 300mm centres on intermediate studs. However the instructions also state that the boards should not be fixed with in 60mm of corners, presumably so the corners do not crack off. Also the edge fixings need to be 12mm from the edge, presumable also to prevent cracking. With 40mm wide studs this allowed just enough room to join the boards on a stud. The boards were tapered at the edges so if you were painting them you could tape and fill the joins. As I am rendering the internal walls, so they look the same as the external walls, I am not doing this, but will use a render mesh.

Cut sheet of MgO board installed

Several sheets of MgO board put up

I went to a large chain hardware store looking for fibre cement screws, they have a different tip and cutting barbs under the countersunk head. The hardware store did not have any fibre cement screws so I bought a packet of galvanised timber screws that looked like they had some barbs under the countersunk head. The timber screws worked but were a pain to put in, and were slow, you had to push really hard to get the countersunk heads to go flush without shredding the Phillips head in the screws.

A week later I sourced a box of 1,000 30mm galvanised fibre cement screws with square heads from Nepean Boltmaster.  These were great, went in easy, no chance of shredding the thread. Fibre cement screws were recommended and they definitely make the job easier.

Timber screw in left, fibre cement screw on right

I was one bag of insulation short to finish the house, plus I had not bought insulation for the hallway. I bought the sheep's wool directly form Higgins Insulation and picked it up from their Villawood warehouse to save transport costs. When I complained about one bag of insulation being a batt short and one bag being misshapen, I was advised that their Sydney operation had closed down. Then when I called head office in Queensland I found out that although the Sydney operation had the same "Higgins" name it was separately owned, this meant that I could not do anything about my missing batt and if I wanted to finish the house in sheep's wool I would have to get it from Queensland. If I was going to get one extra bag of insulation, I decided that I might as well do the thinner raftered hallway in sheep's wool insulation as well.

Four not five batts

Misshapen batts, correct batt in the centre

I ordered three bags of R3.0 580 x 1200mm batts. Higgins in Queensland gave me a quote for transport and the first quote was higher than the cost of the insulation. They could see that was ridiculous, so made other enquiries about transport. The next quote was better and less than half the cost of the previous and was half as much again if I collected it from the transport company depot at Wetherill Park. So I collected it from Wetherill Park.

I had put some packs of insulation in the car before and thought I could fit three packs in, but the packs I had collected before were smaller and these were packs of 6 580 x 1200 batts.  I had the family with me as we stopped to pick up the insulation on the way down to Culburra. The lady at the transport company thought there was no way we could fit it all in and my family berated me for not bringing the trailer. So everything was emptied out of the car, my son's seat was moved to one side, and we fitted two packs of batts in the boot and one behind the passengers seat and the rest of our gear was stuffed in around the insulation. We were fortunate I could fit it all in, but lesson learnt when picking up insulation.

Once we had the insulation it was not a problem finishing the installation although one section where the front pavilion joins the main pavilion and all the water and gas pipes were was a little tricky and the insulation had to be slit and tucked around the pipes. The whole house in now insulated and it does make a noticeable difference to the temperature at night.

Work also continued on finding the right render colour. Our earlier render tests showed us that we would need to use some kind of cement colouring oxide to achieve the colour we were after. I went to South Coast Decorative Concrete Supplies hoping to get several different oxides to try out however they only sold the oxides in 9kg bags, which made it too expensive for me to get more than one bag. After much debate I chose Sundance from Concrete Colour Systems.

CCS Sundance oxide

I mixed up small batches of render using 1/20th of a bag of render mix and then divided this in half, making up a mix using 1%, 2% , 3% and 4% oxide. However I only had kitchen scales accurate to 1g to measure out the oxide and I was using such a small amount of oxide I was hard to get it accurate. I have since ordered a set of jewellery scales on E-bay that are accurate to 0.01g.

1% and 2% Sundance oxide when still wet next to the earlier render tests

I chose the Sundance colour as it had an orange tinge to it which I though would counteract the greenish tinge of the uncoloured render. However, the Sundance looked a bit more orange brown than we wanted. We are looking for a light warm yellow. So we bought a 500g jar of Yellow Builders brand oxide from the hardware store. That turned out way too yellow an still has a slight greenish tinge while wet. We then tried the 750g jar of Sandstone Builders brand oxide, although we have not yet seen it dry the test when wet looked too brown. The closest to the colour we wanted was the 2% Sundance so we did a further test of this on the hemp wall and on the MgO Board and will see how this looks when dry. The more accurate scales will allow us to do more accurate tests in the future.

