Blackhouses are dry stone houses with thatched roofs, vaguely similar to the Welsh long house, although generally lower and usually without a gable, ie "hip ended" as shown below. They are long and thin, only one room wide. Externally they are generally around 6m wide and anything up to 3 times as long.
Distributed throughout the highlands and islands they were still in use in the Outer Hebrides relatively recently (mid 1970s), with the island of Lewis/Harris in effect their modern stronghold. There are of course regional variations in type however subtle, even between those on Lewis and Harris.
Fenton in "The Island Blackhouse" says that western Lewis Blackhouses of the late 19th Century had a parallel barn as shown (below), earlier they would have had maybe a third parallel row of buildings, with the central row being the accommodation and byre.
The name "Blackhouse", however, doesn't come from the muggy black atmosphere of the peat smoke, or because of the lack of windows. It could conceivably result from the fact that "the Gaelic for thatch is 'Tughadh' while black is 'dubh'. It is sometimes suggested that said quickly these two words could sound very similar and so the proper 'thatched house' could easily become 'black house'" (www.minchviews.blogspot.com). The more likely explanation is that the second half of the nineteenth century saw he introduction of thinner lime mortared walls in house construction on the islands. These usually lime-washed houses became known as "white houses" and the older traditional houses became blackhouses almost by default.
The walls are generally no more than 5 or 6 feet high and usually as wide as they are tall. The fill includes soil/peat to provide added protection from the wind and cold. "Later examples... were built with an external batter that gave a top width of 1.1m" (Fenton p27). The walls had niches built into them for storage, and sometimes these were large enough to sleep in (normally only in older blackhouses).
The ends/corners are usually rounded. It is usually said that this is somehow due to the wind. The curved ends of the thatch would undoubtedly give added stability in high winds, as well as being a practical approach to basic construction (i.e. it would be hard to do corners). To me it seems likely that the shape of the walls mirror the roof rather than vice versa, the shape can do little to aid stability in the wind. There is also the practical consideration that rounded ends do not require quoins. Neil explains "the stone is so damned hard to dress in to right angles, hence what ever little right angled stone [is used] for doors and windows". He also related a local folklore that suggests they are rounded since the Devil can't hide around a round corner. This said there are examples where the walls have right-angled corners whilst the roof remains rounded. This occurs most notably where there is a ledge around the top of the wall.
Historic Scotland reconstructed No 42 Arnol on Lewis, in the early 1970s. Now a museum, it is the main subject of Fenton`s booklet . Pre restoration photos of the same dwelling from the 60s clearly show such a ledge.
Photos of several of the restored blackhouses of the "blackhouse village" Gearrannan (Garenin) on Lewis show similar if less pronounced ledges than the one at Arnol .(www.undiscoveredscotland.co.uk/lewis/gearrannan/index.html) Since 1989 Urras nan Gearrannan (the Garenin Trust) has been painstakingly restoring the once derelict blackhouses essentially as tourist accomodation (the interiors have been modernised) and a museum. The photos show some blackhouses with gables.
Fenton suggests the ledge served a double purpose partly facilitating thatch removal/repair, (traditionally the thatch was removed annually and used as a fertiliser, the smoke saturation having increased its ammonia content.) More interestingly he argues that "water shed from the roof percolates through the core, helping to improve its insulating qualities in relation to both cold and wind" (p.11) (How this works with "wall beds" is not made clear). Whilst the idea of allowing walls to be damp might seem counter intuitive it is not a mythical isolated idea. Sally Hodgson (Derbyshire professional and DSWA member) studied dry stone houses built in South West Norway in the early 1990s, as part of a Churchill Fellowship. She confirms "the roofs I saw finished in line with wall middle to allow moisture to trickle through the packing in the cavity and the wall open to the weather the stones tilt slightly outwards to shed water, and there are no gutters of course. In the cavity are balls of peat and moss are kept swollen with moisture hence acting as a draught excluder." Neil suggests that even those without ledges have balls of moss and peat within the walls which would be kept moist through penetration of wind blown rain (the severity of which on Harris I am led to believe, has to be experienced to be believed). Despite the driving rain and the rough nature of construction (Neil points out this is due to the nature of the stone and the lack of modern tools, adding "I 'm not saying that they didn't have tools but they were great believers in using what you had available with minimum fuss"), Neil suggests that there would have been little damp penetration to the interior given the vast thickness of the walls coupled with the fact that the peat fire was traditionally kept on 24 hours a day.
Being a modern structure building regulations came into play with the Scaristavore Blackhouse. Here the walls were nearly 4 feet thick without peat,or soil. Instead they incorporated Tyvec, a commonly used building material to allow air to travel through, yet no water, normally used as the "felt" under roofing slates. Neil explains "this was integrated through out the centre of the walls on two sides. The other two walls , we used visqueen lining, a heavy duty plastic which would keep out moisture [normally used as an under floor damp proof course]. It was thought to use this on all 4 walls would cause a certain amount of condensation, hence the use of Tyvec."
The Scandanavian connection does not necessarily end with peat in the walls. There are several references to blackhouses having originated from the Vikings and being based on the Viking longhouse. Now these have many known variations, some of which even included stone (they are essentially wooden and hence in no way rounded). However they were inevitably "aisled" i.e rooms either side of a central corridor. I suppose that as their name suggests they are essentially rectangular, as are blackhouses, a lozenge is after all essentially rectangular. Personally I'm still to be convinced.
Building regulations or their equivalent seems to have always afflicted the blackhouse. Landowners frequently tried to impose modernisation with varying degrees of success, such as creating divisions between house and byre, separating living and sleeping rooms, incorporating windows etc.. Fenton points out that in 1893 the Lewis District Committee required the separation of house and byre by a wall with no internal communication yet by 1947 an estimated 40% of Lewis blackhouses were still of the traditional layout. In addition there were constraints against stripping the roof and the introduction of chimneys.
The Scaristavore Blackhouse given modern regulations had to have a chimney, unavoidable if you're going to have a fire but I feel somehow detracting from the aesthetic flow of the Blackhouse shape. It is however dry stone and its exact construction interested me so I asked Neil who explains "The chimney was built dry and built as we call it a Bell shaped gable to add strength to the prevailing S.W. Winds and rain coming in from the Atlantic. Within the chimney stonework we had a Isokern flue liner which was surrounded by mica. The Isokern flue liners were in 2 feet lengths and had male and female ends to give a secure fit and added strength to the flue, plus making it all fire proof." Fire regulations meant it had to project 2 feet above the rye thatch, which was treated, with a fire retardant. The stove the chimney serves is used for cooking as well as heating, runs on peat logs and coal. It sits on a large slate roughly 5 feet by 3 feet and had the name of everyone involved in the major build of the house, engraved on it. A nice touch.
As a final thought No.42 Arno has a series of 4 protruding slabs, similar to a step stile, built into one wall to enable access to the ledge. There is a good photo in the booklet, and one of the ledge pre-restoration. I would have loved to have shown them here but the nice people at Historic Scotland wanted around £100 for reproduction rights tripling the current print-run's production costs.
Thanks to Sally and Neil for their patience and help.
References "The Island Blackhouse", R.Fenton, Historic Scotland. 1995