I first discussed Stumbelbloc’s way back in March 2017 (our launch month), and that time I spoke about manufacturing them. Now I am talking about building with them as a business or offering a service using that as a building material what is known as “blockwork“. I will get into why I think it might be better in certain circumstances vs basic concrete blocks.
Blockwork is a construction technique using large concrete or cement blocks. They’re often much larger than a standard clay brick, but have a hollow centre to make them lighter and easier to work with, as well as improving their capacity for insulation. Blockwork is often used in construction projects because of its cost effectiveness and ease of use. – Solutions Built
Nomenclature
When I speak of “Stumbelbloc” I’m referring to an interlocking block for building (not paving). After all you could simply bypass the local guys and get moulds from Alibaba. I say this in the context of that many different building supplies have become somewhat genericized trademarks in South Africa (a successful brand name or trademark that has come to refer to the generic class of objects rather than the specific brand type). We have fibre cement boards (Nutec), magnesium oxide board (MagnaBoard), sheet metal Chromadek (which is Mittal Steel’s brand), plasterboard used as drywall (RhinoBoard). So when I say Stumbloc or interlocking block I am referring to the same thing. I am not going to be referring to it as “Stumbelbloc” as they are not paying me to advertise their product/brand.
WTF is Stumbelbloc again?
Stumbelbloc is a concrete block but the mould is designed as to make the blocks easily fit together (think lego) and thus easier and faster to build with.
…characterised by a tongue and groove mechanism that has the ability to hold the block in place hence requiring little to no mortar in between the blocks. They basically have protrusions that fit in the depressions on the next block – What you need to know about interlocking blocks
The business
This current business in Cape Town looks like this: teams of people who build using Stumbelbloc are linking up with (or referred by) people making the blocks, win-win. But the model is unique in that they are building fast and cheap. They sleep on-site and are able to build quite a bit a day. If you remember I have been musing on bringing down the cost of building quite a bit. Yes, these are foreigners building here and these guys their expenses will be lower than us locals as they live much thinner than us. But this is what I was talking about: we need to find a way to bring down the cost of building especially in the Cape Colony. You can build a mansion in Limpopo for what it cost to build a flatlet in Cape Town. Yes, interlocking blocks are often marketed allowing “everyman to build” but most people won’t know how to do it properly. Afterall look at the RDP houses built by cleaning-security-building tenderpreneurs, they can’t even build properly with basic concrete blocks and they are supposed to be “builders”. Hiring a team will be much faster and better to do a proper job. One of the advantages is that these blocks allow for fast construction due to the fact that one does not need to wait for mortar to dry to keep building.
You are able to build much faster using interlocking blocks as it does not come with the legacy problems of bricklaying in a city like Cape Town. One of the reasons for high costs and long time is inefficiency and to be blunt time-wasting. Go ask a guy standing outside Builders: “can you lay bricks”, “can you plaster”, “can you fly a plane” they just say yes to all as they are desperate for work. Even experienced builders, just watch them on site, they lay one brick, check if its level, lay other, check again. This is all time-wasting and designed to drag the job out for as long as possible. Any experienced builder will have developed muscle memory to build a wall straight without checking every minute. There are some caveats with building with interlocking blocks but none that are deal-breakers. I believe the biggest issue is that according to Stumbelbloc website it was only approved for single-storey dwellings in SA. Although my neighbour who is a professional builder tells me it is possible and has been done (and approved) multiples times (two, three and four stories) locally providing it is overseen and signed off by an engineer to make sure hackjobs building for single aren’t going double without approval (he spoke of “7 Megapascals (MPa) for single and 14 or 21 MPa for double then your foundation at the bottom is a bit bigger”). Which is backed up by this quote: “They are not safe to use as load bearing wall in highrise structures unless under the instruction of an engineer”. – source He also floated another alternative: MagnaBoard or Nutec at the top on the second storey.
A 42m2 “dream home” in Zimbabwe.
The business model
Now if you remember what I said last time? It is cheapest to simply cast the blocks yourself. That is still the case. However, people who do not want that hassle but still want to control things can buy the blocks and adhesive and then hire a business that offers this service (which is what I am talking about here). The business model is really simple: it is labour only. The client has to provide the blocks and the thin-bed mortar – Blockgrip [PDF] – the blocks are dipped in to be joined together. The business model is made up of only two parameters:
The price per labour (only) per m2/ blocks laid & and how much you can build per day. Now the 42m2 cottage they like to show can be built in 4-5 days. If you are charging R500m2 labour x 42 that is only R21000 for four to five days of work – that is cockroach money according to Cyril – and how many people? Remember Ramaphosa said R1 million-a-year members of parliament are struggling to make ends meet. That means if you charging cheap you need to ramp up building and build a pipeline of jobs. If you charge R500 a m2 and can build 50m2 a day then you looking at R25 000 per day. As you go from site to site. But the question is how many people do you need to build 50m2 per day? And that is your homework for today.
When mixed with water, BLOCK GRIP produces a workable mortar that generates, once cured, a high adhesive power between blocks.
Remember you need to have some building skills, as this is sometimes marketed as being idiot-proof. We are not in Europe where there is a good education system. You will also need to know how to lay a foundation. And I believe the foundation is best to be priced separately from the building. But that is just my thoughts.
