Posts Tagged ‘Roofing’

Green, green grass of home: Norwegian turf roofs

26/09/2012

For a moment, let’s leave aside the technical benefits (or otherwise) of green roofs, and just enjoy how they look in the landscape.

In an article for the forthcoming ESI.info Expert Guide on facades, roof finishes and rainwater management, director of the Future Cities project Austin Williams writes:

Green roofs are now lauded for their biodiversity, carbon neutrality, pollution-busting, happiness-inducing, rainfall attenuating, energy-saving goodness. Putting grass on a roof has evolved into a moral agenda that almost brooks no challenge … Specifiers need to be aware that green roofs are not a miracle cure.

This turf roof blends almost seamlessly into its hillside surroundings. Spot the chimney and small skylight on the left!

Needless to say, green roofs alone won’t meet all the challenges involved in creating a built environment that really works… Sometimes it’s good to view them from a purely aesthetic angle.

That is just what I did last August in Norway. On many of our walks during those two weeks, there were turf-roofed cabins round every corner – although because of their camouflage tops, we often did not spot them until we were right up close.

Most of the pictures in this blog post were taken at or around Herdalssetra, an isolated hill-farm that has been in continuous operation for over 300 years. The 30-odd buildings here are generally small, old timber shacks. Their turf roofs are simply a part of that vernacular and a reflection of which materials were most readily to hand at the time. However, we often saw green roofs in new-build housing developments in major cities like Oslo and Trondheim.

This post, then, is intended as a low-tech visual feast and nothing more. I hope it conveys some of the beauty of the Herdalen valley. Look at these pictures and imagine the bleating of goats, the crunching sound of fjord horses grazing in juicy pastures, the smell of sun-warmed juniper and dwarf birch, all to a backdrop rush of snow-melt waterfalls – and you’re half-way there!

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Norwegian stave churches: 1000 years old and still standing

11/09/2012

A stave church, or stavkirke, is a timber church with a structural framework of timber staves (beams) resting on timber sleepers and carrying timber wall plates. The wall frames are infilled with vertical planks.

Borgund stave church

The exterior varies from simple and rough-hewn to painstakingly ornate, and in size the churches range from small, shed-like structures – such as Haltdalen stavkirke – to the more imposing Heddal stavkirke, which is the largest of its kind still standing. (At the end of this post, you will find the legend of how the latter was built in only three days.*)

In medieval Norway, the stave frame was the prevalent construction method for churches. There were at least a thousand of them – some sources say as many as two thousand – the length and breadth of the country, built in the 12th and 13th centuries. But by 1650, most of them had disappeared. Following the devastation wrought by the Black Death, many churches fell into disrepair, whilst the Reformation brought a change in the construction, style and use of churches.

Tarred pine shingles clad the steep roof sections

Today, only 28 of the original stave churches remain. Set on stone foundations, the rest of the buildings are entirely made from wood; from the dowels to the roof shingles. It is amazing to see how well some of them have lasted.

The best preserved is Borgund stavkirke in the county of  Sogn og Fjordane, in which most of the existing structure consists of original timbers.

Built from pinewood between 1180 and 1200, it is a striking, darkly ornate structure at the heart of a lush valley. I took the pictures in this post when I visited Borgund last August.

From the interior. In places, rune inscriptions can still be seen.

The intricate carvings, small-format shingles, and black dragons’ heads craning their necks from projecting gable apexes, are miles away from the simple, neutral style we tend to associate with Scandinavian architecture.

Through the centuries, stave churches were preserved by covering the timber in tar. When I visited this summer, the church had just been freshly tarred, making the external wood even darker than normal and lending it a rich, warm scent in the sun.

The external gallery, freshly tarred

The magnificent detailing and impressive longevity of it all made me think of the immense contrast between the church itself and the bleak, sparse living conditions of the people who built it. For farmers and craftsmen eking out a living in a remote Norwegian valley, building such a structure must have been an immense undertaking.

Medieval carvings, beautifully preserved

* There is an old legend about the building of Heddal stave church.

A local farmer, Raud Rygi, wanted to have a new church built. A mysterious stranger came along and offered to do the impossible: to build the church in only three days. His fee for this task was one of three things: either the farmer would have to fetch him the sun and the moon out of the sky, hand him his own heart on a plate, or guess the stranger’s name. Unsurprisingly, Raud chose the third option. He thought he would have plenty of time for name-guessing, as surely nobody could build a church in three days…

However, on the first night, the materials were already in place. On the second night, the steeple was raised. Despairing, and with only one day left before the church would be complete, Raud wandered round the building site at dusk. Suddenly, he heard a haunting voice rising out of the mountain, singing a lullaby: “Hush now, little one, tomorrow Finn will bring you the moon, the sun, and Raud’s heart for you to play with…”

Riddle solved: the builder was Finn, the troll. Raud Rygi’s life was saved, and Heddal had its new stave church.

Runic inscriptions on a church wall

The Old King’s Road, leading up to Borgund stave church

Rainfall levels and siphonic roof drains

22/06/2012

BLÜCHER® was founded in 1965 and has since grown into one of Europe’s leading stainless steel drainage specialists. In this guest post, Frank Netherwood (Technical Manager from BLUCHER UK Ltd) explains the siphonic drainage principle and how it’s used in BLÜCHER products.

