More Roof basics – Plan and elevation of the previous roof.

In standard construction, the overhang at the gable (say 450) is usually not as much as it can be at the eaves (900 to 1200 typical), so the gable overhang cannot provide the same protection to the walls and openings in them that a hip roof can. The reason for this is that the rafters or truss members are heavier construction, and so can overhang more than the usually lighter roof purlins.

Dutch gables are as with many things a compromise, I quite like them and have done a few. A bit more work than either a hip or a gable but I like the looks of them. They also give a convenient place to put in a louvred vent.

Gable roofs have one advantage over the hip, and it is a good one for us guys, but not necessarily important for the house owner. More room and better access inside the roof space from one end to the other.

I was once building an addition to an existing house and the owner said that he was going into the roof space to run an electrical wire. After half an hour or so I realised that we had not heard him for a while. We found him semi-conscious, overcome by the heat. We had to carry/drag him about 12m to the manhole. We were very happy that he was at a gable end, and not wedged under a hip.

It is quite common to nail a board or a few boards, say 200 x 25, along the top of the ceiling joists or truss bottom chords to make it easier to move around in a roof space. This is very small detail, and it is often overlooked, but just ask an electrician who spends a lot of time in roof spaces whether he thinks it’s worthwhile.

Squillion Roof, Shed Roof

Here is an small room addition to a standard rectangular plan, and rather than try to keep the ceiling height the same as the rest of the house, which would make more work, we let the roof continue at the same pitch. We call This a scallion roof. It is a very economical way of roofing over an odd part sticking out from the main building.

gable roof and scallion roof

Roof basics – One version of a skillion roof.

This of course it has its drawbacks. It will not work too well if the pitch is very steep. The ceiling height gets too low. I have seen this done often for rooms like bathrooms and kitchens. Say we are using a main ceiling height of 2700 (9ft) in the house, the bottom end of the skillion could only be say 2200. That could be a bit of a no, because our minimum ceiling height is 2400. But the good news is that in cases of say kitchens and bathrooms we can average the ceiling height. The average between 2700 and 2200 is 2450, so we are OK in this example, if we line the ceiling on the slope.

The name skillion is more commonly used when referring to a plain roof with just a single slope, that is no ridge. I tend to call this a shed roof, with a skillion being either as drawn above, or any small separate addition to a main roof.

As with most terms in building there is a wide variety of regional differences in naming roof parts and types.

modern skillion roofs

Roof basics – Modern skillion roofs.

Architects are again looking at the humble skillion, and giving it a modern look, that has more to do with style and design, rather than simplicity and low cost of traditional skillion or shed roofs.

Traditional Timber Pitched Roof

At the time I started out in the game it would be safe to say that almost all house roofs were timber construction.

They were cut and pitched on site, and the roofing carpenter was king.

The carpenter did his own calculations from the basics of the design on the drawings. He was given the floor plan, a few elevations and the pitch or angle of the roof. He worked out the rest on site.

The timbers were heavy, which means costly, and the structural strength of the roof was only as good as the guys that built it. To pitch a large traditional style roof is also very labour intensive. I have not seen any traditional style roofs done for years, but at the same time there are still small additions and extensions being built, particularly in remote locations, were a roof built up out of individual pieces of timber is still the most cost effective way to go.

Traditional timber framed house roof