Rain Delay

Yesterday, it took us quite a bit of time to sort out the few things we had left unfinished from Tuesday. We ground off the sharp edges of our tamping tools, marked out the various details inside our wall cavity, finished installing our chamfers, built a chute, tested and fixed a few problems with the pan mixer, marked out all our buckets with the correct volumes of lime, stone and water according to our recipe and fixed the bend in our walers by installing spacers between opposite walers.

We then started building a 'training' wall where we ran everyone through each of their tasks. We also showed the crew how to tamp the soil to the correct hardness. We tested our Zimbabwean compaction testing tool, but at 2N/mm2 it leaves an impression on most of the test sites. However if it was set to 1.5N/mm2, I am confident it would not. Nevertheless, the depth of the indentation that it makes gives us a clear indication of the quality of the compaction and we will continue using it at the current setting. By the time we were ready with the main event, it was too late and therefore planned to start on it today.

But today looked something like this:


In fact, we had 40mm of rain during the day which meant that the postponement due to rain was likely to last well beyond the weekend. The weather report is not very promising and this is proving to be very frustrating.

Broken Tubes and False Starts?

Today was the final day of preparations for the rammed earth phase.

We assigned a crew to start sieving the large pile of sand and this seems to work fairly well. I was concerned that the aperture size of the sieve was too large (10mm) and instead of completely replacing the wire mesh, we overlaid it with another mesh of a different aperture. This reduces the quantity of large diameter stones and clay balls that make it through the sieve whilst the smaller sizes remain unaffected. Larger pieces still have a way to get through, but their options are significantly reduced.

Several coats of waterproofing have been painted on the stem walls. They are now ready for the rammed earth and the outstanding matter now is the endboards and custom sized forms. The endboards have been fabricated and we are waiting for the sealant to dry. The wet weather has arrived and we have to make doubly sure that the forms are resistant to water in the coming months.

Poen, our millwright made a tool to test the hardness of our compacted earth based on the Zimbabwean rammed earth standards. I thought it would take him a few days as it had a fairly low order of priority in the scheme of things but the novelty of the item seemed to capture his imagination and it was ready the same day. I have just calibrated it but am yet to be convinced of its effectiveness. The rammed earth immediately after ramming is still quite malleable and I do not see it withstanding a force of 2N per sq. mm until after it has cured - which is too late to test the level of compaction. But I'm sure we'll adapt it to our needs and in the end, will get a consistent level of compaction.

We have been anticipating the arrival of the solar panels and today they were delivered. It was a long wait but worth it in the end. It burnt having to pay more to transport the container from Durban to White River than from Shanghai to Durban but this is Africa.

The container was well packed but despite this, 47 of the vacuum tubes were broken. All of the broken units were placed at the top of the container and it seems that they were broken whilst loading them into the fairly confined space. The rest of the consignment seemed fine including the bulk of the vacuum tubes. The photovoltaic panels were in four boxes which were too heavy to pick up by hand so we had to open the boxes and carry them panel by panel into the storeroom. This and sorting out the broken vacuum tubes meant that we took a much longer than anticipated to offload the goods. However, at least it has been done and they are here. Now we just have to finish the building in order to put them to good use and as I have lots of spare tubes, the damaged items do not constitute a crisis.

The apprehension is building for tomorrow and I can see that unless everything is just perfect, we will delay the start until it is. The rammed earth phase is not difficult and we've done everything to make it painless and foolproof. But despite this, we are apprehensive. It's like jumping into a dark pool not knowing what lurks beneath the surface. Let's just hope there are no man-eating crabs.

Whoa!

We have cast all the columns and the last two are busy resting in their formwork until Monday when they will be exposed to the elements. They all look stunning and the finish is just perfect.Our plan was to start ramming the first wall on Monday morning but I have decided to play it safe. In casting the columns, we were busy manufacturing various sections that we needed as we went. How we did not make a bunch of mistakes is anyone's guess and there were a couple of close calls. The major lesson learnt is that every single thing needs to be checked twice before we accept it as correct. One corner column was nearly cast out of alignment because of our eagerness to get on with the job. So now we have set Monday aside to make all the bits and pieces we need to complete all of the walls. A key requirement is to print out the latest set of plans and to work from these - currently we are working from a variety of versions. Already over the weekend, I've discovered that the window openings as per the plan are smaller than the actual windows. So all openings now need to be made according to the actual window sizes and not to the architects drawing.

