The famous Bruynzeel House

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Aart Bijl: Construction of Bruynzeel House

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Drawing of the house plan showing the two straight and curved contours of the ceiling above. This also shows the symmetrical form of the curved ceilings over the four portions of the roof defined by the two straight contours, which had a strong influence on the design of the house plan.
A model of the house during an earlier stage of design. All models of designs were made by ourselves, in our practice.
The model of the house as it would be seen from the road.
House with roof removed showing subdivision of the spaces below, and the horizontal tops to main subdivisions.
Earlier during the construction, Flip Green and I standing under the roof while the supporting scaffolding was being removed.
This is about the time Munnik Visser & Black became involved, taking over the job of supervising completion of construction. The board (left) shows the names of the parties involved, including the contractors. Van Wyk & Louw were the engineers I mentioned in my description. B L Williams was a very good local builder; I knew him from my student days working for Pahl.
A general view of the construction seen from the street side of the house. This gives a good view of one of the two feet that supports the roof. The time was shortly before we left for the UK, about March 1962, and Val in striped dress, together with friends can be seen near the scaffold tower.
View showing guest accommodation (near completion) with walkway to house.
Closer view of side to road.
'Builder's yard' on site, and the house showing the sweep of the Yellow-wood ceiling.
© Aart Bijl

Dear Rosie

About the background to the Bruynzeel House project.
Not long after I returned to our practice from a year away in the Netherlands the project started to happen. (1960/61) Being a young practice we felt the need to get experience in Europe, and set up a routine of one of us working in Europe each year, and it had been my turn. While I was away our practice did some work for Mr Hartman who, if I remember correctly, was connected with the Bruynzeel organisation. That is how we found ourselves one evening sitting in the Bruynzeel home, discussing the possibility of designing him a new house. Of course he was very big in timber, and a primary stipulation was that the design must exhibit his connection with timber. The work with Hartman had already got our practice designing timber houses, though they were of a far more modest kind.

We set about exploring the site Bruynzeel had purchased, and then considered our approach to the design. While I had been away our practise had already done some speculative work on timber hyperbolic paraboloid roofs for petrol stations, the Cape Town harbour entrance, and the like. We agreed that this concept could somehow be used for the Bruynzeel project. Lele Todeschini soon left for his year out, in Sweden. So most of my discussions during the design project were with Flip Green, and of course we discussed a lot.

I undertook a lot of investigation into this form of roof, for the size that would be required for a house. And I explored the possibilities of manipulating of its geometry to provide a reasonably calm interior to a house. What turned out to be striking about a hyperbolic paraboloid, apart from its overall shape over a square plan, was that any way you tilt it there will always be two straight horizontal lines at right angles to each other, and you can determine where they occur by controlling the amount of tilt. By having an unequal tilt I was able to use the horizontal lines to differentiate between large and small room spaces, and have horizontal tops to room dividers such as walls and cupboards. Each room space could then have a ceiling that showed a symmetrically curved portion of the hyperbolic paraboloid. You might say the Bruynzeel house was designed from the roof downwards, which is quite unusual.

From the point of view of construction, this kind of roof is quite easy to build. It requires only straight timbers for edge beams and joists. Its decking and ceiling consists of straight boards bending to the curvature produced by the assembly of joists. In the case of Bruynzeel's house, the decking was covered by copper sheeting, and the ceiling consisted of Yellow Wood boards. Where problems can occur is where the roof makes contact with supports from the ground.

I had a bit of trouble with the young Afrikaner engineers who were employed on the project. A hyperbolic parabolic roof has two corners that point to the sky and two that point to the ground. In theory the two that point to the ground can carry the full load of the roof, and that requires precise geometry of the steel shoes to fit the tilted corners and carry the load to the concrete feet. The engineers relied on calculations to make their drawings. When I saw the drawings, I studied them carefully and came to the conclusion that they were wrong. The engineers did not like that. I then used drawn geometry to determine what the shape of the steel shoes should be, including the unequal tilt of the edge beams of the roof. Not an easy task, and I had just come out of a spell in hospital. We then had an argument over whose shoes were right. I took the decision to proceed with my shoes.

When construction of the house was under way and the roof was up, Flip Green and I watched the scaffolding that was supporting the roof being removed. To express our confidence in my shoes, we both stood under the roof while this was happening. And the roof did not collapse!

In 1961 our practice became a casualty of the after effects of Sharpville, We had a large project, the design was complete, and working drawings were nearly complete, when the client withdrew the project. We understood this was brought about by lack of business confidence, and the client* refused to pay us any fees. We did not have the resources to challenge the client's decision and the fees due were a substantial amount in terms of our little practice. We decided we had to close our practice. Todeschini stayed in Sweden. Green went back to his home town, Johannesburg. I stayed in Cape Town, and found myself back in hospital fended off our creditors: we were men of straw. It was a macabre situation. See also Balgay Court in Kenilworth

During that time, that was when Munnik Visser & Black came onto the scene. The construction of the house was not yet completed and we invited them to take over supervision of the final stages. Bruynzeel agreed to this arrangement. Of course the design of the house had been completed, but there could have been some details that required some further designing. It was Arthur Black who took on this work, the person I think you described as claiming to have designed the house.

Yes I do know of Wilhelm Krüger, if he is the architect who designed the Meat Marketing Board building in Pretoria. He was one of the few really good architects around at that time, even highly respected by Pius Pahl.

Well think this is enough for now. Best wishes, Aart
20 October 2012

* I suggest the client pay up now and with interest!   Please contact Aart Bijl   
Rosemarie Breuer


Text by Aart Bijl, Oktober 2012 © Rosemarie Breuer