Thursday, 28 March 2013

A good roof overhead ~ part 4 ~ a hiatus and a look at other roofs, chimneys and flashings

Note: Due to the popularity of this article I have expanded existing content and also added a new section about asbestos roofing.  Enjoy!
4th January 2014.

...In the previous article I wrote about the challenges faced by our neighbour John, with the design of flashing around their brick chimney: the chimney emerges from the first level of roofing, then butts against the side of the upper level of the house, and finally interrupts the guttering as it rises up above the top roof.  Both levels needed to be flashed, but differently.  How best to do this became a vexed question which took some time to work out.  At the right you can see a photograph taken when work on it was nearing completion. 

All this prompted me to look more closely at what other people had done with their roofs, and to go out, camera in hand, and to photograph a selection of them.  Here they are:

This elegant house has a slate roof.  In accordance with that style the ridging is formed from metal which features brackets across it at regular intervals:

The brackets over the ridging can be seen more clearly in the image below, especially in the lower right hand corner.  Note the treatment around the base of the chimney which shows a series of steps in brick-sized steps which would correspond with the bricks in the chimney itself:

All those angles in the different faces of that roof must have made it a substantial job, and a costly one! 

The more modestly sized dwelling shown below has a corrugated iron roof, galvanised iron being the most common roofing material used in this country.  There are plenty of challenging angles in it!  The flashing around the foot of the handsome chimney corresponds with the colour of the roof.  Note the finial on the peak of the roof just beyond the chimney. 

The corrugated iron roof of this house is simple and straightforward.  It's a relatively cheap roofing material to put on, maintain and replace:

In the next image we have a tiled roof which has its ridges formed from sections of material which match the tiles.  In this instance the flashing at the base of the chimney corresponds the paintwork of the chimney. 

The buildings below also have tiled roofs, with the cladding of the one at the left being formed from stucco.  The ridging has a segmented appearance due to the use of ridging tiles traditional to that style of roofing.  The little roof over the gate is an anomaly: it has been shingled and is of a different style altogether, so may be a remnant of an earlier building on the site, or may have originated elsewhere.  The style looks earlier to me than that of the main building.

The eye-catching building with the orange tiled roof shown below, is the old post office in the Dunedin suburb of Roslyn.  It is considerably older than the tiled buildings above as can be established by the sash windows alone.  Its roofing tells us more: the colour of the roof is of the terracotta tiles themselves.  The tiles used in early roofs of this sort were imported from France, and were costly.  A New Zealand company began manufacturing them in 1924 which enabled them to be obtained more cheaply, after which they became fairly commonly used.  Although they continued to be imported from France until 1929 this stopped in 1930 when new importing laws were introduced.  You can read more about them here:
  • Marseilles tiles - an article on the website of Te Ara, the New Zealand encyclopaedia.
What really sets this roof apart, and makes it clear that its tiles came from France, are the terracotta finials on the ridge tiles, three of which you can see below.  These were never made in New Zealand.

The terracotta finials can be seen more clearly in the enlargement below.  Note too, the ornamentation along the two main sections of ridging.  As soon as I noticed these I wanted to get up there and have a closer look!  The pole mounted on the neighbouring dome is a flag pole, which used to be a feature of our post office buildings.  

I can't move on from these two photographs without exclaiming over the ugliness of the street setting of this grand old building.  What a mess those other buildings next to it look - just awful, and all the more obviously due to the contrast shown here.  To my continuing disappointment lots of New Zealand commercial buildings are similarly dismal in appearance...  In comparison, this elegant building looks effortlessly and timelessly stylish.

This tiled house has its own quiet elegance:

And now to the sublime: this striking building stands on High Street near the centre of Dunedin.  The roofing material is slate.  I have it on good authority that the dark slate is from Wales and the pale slate is from the Otepopo quarry, near the township of Oamaru, which is about 110 kilometres north of Dunedin.  The ridging is metal, I have no idea what kind.  What beautiful finials it has!  It must also be said that its neighbours look worthy of it!