Frank Netherwood: Whilst a gravity system is simple to understand, the siphonic system is a little more complex … (more…)

Unseen, unused, unusual: roofscapes

15/06/2012

Think how much, in terms of sheer square metreage, of a city’s space is taken up by roofs. For such an essential building element – the sine qua non of even the most basic shelter – roofs are often unseen and unappreciated. In this post, I take a look at some unusual and appealing roof designs… and finish off with a fairytale for good measure.

Dutch roofscape

One of the more spectacular uses of a roofspace is to place a great, big infinity pool on top of it. This is what the septuagenarian architect and urban designer Moshe Safdie did on the Marina Bay Sands opulent hotel and casino in Singapore. The project is, apparently, the most expensive integrated resort property ever built.

The SkyPark pool, Marina Bay Sands (image by Eduardo MC on Flickr)

On a more modest scale, the Urban Sketchers blog “features sketches and often equally colorful stories behind the scenes by 100 invited artists/correspondents in more than 30 countries around the world. Some are architects and illustrators, others are graphic designers, web developers, painters or educators, all sharing the same passion for drawing on location.”

Beauty is sometimes hidden in unusual places. But if you look for it, it will definitely come up where you would not expect it to be. City roofs are a perfect setting for these findings.

In a previous post, we have summarised different types of green roofs as another way to make the roofspace work harder. Turf has been a traditional roof covering in Norway for thousands of years, and this Inhabitat post shows some good examples.

It was not unusual to keep livestock grazing on the roof either – serving the dual purpose of keeping the grass short and the animals fed. Occasionally, you can still see goats on green rooftops in Norway, as well as on the Old Country Market in Coombs, British Columbia, which makes a good trade from this curiosity.

From Hardanger, Norway (image by janticom on Flickr)

The practice was not without its dangers, though, as this old folk tale shows:

The husband who was to mind the house

Once upon a time, there was a man who was so bad-tempered and cross that he never thought his wife did anything right in the house. One evening, in the haymaking season, he came home, scolding and swearing. “Dear love, don’t be so angry” said his wife, “tomorrow let’s change jobs. I’ll go out and mow, and you can mind the house.” Yes, the husband thought that would do very well. So early the next morning, his wife took a scythe and went out into the hayfield with the mowers, whilst the man was to mind the house and do the work at home.

First of all he wanted to churn the butter (…) When he had churned a bit, he remembered that their milk cow was still shut up in the barn and hadn’t had a bit to eat or a drop to drink all morning, although the sun was high. It was too far to take her down to the meadow, so he thought he’d just get her up onto the roof, for it was a sod roof, and a fine crop of grass was growing there (…)

Now it was nearly dinner time, and he hadn’t even finished the butter yet, so he thought he’d best boil the porridge. He filled the pot with water and hung it over the fire. When he had done that, it occurred to him that the cow might fall off the roof and break her neck, so he climbed up onto the house to tie her up.

He tied one end of the rope around the cow’s neck, slipped the other end down the chimney, and tied it around his own leg. Then he had to hurry, for the water was boiling, and he still had to grind the oatmeal. He began to grind away; but while he was hard at it, the cow fell off the roof, dragging the man up the chimney by the rope. There he stuck fast. As for the cow, she hung halfway down the wall, swinging between heaven and earth, for she could neither get down nor up…

Don’t try this at home

Clay and concrete tile roofing: free design guides

07/06/2012

1. Concrete roof tiles guidance

I have come across some interesting design guides on Forticrete‘s website, free to download.

Re-roofing in a conservation area: Hardrow Glade concrete tiles at Friers Court, Wentworth, South Yorkshire

Forticrete is part of the Concrete Tile Manufacturer’s Association (CTMA) and therefore has access to a number of useful data sheets on various topics relating to the construction of roofs.

The association represents the interests of its members – Forticrete, Cemex, Monier, Marley Eternit and Sandtoft – who collectively produce an estimated 95% of concrete roof tiles in the UK.

The association supports the Roofing Industry Alliance, whose main aim is to increase the quality and reliability of roof construction.

Documents are available on the following topics:

  • Changes in rafter pitch
  • Dry fix ridges
  • Eaves detailing
  • Mortar bedded hips
  • Mortar bedded ridges
  • Party wall junctions
  • Side abutment detailing
  • Top edge abutment detailing
  • Valley detailing (parts 1–3)
  • Vent tiles and pipes
  • Verge detailing (parts 1 & 2)
  • Surevent: condensation control in roofs

2. Clay roof tiles guidance

The Clay Roof Tile Council has a technical library full of similar information. The CRTC collectively represents over 90% of UK clay roof tile production. Its members are Dreadnought, Marley Eternit, Keymer, Redland and Sandtoft.

Sandtoft Heritage Service clay roof tiles at the Reform Club, London

The Clay Roof Tile Council’s online library covers information on topics including:

  • Repair and maintenance
  • Design specification
  • Material specifications
  • Health and safety
  • Handmade technologies
  • Machine made technologies
  • Wind uplift calculations
  • Quality control
  • …and a very handy little glossary of terms.

Selecting and specifying roof tiles

On ESI.info, you can find, compare and select roof tiles in concrete, clay, slate, natural stone, fibre cement and zinc. You can also find timber shingles and shakes.

Search results can be filtered using parameters like roof pitch, tile type, manufacturing process, installation method and product accreditation. Why not have a go – and tell me whether you found the site easy to use?