Slating the Roof

Well the weather looks set to change, but at least the main roof structure is in place over the new extension and it’s time to get the covering on. It can’t be easy planning this sort of work never knowing quite what the weather is going to do, but these guys get stuck in and, as you’ll see, the new section is watertight in next to no time. As they say, planning is everything, and you can tell by the way various trades arrive on site at exactly the right time that G L Smith and Sons are pretty experienced with this. No sooner had the carpenter finished framing out the new roof than the roofers arrived to start on the slate covering.

The new sections of guttering have already been fixed and joined up to the existing guttering on the main roof. A pre formed plastic detail section seals between the bottom edge of the rafters, over the top of the fascias and into the edge of the guttering.

The roofing membrane is laid out horizontally across the rafters. Work starts with a strip across the bottom and this is tacked in position. Roof battens are then cut to length and fixed over this. The spacing of these battens is determined by the type of finish for the roof – in this case slates to match the main house.

It’s not long before the entire new roof has been covered with the membrane and all the battens fixed. The valley on one side of the roof where it joins the main house now has to be lined. This is done with sheet lead which is a pretty expensive material nowadays but probably still the best solution for this detail. The beauty of lead is that it can be readily formed or dressed to the shape required.

One section of lead is made up at a time. The long edges are folded back on themselves to provide a lip preventing rainwater getting back up underneath the slates. To do this, the lead is laid along a timber section with its edge overlapping an inch or so. A lead dresser is used to beat the lead over the edge of the timber to form a right angle. The lead is then turned over and the edge folded back on itself to form the lip. The tool used for this is known as a dresser – originally these were shaped wooden tools but plastic ones are commonly used nowadays.

The roofer lays this prepared section of lead in position at the bottom of the valley then dresses it so that it contours to the shape of the timber formers beneath. The end overhangs at the gutter and is dressed further to shape it so that rainwater is neatly discharged into the gutter. Further sections of lead are laid above this, each overlapping the previous a little, until the valley is fully dressed.

There are three guys working on this so it takes shape very quickly. Slates for the new roof have been stacked up on the battens ready to be laid. As many slates as possible have been salvaged from the main roof where the new section meets it. Slates are fairly brittle but a good number have been salvaged. As with the brickwork, reclaimed slates have been brought in to make up the deficit, and these will be mixed with the originals so that the whole roof blends in well with the original. The attention to details like this is what sets professional tradesmen apart from the rest. The knowledge and experience certainly shows with the team here.

Work starts on laying the slates from the bottom upwards. The first slate in each row overlaps the fascia board and plastic detail strip so that water shed from the roof will flow correctly into the gutters. The first section to be slated is where the old and new sections line up on the end elevation of roof. You will remember how the new ridge comes out at right angles a short way down the hip on the main roof – below this point, the old and new roofs meet as one elevation. Along the join, slates have to be lifted slightly to ‘weave’ in the new ones. Each course of slates is nailed in position with galvanized nails. Each row of slates overlaps the previous row by a little more than 50% - so there are two thicknesses of slate at any given point on the roof. The elevation meeting at the valley with the old roof is next to be covered. Again, the slates are laid in courses starting at the bottom and nailed in position as they go. At the junction with the valley, the slates are cut so that they line up with, and overhang, the lead work.

As the roofers reach the new hips, slates have to be cut at an angle to match the shape. This is done with a simple slate cutter which resembles a heavy duty snub nosed pair of scissors. Slates cut quite easily but care needs to be taken to trim to a neat line. These cut pieces are laid and nailed as the work progresses.

Once the slates have been laid, a row of ridge tiles is started. These are clay angled ridge tiles similar to those on the main house. Starting from the junction of the new ridge with the old roof, these are bedded on sand and cement mortar. A decent bed of mortar is run along the ridge then the tile set in place. The sides and joints are pointed up flush as they go.

Finally, the hip tiles are laid. Due to the angle of the roof along the hip, they fix a roof iron at the bottom of the hip first. This is a shaped metal bracket with a decorative loop on one end and serves to support the weight of the hip tiles so that they cannot slip down. Hey presto – roof finished ! Granted there were three guys on it but still not bad to have that all completed in little more than a day. The carpenter has been framing out the smaller sections of roof between at first floor level so we’ll be reporting on that next.

If you live in the Hertfordshire area and are looking for a professional building contractor, you can get in touch with G L Smith and Sons via their website: http://www.glsmithandsons.co.uk/