At this point I find myself compelled to take a little diversion into the history of the Otepopo slate quarry, which it seems may have been the only quarry of its kind that this country has ever had.  A report written by provincial geologist F.A. Hutton in 1875 gives a description of the slate here:
Further to this a fascinating news article published in the Otago Daily Times in 1878 provides this detailed description of what the quarry was like:
And this one from the North Otago Times, also published in 1878, tells a story of a very different side of the operation, of dispute over land used by the quarry:
This quote from a document held by the Dunedin City Council, explains why the slate from Otepopo was never able to compete commercially with Welsh slate:
"The story is often told that Otepopo roofing slate from near Herbert in North Otago could not compete in the Dunedin market with imported Welsh slate from the other side of the world, because the latter came as ballast on ships directly to the town." 
Slate roofs with tiled ridgings are unusual in New Zealand, but I've been told that this style is fairly common in Europe.  In the roof shown below the contrasting combination of the two is handsome:

I turned the lens of my camera a degree further to take in the neighbouring houses.  What a mix of styles those roofs are!  The one at the right has rows of corbels under the edge of the roof.  Historically corbels have been an integral part of the buildings structural support, whereas these are purely decorative.  They must have added quite considerably to the expense of the construction, but certainly give the building a distinguished appearance:

Asbestos roofing materials must not be overlooked.  Although this material is no longer used in construction it has been popular in the past.  The huge difficulty with asbestos is that with fracture and with aging its fibres can become free and present serious health and environmental hazards, so it is important to be able to identify the forms that it takes.  In New Zealand any handling requires skilled and certified operators who take special protective and disposal measures.  You can read about that via these links:
This site provides a very useful set of photographs for visual identification:
There are not many of these roofs in Dunedin these days, but with help I managed to find three, one of a corrugated material and the other two of tiles.  These are unusual in appearance and distinctly different from other materials.  The Asbestos Advisor site linked to above shows two more forms of tiles which resemble slate and shingles.

The building on the right is roofed with corrugated asbestos.  The green roof is is painted corrugated iron.

Here is a detail of the asbestos roofing:

The house shown below has asbestos tiles.  The whole building is so dilapitated that it looks in need of demolition, but to do so would be a major understaking, which may be why it has been left as it is:

This imposing house, built in 1914 by master mason, Henry S Bingham, has similarly shaped asbestos tiles, which must have seemed like an ideal material at the time:

The plaque on the side of the building gives some details:

Here is a closer look at the asbestos roofing tiles.  There are lots of different angles for the roofers to have worked out.  Some of the tiles have come loose.  Repairs are likely to be considered hazardous so they will probably be left as they are for as long as possible.  Even getting up there would be to risk causing more damage. 

And finally, after all this complexity, we come to the mind-bogglingly simple: a little house I used to live in which I refer to as the Dome house:  What sort of roof is that, you ask?  It is a complete departure from the styles and construction methods shown above...

I was told that the basic shape of the house was formed over an inflated balloon, which was first sprayed with polystyrene, and then with ferro cement.  I have no idea what form of reinforcing it had, if any, but I can tell you that it was strong enough to be climbed on and jumped about on.  I was a tenant there, so could not interfere with the building to verify the composition of the structure; if I had owned it I would have taken a 'core' sample! 

Below you can see how the windows were set into the sides of the building.  At the base of that structure you can see the only guttering of the whole building: simple halves of terracotta piping!  The only flashing, if you could call it such, was simple metal strips set slant-wise into the edge of the roof line above the windows, which deflected rainwater so that it ran down the sides of the building rather than straight down over the windows. 

The interior also deserves a mention: it was plastered throughout - very skilfully: try as I might I could never see any joins in the beautifully hand-wrought plaster swirls.  You can't see the swirls here but its light airiness, on the sunny side anyway, is evident. 

I have been told that these dome houses were exceedingly cheap to build which I am sure would have been the case.  Although the execution of design and much of the detail was poorly worked out, I like the concept and think it deserves wide consideration as an alternative to the complexity and vast expense of modern housing.

Coming back to our neighbours roof, the roofing material is tiles made of synthetic resin, manufactured to look like slate, but much lighter and easier to work with, etc.  In this country the style of slate roofs is for them to have metal ridging as you can see in the selection above, which is why John chose to apply stainless steel ridging rather than ridge tiles which matched the material and appearance of the supposed slate.  In other cultures different styles prevail.

Readers can click through to other articles about this project via these links:

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