BROCHS - THINKING SCRIBBLES

There is something about scribbling that records thoughts that assist in sorting matters out. While one might ponder matters for hours, it is scribbling that documents ideas in another way, and allows them to prompt other concepts differently. One might call it ‘doodling’ in order to highlight the distance, dreaming, and discovery involved in the drawing process that is loose and revealing, searching in its own casual manner, becoming a stimulant for parallel visual interpretations that can inform other thinking processes.

The scribbled napkin.

Broch matters have been pondered for years – see:

https://voussoirs.blogspot.com/2017/02/brochs-more-ponderings-on-fragments.html

https://voussoirs.blogspot.com/2019/05/the-game-of-brochs.html

https://voussoirs.blogspot.com/2019/04/building-brochs.html

https://voussoirs.blogspot.com/2016/09/how-architecture-shapes-and-moulds.html

https://voussoirs.blogspot.com/2019/04/more-on-building-brochs-thinking-doodles.html

https://voussoirs.blogspot.com/2020/02/on-planning-meaning-mental-structures.html

 - but the questions still linger. Each step seems to raise more questions, that again lead to more scribbling. This process started the other day on the proverbial paper napkin, just because it was there; then the scribbles continued on the reverse side of the napkin until some A4 paper was pulled out to continue expanding on the thinking.#

The napkin sketches related to thoughts about the top of the broch: how was the broch finished off? Ideas on broch building have been recorded previously, with the broad acceptance that the Mousa parapet walkway might have been the way brochs were finished off. While Brian Smith of Shetland Archives has argued that the broch was never roofed, one has put the case for this being wrong, and has suggested how brochs might have been constructed as dry stone enclosures with timber framing inside. Roof or no roof, the matter of how the brochs were completed remains a question.

The more one thinks about the roof and the conditions in the broch, the more essential it is to be explicit about exactly how the broch might have been completed at the top. One knows that Mousa has undergone both destruction and reconstruction, so the current situation cannot be accepted as being the final solution.

When questions are raised about how moisture was managed in the brochs, both as rainwater and condensation, thoughts turn to air movement and detailing. Without air movement it is very likely that brochs would have become very moist and mouldy. Rain water could have easily been excluded, but it is condensation that becomes the problem with enclosed spaces housing animals and people. Even with a fire, the rock walls would be cool, condensing surfaces for airborne moisture that would become the perfect place for the unhealthy growth of mould. If the broch was used for important stores, then mould is the very last thing that one would want.

Drainage and ventilation?

The broch has been previously analysed as a cavity-walled structure similar to the cavity brick walls we have today, with ties sloping outwards to drain the water away from the dry inner wall. These inner walls have carefully formed openings in them that one could speculate might be for the promotion of air movement. The original brick cavity walls used to be vented internally to keep the inner wall dry. Might the cavity be part of a ventilation system that manages moisture and mould?

For this to be so, one might expect that there would have been a structured response to the idea externally at the top of the broch rather than allow on the usual leakage between the rocks for this important function. Such precision in the internal fabrication would seem to need some resolved completion of the concept externally. Might the top of the broch have had vents?

Then one has to ask about the Mousa model: why would the broch builders want to capture rainwater and snow and allow it to pour down into the cavity if the cavity was to keep the inner wall dry? Could there have been no external parapet? The blackhouse offers a prototype for both these options – openings and access without a parapet. Its external ledges on top of the earth-filled, twin exterior walls, are accessible for maintenance, and do allow water and snow to drain to the outside.

The blackhouse model.

The blackhouse model has an opening in the external wall that shows how vents could be formed. The sketches explore the possibilities that then raise the matter of the roof. With the roundhouse being the original model for the broch form, might one speculate that the broch was a staged construction where the roundhouse was lifted, and lifted again in order to accommodate more animals and stores? If this is so, then one could assume the broch roof was the roundhouse roof, even if it was not staged.

Might rocks have anchored the broch roof?

How was this roof supported? Such a roof would be difficult to support on dry stone walls. The windy conditions would suggest that there was a need for a roof that was carefully tied down. Resting structure on dry stone walling does nothing for holding anything down. One could speculate that the timber framing inside continued up as a core set of posts, with a perimeter structure doing likewise. Such an arrangement would allow some detailing for ventilation above the dry stone wall.

Roundhouse stages?

So the sketches continued. Why not have a blackhouse detail at the top of the broch? One might wonder about the security of anyone on this ledge if one considers the broch a defensive structure. So might there have been some castellated form of parapet like the Great Wall of China? This would offer some shelter from exposure to any attackers, and still allow water and snow to drain away to the outside, rather than load the cavity space.

Stair access?

One has to remember that the broch has the intramural stair. One would not want this space to become too wet, mouldy, and mossy, as it would make access dangerous. So the external drainage does make sense; but there is the exit. Most broch models ignore the fact that there is a stair, and make no allowance for any exit at the top of the broch. Given that the builders went to the trouble of providing this access, one has to assume that the exit at the top of the broch was resolved properly; that it was not an awkward hatch or an open void for water to flow into, and for snow to fill up.

What could have happened here? One could propose a sheltered exit area, but what might its form be? Here the sketches guess at possibilities, but they all look too crude. One has to assume some degree of sophistication in outcomes here; the broch has not been built by fools using an ad hoc process. It is not until one returns to the roundhouse concept that a solution arises. Using the raised roundhouse idea, one can postulate a roundhouse roof. Looking at these roofs, one sees a solution to the broch problem of exit: the roundhouse entry itself. The roof of the roundhouse is frequently shown as a thatched swelling that rises from snug, low edges to gain height at the doorway.

Sheltered access?

This model would suit the broch very well. The roof could generally be kept low to the dry stone inner wall until it came to the intramural stair exit, when it could swell up and extend over as a shelter. This would provide a raised portion of wall in the living area – the equivalent of the entry to the roundhouse. This section could become a main vent for the interior; and, with a ladder, provide direct access to the external walkway. Why should the top of a broch not be as inventive and organic as the remainder of the structure?

The roundhouse roof form?

The scribbles explore the options. Could any external vents in the dry stone walling be a part of the castellation forms; or might the openings have been framed by the profiling? The structural detailing seems better resolved by the latter. Still, one is left wondering: does the castellation concept look too much of a ‘castle’ cliché? Is the ‘blackhouse’ detailing preferred as a visual outcome? Why should we even have any preferences here? What causes us to bring these preconceived visions as judgements? Why are we questioning our logic?

There are more matters to test: could the parapets have had drainage outlets as well as ventilation slots? How might the stair exit be detailed with a ‘blackhouse’ edge? Did the stair always go to the roof ledge? Might it have had direct access into the living area? How much ‘restoration’ work did the Victorians undertake? One only has to refer to Maeshowe in the Orkneys to understand that the Victorians were never shy about reconstruction.

Is the castellation form a dry stone detail?

The scribbles will continue.

Alternative drainage, vent, and shelter?

#

NOTE

These thoughts and scribbles were developed while writing The Chinese Broch- Hakka Tulou: see -  

https://voussoirs.blogspot.com/2022/09/the-chinese-broch-hakka-tulou.html