On Thursday we set up one section of formwork in preparation for the first rammed earth wall. We are working with perfectly level stem walls and columns which should by default make the rammed earth wall fairly plumb. In addition, each panel is screwed into the adjacent panel as shown on the right. Despite this, the panels at the top still bowed in. To prevent this, we have now made spacers to fit along the top of the panel sections which now means that we have 450mm spacers along all four planes. This has resulted in a very rigid structure and there is absolutely no chance of these walls being anything but plumb all round. So we have made our first list of things to do (playing it very safe) and Monday's tasks are as follows:

1. Paint on Damp Course - we're using a paint-on waterproofing membrane.
2. Make Rakes x 2 - these are to spread the rammed earth lifts
3. Make top spacing brackets x 9 (i.e. extra 6) - to prevent the forms from bowing in as per picture on the right.
4. Make seat for formtop operator - we are hand ramming the walls and this person will coordinate the soil delivery, the colour mixes and keep all the implements clean.
5. Step ladders for inside and outside of forms - for people to get in and out of the wall cavity.
6. Finish facebrick and concrete infill between pillar and brick course - this is the final thing that is done to the stem wall before we are ready to set the forms for the wall.
7. Build Chute x 1 - the bucket that will lift the mix is quite wide and we are going to build a chute to ensure all of the soil lands in the right spot and not all over the place. 300kg of soil landing on your head from 4m will do some serious damage.
8. Build base panel for the 925 wide x 2400 high window x 2 - this is a simple way for us to sort out the window ledges. Rather than making a complete volume displacement box, we are using a simpler method that gives us more flexibility, a better finish and a better braced endboard.
9. Build endboard panels for the 925 wide x 2400 high window x 2 - these are the vertical panels which will form the wall edge for the windows. Hopefully by spacing them the exact width of the windows and bracing them properly will make installing the windows a doddle.
10. Build base panel for the 1350 wide x 3600 high window x 4 - same as pt.8 above but for the wider window.
11. Build endboard panels for the 1350 wide x 3600 high window x 4 - same as pt.10 above but for the taller window (3.3m high)
12. Arrange small hand stamper - this is to get into the hard to reach places.
    
13. Purchase 45 deg plastic inserts: 12 x 3.6m - this is to create the chamfers on the walls. We hand made the ones for the columns but we are going to use off the shelf plastic ones for the rammed earth work.
14. Sort out Chalk Line - to mark the levels on the forms for the coloured lifts and endboards.
15. Purchase buckets for lime, stone and water - this is to ensure that we have a standard mix every time. The idea is to measure out the first few and then have a standard measure for each item, which will be a bucket with a mark on it that reads "Fill to here".
16. Submersible water pump - this we will use to pump a standard measure of water into the mix.
17. Permanent markers for drawing lines on shutterboard & for labelling buckets
18. Weigh all the lime that has been delivered & mark the bags - we've had bags of lime supplied and these are in different sized bags. We need to weigh them all so we are not paying for lime that has not been delivered.
19. Arrange plastic to to cover all rammed earth walls for a 5 day curing period.

Things to work out on Monday:

1. Define a set of safety rules - especially for the formtop operator.
   
2. Work out how to mark & install keyways where brick walls intersect rammed earth walls.
3. Work out how to mark & set out endboards (Volume displacement box) where windows are to be installed.
4. Work out a simple mechanism to load the correct amount of soil into the hopper according to the length of the wall. Note: The maximum finished 'lift' size - the height of the compacted layer is 12cm. The maximum uncompacted layer should therefore not be more than 15cm but I feel we should reduce this to 12cm. When putting in a coloured line, the lift should be 6-8 cm for a coloured line, preceded by a 6cm uncompacted natural lift to achieve the wavy (not straight) finish.

Coloured Seams: Coloured seams must be placed at the following heights above the stem wall:

1. 150mm Red
2. 850mm Red underneath/Black above
3. 1800mm Black
4. 3000mm Black

All seams must be made to look natural (i.e. no straight edges). This is achieved by sandwiching a coloured lift between un-compacted lifts of a different colour. Note that the surface of all lifts must be made uneven before the placement of the next lift. Compaction of the sandwich of lifts is then performed. Note: 1 kg of oxide per wheelbarrow of soil must be used.

Once all of this has been done, then we should have a set of formwork (excluding walers) that looks something like this:

And inside the form, it should look something like this:

And we'll all have to wait and see what the wall looks like.....

