Reuse and Recycling on Site

Many building products come wrapped in plastic and so like with all the other waste building materials we have accumulated on site I sorted and stored the plastic. My piles of scrap timber have been useful and some of it burnt in friends wood fires. Some of the metal pile, being meters and meters of metal strapping, have been taken down to the metal recyclers and other pieces like guttering offcuts sit there waiting for a use. The plastic has been very useful covering the door frames, windows and ceiling up while rendering. Bags from insulation have been useful for windows and ceiling. The long thin strips of plastic from the guttering was perfect for wrapping door frames. Plastic that wrapped other sections of roofing just fitted some of the windows. Even bubble wrap from some tiles bought mail order was used to protect the ceiling.

Windows and doors covered in reused insulation bags and guttering plastic

Insulation bags and bubble wrap protect the ceiling

Wrapped door frames

Front door covered in plastic

Small plastic bags from the guttering fittings were used to hold the measured out amounts of oxide for the render. We even piled up all the old binder bags, not sure what to do with them, but not ready to throw out something that may have a use. When I had a trailer load of sand for the render, I had to empty it out of the trailer. Rather than have to shovel it out of the trailer then measure out the amounts required for each render mix. I found that the old binder and render bags could comfortably fit the measured out sand and so to save double handling shovelled the sand straight out of the trailer and measured into the old binder bags ready for use.

Gutter fittings bags reused to hold coloured oxide

Binder bags reused to hold sand

Progress Made on Hemp Lime Rendering

We bought our pre mixed bags of render at the same time we bought the binder for the house. The lime render came with just a list ingredients to add and instructions to wet down the wall before applying the render. I had never used the AHMC render before I bought a pallet load of it for my house. I had done a brief bit of hemp lime rendering with Steve Allin at his workshop in St Ives in January 2012, but they used a different binder, very large hemp fibre and put on a layer almost 1 inch thick. This process was so different to that done at the St Ives workshop that it was of no use when it came to the hemp lime render we were using. My experiments to get the right colour and sand only gave me experience in doing 300mm square patches and even then the render sometimes went on really well and other times was really difficult.

Thankfully we had John our renderer to help us out, so these issues of getting the right mix and consistency were placed in his experienced hands. The first test wall John did, inside the wardrobe just in case things did not go well, was slow going but worked out fine. The next wall was faster but still quite slow. He quickly learnt that the hemp lime render does not spread easily across the wall, whether it is the hemp fines or some other reason, it is best to apply the render as close as possible to the location you want it and as close as possible to the finished thickness, then just use the float to smooth and even it out. The steel float gives a nice smooth finish, but the pieces of hemp and some of the large pieces of river sand ensure that the render maintains some texture.

The order of mixing using a standard cement mixer was ¼ bucket of water, ¼ of the 22.35kg bucket of river sand, ½ a bag of AHMC render mix, 80g of yellow oxide, the rest of the water and the rest of the sand and the rest of render mix. Mixing was a bit dusty but the holding of an empty bag over the mouth of the mixer after the render mix was added kept a little bit of the dust down. Later we changed this to using a bit less water and then adding a spray of water from the hose after the render mix went in and this kept the dust down.

The first part of the third wall went well then a slightly stiffer mix slowed John down substantially. He was not able to achieve the same finish as the first half of the wall, so he had to damp down the stiffer render, use a sponge float to work this water into the render then steel float it all again. Lesson learnt that there needs to be consistency in the amount of water in the mixes and the slightly sloppier mixes go on better. Achieving consistency in the wetness of the mixes is not as simple as using the same amount of water, as some buckets of river sand contain more or less water this needs to be adjusted for. So, like cooking it is about getting the look and feel of the mix right.

