English Roofer Brittany

Not long ago, I built a new roof from scratch. This was my first roof and luckily it was for a play area, so if it leaked, nothing of value would be ruined. Most of the materials used were new except for the tiles which were reclaimed.

(Central Brittany Slate Roofing project - Play-barn) 

Having the opportunity of building this with both the clients understanding that this was my very first and having the trust in me to complete it was an honour. 

It was a project I always wanted to take on, especially using a traditional roofing material such as slate. I knew the principles of construction and have the skills with putting something of this size together, but nothing is as good as physically building.

Being an interior builder, I have the tools for cutting, shaping and nailing timber together. The only specialist items I had to use was a slate tile cutter and a proper roofing hammer.

(Slate Roofing Hammer & Cutter)

Building the timber frame isn't that dissimilar to building timber stud-work, there are rules to follow with regards to sizes of timber used as-well as the spacing between them.

Tiling is similar tiling a wall or floor, though using Tile hooks (crochets ardoise in French) for fixing not tile adhesive. One thing which isn't similar is the lapping of the tiles, his is something which is quick to learn though.

(Types of slate tile hooks)

Roofs in Brittany background basics

In Central Brittany, it's common to have black slate roofs built on stone walls. Properties are 40 to 50m2 per floor level and a roof of is usually at a 42 degree pitch and a surface area of 50 to 60m2. (And no they don’t follow the golden ratio – 1:1.62!)

The construction is simple. The ridge beam and purlins are generally set in the gable ends, the rafters are then nailed 90 degrees to the ridge and purlins (set 400mm apart, on the rafter centre). Then you have barge board 90 degrees to rafters, with a waterproof membrane (sarking felt) running 90degrees from the boards and tiles sit on top.

(Half Gable Roof in Central Brittany)

(Barge-boards nailed)

Tips and Tricks

Type of ladders - As you can see from the pictures, this roof is a half gable, IE the Ridge beam is against the gable end of the existing building. As such this makes a modern roofing ladder useless as you have nothing to catch onto.

I noticed that the local roofers used wooden Ladders and I quickly pick up the reason why. Using the crochets, you could attach the ladder.

NB There are two types of Crochets as well as many sizes - Crochet Point, you hammer the point into the barge board. Crochet Agrafe hooks over battons instead.

Tile sizes, and mapping out - There is not much to say about tile sizes, usually the size and type of material used depends of the available budget. I was using reclaimed slate tiles 200mm x 300mm, As such, I used 100mm long crochets as this allowed for a 3 overlaps of tiles. 

With regards to mapping out, I did very little in the way of chalk-lining. As the tiles are 300mm and the Crochets are 100mm, you'll generally stay straight and true, though do check once in a while.

 I did ensure that the horizontal and vertical of the timber frame did have a 90 degrees angle on the edges.  

Using the sarking as a guide - When buying sarking, you will notice that it is generally 1100mm in width, you are to overlap the ends 100mm (which the sarking has a printed line as a guide). If you set the guide line 90 degrees from the ridge/top plate or the verges then it becomes a great guide for the tiles.

(Sarking Felt overlay)

How to start off - You start from the bottom and work your way up. With a 300mm length tile I set a 100mm overhang at the bottom. To do this I measure 100mm up from bottom of the barge-board at either end and chalk-lined. Then 101mm parallel above the first line, I chalked again. (The 1mm allow for the 2.7mm thickness of the Crochet.) Repeat this 2 or 3 times and that should be enough.

The first run of tiles I turn 90 degrees and nail. (So the top of the tile lines up with the chalk-line and you have 100mm overhang.)
The second run sit direct on the first set of tiles, but now the correct way round. Both first and second set of tiles should be flush at the bottom and the top of the second run should line up with the second chalkline.

  

How to do your runs - There are two ways of doing your runs, either build up in pyramids of in straight line. I worked out if you laying tiles on your own, then doing straight line of 4 tiles per line, allow you to do 90/100 tiles an hour. If there are two of you, then the pyramid is faster.

(English Builder in Central Brittany - My first Roof)

Roofing tips by the English builder in Brittany

Of the Many Shapes of the Roof the gable will be Found Most Suitable for the Beginner. Marking Off the Wood for Cutting is Simplified by the Use of a Steel Square as Explained by Sparrow Legs Renovations.

THERE are various shapes of roof such as lean-to, gable, hip, hip and valley, gable and valley and Mansard.

For the average do-it-yourself man just starting on rafter cutting perhaps the gable roof is the most suitable. First, one should be familiar with the names of the different parts of a roof. Span is the overall width of building taken from outer edge of wall plates.

Run is the horizontal distance from wall plate to a point directly under ridge. This as a rule is one half of span.

Rise is the height of roof at centre of ridge (see Fig. 1).

The steepness of a roof is known as its pitch and pitches most commonly used are one-half, one-third, one-quarter and one-sixth. A roof with half pitch is half as high as the building is wide. If it is third pitch it is one-third as high as it is wide and so on.

Fig 1 - Diagram showing the various parts of the roof.

The Steel Square

A steel square enables you to mark off the various cuts and also to ascertain the length the rafter needs to be. The long arm of the square is called the blade and the shorter arm is called the tongue. The blade is 24in. long and the tongue 16 or 18in. The outer edge on one side of both blade and tongue is marked off in inches and twelfths of inches.

In using the square think of the blade as being the run of your roof, the tongue as being the rise and the hypotenuse (that is a line drawn from a point on the blade to a point on the tongue) as being the slope.

The measurements used on the square will be equal to one-twelfth that of the actual roof, i.e., inches and twelfths on the square will represent feet and inches on the roof. For an example let us say your building has a width (span) of 12ft. and you wish it to have a roof of one-third pitch. The rise will therefore be 4ft. (one-third of span) and the run 6ft. (half of span).

Lay the square on your timber so that the 4in. mark on the tongue and the 6in. mark on the blade is on the edge of timber. The tongue will now give you the bevel required for the top end of rafter-that is to fit the ridge board. This is known as a “plumb cut.” The blade will give the
 bevel to fit on the plate (“seat cut”).

Length of Rafter

The length of the rafter can be found by any of the following methods:-


1. Measure hypotenuse from 4in. mark on tongue to 6in. mark on blade and multiply by 12.
2. Slide the square on the timber twelve times keeping square on marks 6 on blade and 4 on the tongue.
3. Read off rafter length from rafter scale found on the  side of the square where the twelfths occur.

If method No. 2 is used it is made more easy to slide the square if two strips of wood are screwed together on the hypotenuse. Either method will give rafter length from the centre of the roof to the outer edge of the wall plate. Where a ridge board is used, deduct half thickness of the ridge board from the rafter length and add the allowance for overhang as a separate measurement.

Fig. 2 - A Steel rule showing the rafter scale which simplifies the task of marking off the wood.

Rafter Scale

Fig. 2 shows part of a rafter scale. The first column gives figures to be used in placing the square on the timber. In each a case in this scale 12 is the setting for the blade and the next figure is for the tongue.

Column 2 gives the pitch and the remaining columns give the rafter length. To use the scale for a roof of 12ft. span and one-third pitch select line 3 for one-third pitch and carry along to the column under the figure 6 (6ft. being the run of the roof).

Here you will read off 7-2-6 which means 7ft. 2 6/12in.

This will be the rafter length required and it is only necessary to deduct half thickness of the ridge board and add whatever is required for overhang.