Double Height

Today we attempted to cast the tall columns - 3.5m in height. Each tall column uses three sections of shutterboard which makes it harder to set up. An additional issue is that the concrete vibrator does not reach the bottom of the structure when it is set up to its full height so the pouring of concrete also has to be done in stages i.e. set up section, pour and vibrate concrete, set up next section, pour and vibrate concrete. This raises issues of cold joints, misalignment of sections, or sections out of plumb and was again something we had not done before.

Our intention was to cast two columns today but before we could do that, we needed extra pipe clamps. The corner unit seems to swallow up all of our pipe clamps and we were effectively increasing it's height by a further 50%, which meant 50% more pipe clamps. In total we now have 70 pipe clamps on site. Also, to brace a tall column, we needed another tall column alongside it. This compelled us to set up and work two adjacent columns simultaneously which is what we managed to successfully complete today. And as a result, the site was a hive of activity.


The above gives an idea of today's progress. We were mixing concrete, cleaning and treating stripped sections of shutterboard for re-use, threading pipe for the additional pipe clamps, making new column shutterboard sections, preparing the stem wall for the rammed earth (to start on Monday) and erecting the top sections of the shutterboard - and of course pouring and vibrating concrete at each stage.

It was another very satisfying day. Tomorrow we hope to complete three more columns, Thursday another two and Friday the final two. Monday will see us begin the rammed earth part of the project. Hopefully Tuesday when we remove the shutterboard, will be a fantastic psychedelic trip induced by perfectly formed rammed earth walls freshly exposed to life. But we're getting ahead of ourselves again.

Up and Out

We're up and out of the ground. The stem walls have been finished, except for the final detail around the column bases. Four columns were poured yesterday after a few false starts which were due to some unforseen problems. However, in the end it worked out perfectly and we now think that the remainder should be quite simple but possibly time consuming to complete.

The first issue revolved around keeping the column alignment correct. The problem started when we wanted to vibrate the concrete, which creates forces that are quite surprising. The form wants to rise up and move around if not anchored correctly. In the end, we were helped by the fact that the forms we had made were slightly too short. As a result, we had to make a small extension at the base of each set to raise the main section up to the level of the stem wall. This allowed us to position just the short extension forms and when correctly aligned, we cast a key which would then prevent the whole form from moving around. Another advantage we discovered was the the stem walls (which have been built exactly the correct width of the wall and are perfectly aligned) provided an accurate anchor point for the column formwork. So the combination of the stem walls and the column key locked the base of the formwork into position that made the remainder of the exercise very simple.

The next issue was to sort out how to brace each set of column formwork as the inclination is to lean out of plumb. We ended up using the walers and pipe clamps and cross-braced between column boxes. We also used the pipe clamps to assemble each column box and despite having 51 pipe clamps, we could have easily made use of a dozen more. We tried screwing in bracing pieces, but when the concrete was being vibrated, even these began to show signs of being too weak. In the end, we just moved pipe clamps between one column and the next. It was only during times of vibration that this additional support was required and we found the pipe clamps and mini-waler combination to be the most effective bracing mechanism.

We set and cast the corner section today. This was much easier to do especially as the adjacent column was set plump and was something we could use to anchor the corner box. With all the pipe clamps and walers in place, the structure was exceptionally rigid. Especially after the experience gained during the previous day, we were much more confident about what we were doing and had more faith in our form work and its ability to withstand the concrete and vibration.

We precast holes for the pipe clamps into the columns. This will allow us to finish them off with a bit of plaster and the evidence of the holes will vanish under some paint or cladding. I decided that this was preferable to leaving holes in our rammed earth walls which could not be fixed without the evidence of the repair being visible for eternity. The benefit of this was significant. With precast pipe clamp holes, it took two pairs of hands to set the walers. Without holes to anchor the pipe clamps, it took four pairs of hands to anchor the walers and of course there was a time issue also.

In the end, it was slower than we anticipated but we are very pleased with the finish and the ease of assembly (and disassembly) of the formwork. Although we are not even half way through making the columns, our imagination has leapt ahead of the program and we are dreaming of perfectly finished rammed earth walls nicely keyed into the columns and stem wall. It's great when things go well and even your fantasies have a happy ending.

Video Slideshow

Pan Mixer & Conveyor

We used the pan mixer and conveyor for the first time today. The stem walls had been bricked up and backfilled. Last week, all the rubble and dried concrete that had accumulated in the stem wall cavity was arduously cleaned and removed in preparation for the final concrete pour which when complete, would signal the end of the foundation phase. And today we were hoping to make a small dent in this exercise. After moving the giraffe and conveyor early this morning, mixing only began around 10 am, which meant that we had lost part of the day before we had begun.