Front pavilion one day after rendering

Left wall fully dry and right wall 12 days after rendering

3 weeks after rendering

Wall freshly rendered

12 days after rendering

3 weeks after rendering

The weekend John worked on the third part of wall, my mate Tony was on site and having been to two hemp building workshops himself, he was keen to give hemp rendering a go. Tony and I got to work on one of the small MgO Board walls on the inside of the wardrobe. I used the stiffer mix and it was very slow going, in the confined space of the upper wardrobe it was awkward to trowel the render on, so I rubbed handfuls on the wall pushing them on until they were the right thickness then giving it a trowelled  finish. Given that John was at that time rectifying the effect of the stiffer mix Tony experimented with using a much wetter mix. The much wetter mix went on faster and could be put on with a trowel, however in parts it had difficult adhering to the wall. Going back several hours later to fix a patch where the wetter render had slumped a bit, a whole patch fell out. It appears that you need the “just right” mix, not too sloppy and not too stiff.  

The skinny wall done and patched by the non professionals

The following day John only had a couple of hours to spare and finished one of the walls with lots of windows. I used the “just right” render left over from John to patch the hole in the render on the side of the wardrobe. I had sloped the edges of the patch that had fallen out so there was less of a line where the join would be. Wetting down the edges of the patch and working the new render into the old, by making circles on the wall with my rubber gloved hand, the patch was filled and while it was not prefect  it was acceptable. John had also left a small join next to one of the doors and when he finished it the following day had to feather in the new mix.

With still more render mix left over I worked on the upper inside section of the wardrobe. A ridiculous section to render as no none will ever see it, but a good place to practise. I was painfully slow at rendering and it was very hard work on my arms, but the finished render was acceptable and was sticking to the MgO Board walls. Given the snail like speed of my progress I am glad to have outsourced the rendering.

We have applied self adhesive render mesh diagonally across the corners of the windows and along the joints between the hemp walls and the MgO walls as well as along the joins in the MgO Boards. I am using a 5mm mesh that comes in 200mm wide rolls from Foamex. The render mesh is to try to restrain any movement within and between walls to prevent cracking. Despite using the render mesh we did get some hairline cracks at the corners of the first window we did. Later window corners had either no cracks or only very small cracks.

Only a very fine crack at the corner of the window

No crack on the other corner of the window

We used 200mm x 300mm strips of render mesh across the corners of the windows, however had some adhesion problems and these sections of render had a tendency to pull away from the wall while they were still wet. These patches were identified and fixed while the render was still wet. The cause of the problem was hypothesised to be the hemp fibres in the render preventing the render from pushing through the 5mm grid in the render mesh and coming into contact with the wall. For further corners we tried halving the width of the render mesh to 100mm x 300mm across the corners of the windows and doors. This resolved the adhesion problem and when fully dry after about 4 weeks we will see if there is any cracking. The adhesion problem was not such a big issue at the corners where 200mm wide render mesh was run along the joints between the hemp and MgO walls, but here only 100mm wide on each wall was being rendered at each time. 

I had originally thought that we would need render mesh to cover the whole of the MgO Boards so that the render would adhere to it so I bought from Foamex (manufacturers of polystyrene walling and insulation systems) two rolls of 200mm wide mesh and two rolls of 1200mm wide mesh. I had believed that both widths were self adhesive, I checked the small rolls when i purchased them but the larger rolls were wrapped up and I just assumed they were the same. But, when I got them to site I found that the 1200mm rolls were not self adhesive. Going back and checking my original quote I found that the mistake was mine and the 200mm rolls were listed as self adhesive and the 1200mm were not. I confessed to my mistake and e-mailed Foamex asking if I could return or exchange the 1200mm rolls. As they were unopened and unused this was not a problem. I went back to their warehouse where I had originally picked up the mesh from and had no problems at all returning the 1200mm rolls, getting three more 200mm rolls and getting a refund for the difference. The fabulous service I received from Foamex could not be in more contrast to the problems I have had with the plywood. 

While I was off site John continued rendering, as rendering is his second job it had to fit in around work and family commitments. John did three walls of western bedroom in the back pavilion and a section of the external wall, before he was struck down by illness and forced to take a break. It was interesting to watch the process of the internal walls drying. For the first three days after they are done it is hard to see much visual evidence of drying, although you can feel the render firming up. After about a week the walls look unpleasantly patchy as different parts of the wall dry unevenly. Two weeks later the wall looks much more even and after three or four weeks the render is all dry and stops changing.