Top row 4%, 3%, 1% and 2% Sundance all dry. Bottom row on MgO Board 2% Sundance, 2% and 1% Sandstone all wet

2% Yellow and 1% Sandstone both still wet in afternoon sunlight

2% Sandstone and 1% Yellow both still wet photographed with flash

Work has now stopped while we wait for the" blue marks on the plywood" situation. We hope to get building again soon.

Nelligen Hemp Studio

The ANZAC day public holiday meant there was an extra day to build, so what else do you do when you are half way through building a house, we went and helped a friend build her studio. Nicole is building a hemp walled studio at Nelligen on the NSW South Coast. Approved by Council it is the first hemp build in the Eurobodalla Council area.

Nicole helped us out with building our hemp walls, so we wanted to repay the favour and I was keen to see how the studio was going. Her studio is being built in a beautiful location in a hill in Nelligen, with swamp and river views to the east and mountain views to the west.

View of the swamp

View out western window to the mountains

Nicole's build is different to ours in many ways and it shows that hemp walls can adapt to different styles. Nicole is building on a half suspended concrete slab, with a beautiful stone wall on the lower side. Her hemp walls are 300mm thick, to provide extra insulation in the cooler climate. To achieve deep window reveals on the inside she offset her frame toward the outside. The frame uses 90 x 35mm studs set at 450mm centres combined with large section recycled wharf timbers around the glass on the north side and as exposed beams supporting the first floor.

North and East side of the studio

Recycled wharf timbers

Nicole put up large sections of form work on the outside, avoiding the need to regularly move the form work up in the steeper sides of the studio. 600mm sections of form work were put up on the inside.

Form work on the steeper Western side

The use of 300mm thick walls was both easier and more difficult. It was definitely easier to place and tamp the hemp as there was no difficulty getting your arms and tampers around noggins and window sills. Nicole requested that her framing company put the noggins all in the same line, unlike my offset noggins. Noggins all in one row was definitely easier so that rises of hemp could be finished at the same point.

The smaller 45mm gap between the form work and studs was not a problem and plastic pipe spacers were cut to fit and she attached the form work with bugle-head batten screws. On the inside however, the larger gap between the studs and the form work meant that Nicole could not get bugle batten screws long enough to cover this distance and had to attach blocks of wood to her studs to be able to use the bugle batten screws to attach the form work. To complicate matters further the frame for her window openings were not the same distance from the form work as the frame and required different spacers.

Spacers with extra blocks of wood

Different sized spacers with window frame in background

Nicole used fibro as permanent shuttering around her window openings. If I build again I would do this, but would use something breathable like magnesium oxide board. I chose not to use this method, although it was recommended, as I wanted to curve the edge of my window openings. Nicole found a better way to do this by stopping the permanent shuttering a little bit short  of the edge, still allowing the edge of the window openings to be curved.

Permanent shuttering around window

Unfortunately Nicole has had to use sheet bracing, due to the high wind rating of the site and the second storey. Concerned about how the hemp will key into this she has attached some axe shaped blocks of wood to the sheets to give the hemp something to key into.

Sheet bracing

Nicole used Alcor as her damp proof course and I think this was a better choice than the embossed polyethylene I used. The Alcor keeps its shape when bent and was easier to turn down and hold in place.

Alcor flashing neatly turned down

Nicole is mostly using hemp that has come from the Ashford and and is a finer chop than the hemp sourced from Ecofibre in the Hunter Valley. The more finely chopped hemp seems to mix easier and tamp down more evenly. The pieces in the Ashford hemp were also more consistent in size. Given the choice I would use the more finely chopped Ashford hemp. Nicole also had her hemp in pre measured bags which made mixing much quicker. Nicole used the same Australian Hemp masonry Company binder we did. One bag of hemp was used with one bag of binder. This was a real advantage in her build since the thicker walls used up the hemp mix much quicker and the person mixing had a hard time keeping up with those filling and tamping. Nicole borrowed our pan mixer and this works well for a small crew of workers but with the thicker walls and easier placement of the hemp a large crew of workers would need a bigger mixer to work efficiently.

Finer chop of hemp

Hemp and binder mix

Pre measured bags of hemp

The sand Nicole used was a brownish yellow, rather than the grey Shoalhaven river sand we used. This meant that her walls were a warmer sandy colour when wet, but they look like they will still be a grayish white when dry, albeit with a brownish yellow tinge.

Hemp wall a few days old

Placing hemp walls

Nicole made a chook house with hemp over 12 months ago. It has been left unrendered since this time. The wall is only showing a very small amount of weathering on the bottom of the wall. This is very good as although the wall does not face the prevailing weather it only has small eaves.

Hemp walled chook house

Small amount of weathering on exposed hemp wall

I am looking forward to helping Nicole again and seeing how her studio progresses.

Western walls

Hemp walls in the afternoon sun