Johan was concerned that the pan mixer would not work that well and was naturally skeptical about today's result. He's used to traditional concrete mixers and was expecting the pan mixer to leak like a sieve. It didn't.

We loaded six wheelbarrows of sand stone and cement at a time and this took a couple of minutes to mix. The loading and unloading of the hopper probably took the longest time as it was all done by hand using wheelbarrows. We made a special chute that allows us to empty the pan mixer directly into a wheelbarrow whilst the hopper & lifting assembly remains connected. The other option is to empty it directly into the hopper which can then be lifted up over a 4m ledge, but since our work was at ground level we used the wheelbarrow option.

Well, it turned out to be one of those days where everything went well. The pan mixer worked fantastically. We were even able to use the conveyor to load the cement into the mixer although this proved to be very dusty. The stone seemed to be the only problem as it was scraped around the drum making the chalk on blackboard screech that jarred the nerves a bit. This will be fixed tomorrow as Deon will come and set the machine properly. However, we made rapid progress and managed to mix around 12 cubic metres of concrete by just after lunch which is more than we will need on any day when we are ramming the walls.

Johan came away very impressed and promises never to use a traditional concrete mixer again. I came away happy as it was one more costly experimental item that has worked out as planned. Now we just need to test the hoist under normal working conditions and if it works, then the whole giraffe can be accepted into the building fold.

Occupancy

The final bee hive was occupied yesterday!! A queen with taste and one that works on a Sunday!!

Forest Final and Imminence

All the trees have finally been planted and just in time for the rains. We've been watering quite intensively as I've been told that indigenous trees grow as fast as exotics do if they get lots of water. John believes the trees are 'happy' in their new home and I've been surprised by a few trees that have sprouted flowers. The sense of what is to come is positive and I almost find myself wishing away five years to hasten the point where they will have grown enough to become a real forest. In the meantime, bees have taken up residence in two of the three hives I installed in the avo trees. I'm just waiting for a wandering queen to take up residence in the third one and I'll be a happy hotelier with 100% occupancy. It is just a matter of time and I hope by Monday it will be occupied - especially as bees don't rest on Sunday's and that's as good a day as any to move in.

My Google weather gadget has been promising rain for the past week and today was briefly warning of snow (in the African bush- please!!), but all we've had is mist and low cloud. Neil has said that he hopes the rains come after Paul Kruger's birthday on 10 October, which will mean a wet summer. If they come before, it will be a dry one. And now it's a question of what is rain? A light dusting of rain came through on Friday night and hopefully this will not be enough to define a dry spell, but just enough to prompt all of my scattered legume seeds to start germinating. There's a race between them germinating and the guinea fowl eating them. I think the guinea fowl are winning. However, the well-watered Cowpea seeds that were planted around the trees have sprouted and are growing vigorously. I just hope that they will bring the promised nitrogen to the soil especially as they have been inoculated with the appropriate bacteria - just as Geoff Lawton instructed!!

On the house front, the progress has been held up by the fixers who were assembling the reinforcing for the columns. After a final heated exchange, they came and finished the work they were meant to complete weeks ago. Now we are busy making final adjustments to our shutters; drilling holes for the pipe clamps and applying a final coat of sealant to make them last a lifetime. Once the columns are cast, which will take a couple of weeks, we can begin with the fun part which is the rammed earth. Johan keeps reminding me that this is all new to him, as it is to everyone. His staff haven't a clue of what is to come - least of all the carpenter who has made all of the odd shaped forms for no obvious purpose. This all adds to the interest level and based on the anxiety levels of Johan, all of his staff know that they are about to share in something unique. I just hope they won't be disappointed.

The solar stuff is on the water on its way from China! It's due to arrive around the 13th October in Durban. I would imagine our bureaucracy will tie it up for a further two weeks and then it will be delivered. By the end of the month then, we should be expecting a delivery of solar hot water heaters and 8kVA of photovoltaic panels. The 'Justroof' solar panels when installed should look similar to the above picture. With the walls going up at around that time, it feels like we are imminently due to encounter a very steep, perhaps rocky but very exciting learning curve!

I've uploaded an updated house plan except the roof will now change. We've decided to use prestressed hollow concrete beams as shown on the left, so it will take us a day or two to get the roof on. There is very little cost differential and we reduce the build time by around 28 days.

In the meantime, the giraffe is standing patiently ready to begin the hard work that lies ahead. Her head is up which is a good sign and she is connected to the grid and her emergency stop works too!!