Back pavilion a few days after rendering

About a week after rendering

Right wall done later than left

Rendering our first external wall was good and bad. Without the ceiling and floor detail to worry about the rendering went quickly and we chose to have a slightly rougher texture on the outside. Problems arose when a chunk of hemp wall next to the window fell out. I had taken an angle grinder with a masonry blade on it to the walls and taken off the sharp corners around the corners and around the windows, so that I could get a nice curve around the window frames. However, I believe that this cutting off of the corner may have cracked a weak section and we will not have to try and patch the section with render. Next time we will try rendering around the window without cutting the corners off the hemp walls.

Detailing around the window

Rendering the external wall

Where a piece of the wall fell out

Window detail

External wall a week after rendering

Front Door and Roof to Wall Flashing

On the way down to site I stopped that the hardware store and met a friend at the hardware store. My front door was strapped to the roof racks of the car. She said to me "Are you going to put the front door in yourself?" "Yes" I replied and I did just that. My only previous door hanging experience was from a shed so I was a bit concerned about my lack of experience. My solution was to hand the door first then build the door jamb around it.

I bought the front door some months ago from The Door Shoppe at Richmond NSW. A shop that is only open on Saturdays and sells discounted, seconds and end of line doors. I finished the door with three coats of Cabots water based acrylic clear finish. Then installed the Lockwood Nexion all in one handle and lock. The instructions for the lock were easy to follow and this first part of the lock went in well. Next I used my sharp brand new chisel to cut out the housing for the hinges. It was worth buying a new chisel for the job as it made the work much easier.

I used Tassie Oak for the front door jamb as I had for the rest of the door jambs in the house. However Tassie Oak is variable in colour and the first batch I got was a medium warm brown colour similar to my window reveals, the next batch was a lighter brown but the timber I got for the front door was very light. The colour combination is not quite what I expected, now the door frame will be closer in colour to the rendered walls than to the door.

I measured the location of the hinges on the hinge side of the door jamb, remembering to leave a 5mm clearance at the bottom of the door, and chiseled out the housing for the hinges before I put the jamb up. Even taking into account the width of the jamb there was going to be way more room in the door space than the door and jamb could fill, so I attached a strip of 20mm to the hinge side of the door opening before I attached the jamb. After checking several times with the level the jamb went in easily and the door was able to swing on its hinges.

Hinge side jamb in place

Next came the closing jamb, where the only tricky park was finding timber the right width to use as blocking between the frame and jamb. Since the jamb on the lock side was much further out than on the hinge side I could not use the nail gun to attach it and resorted to some long screws. The top of the jamb was even further away from the frame and the long screws had difficulty going in, so this time I resorted to my favourite batten screws. The batten screw may have been a little bit too much as everything lines up neatly in the inside and I had tacked the top jamb to the side jambs with the bradder, but the batten screws were so strong that on the outside where the wedges I used to get the right distance for the blocking had not reached the screws bowed the outside edge of the top jamb up a little. Not a big problem as the door still close nicely and I got my 3mm gap between the door and the jamb right.

Lock side jamb in place

I then covered all my nails and crews and batten screws with the thinner pieces of the stops that were neatly attached with the bradder (fix out nailer). Disaster nearly struck when putting in the striker plate for the door lock. I snapped a screwdriver bit and the tip broke off in the screw while it was half way in. I could not get the broken bit of the screwdriver out of the head of the screw and could not get the screw out. The screw was stuck right where the tongue of the lock needed to go. Desperation called for invention and I got the thin disc on thee angle grinder and cut a new slit in the screw head. This now fitted a flat head screwdriver nicely. Not only did I get the screw out, after making the pilot hole bigger I was able to put the screw back in. I now have a nice lockable front door.

Finished front door

The damaged and fixed screw

Unexpectedly the scaffolding was still on site and I got a good close up look at the parapet flashing between the roof and the walls. The overflashing that covered the apron flashing had been cut into the hemp wall and attached with roofing screws. Under the upper windows it also left only a very small piece of wall about 25mm high that will make for some interesting rendering problems.

The overflashing was very close to the upper windows

Overflashing held to wall with roofing screws

Overflashing cut into hemp wall

Joint between clad section of wall and hemp wall