In order for the sheets to be easily fixed to the purlins, as a rough guide they should be at least 50mm wide. When positioned, roof purlins should be spaced no further than 1.2 metres apart when using sheeting with a thickness of 0.7mm, and 1 metre when using 0.5mm sheeting.
Builders aren't bound by standard rafter spacing measurements. But they do tend to space rafters in one of several industry-standard increments, typically either 12, 16 or 24 inches apart.
Batten gauge = (length of slate-headlap)/2.
ROOFING BATTENSRoof battens are one of those frequently misunderstood and overlooked aspects of house construction. But roof battens perform some incredibly important structural functions to safeguard your roof. Roof battens: Provide a breathable space allowing any condensation to be eliminated.
Setting Out up the roof (Gauge)Measure the distance (A) from the first, eaves course batten to the top course batten. Divide this distance by the maximum tile gauge. Round the answer up to the nearest whole number (B) – this gives the number of tile courses required. Divide A by B to determine the actual batten gauge.
It is not necessary to nail every single tile to the battens. Every tile of the two rows at the eaves, those up the verges, and along the two rows of the ridge should be nailed, but beyond that it is only necessary to nail every fifth tile horizontally and every third tile as you move up the roof.
In some roofing options like tile roofing, battens are a must to ensure tiles are uniformly installed and excess overhangs which can invite water damage are not present. Batten roofing is a great option for re-roofing.
To fix a timber batten hold the batten into position on the wall, making sure it is level using a spirit level. Mark the wall with a pencil along the side of the batten. Take the batten down and drill a 5mm hole in the centre of the batten to push a screw through.
Traditionally, a minimum roof pitch of 20° was recommended in BS 5534, but modern tiles and slates have now been designed for applications as low as 15°.
The amount of slates you need per square metre (m2) depends on which slate size you're using. For example, if you're using a 20×10 slate (500mmx250mm), you will require 21 slate per m2. A 24×12 slate (600mmx300mm) demands only 13 slate per m2.
The general rule of thumb – and for this example we'll use the most common size of 500×250 or “20×10” – is for every 1 meter squared of roof, you need 21 slates.
Slate & Half SlatesAs a guide, a slate of 500 x 250 sizes uses a slate and half of 500 x 375. You would need 2.5 of these slate per linear metre. Therefore, if your rafter length was 4 linear meters, your calculation would be 4 x 2.5 = 10 Quantity slate & Half's.
Side lap gap – The gap between abutting slates should be between 1 – 5mm, most people these days quote 3mm, up to a maximum of 9mm for fibre cement slates.
The
costs set out below relate to a modest L-shaped bungalow with a
roof area of around 180m2 and with one valley, hip and ridge tiles, and a universal dry hip and ridge system.
Slates.
| Slates (3,547 slates @ £1.27 each) | £4,504.69 |
|---|
| – Labour (5 days) | £1,260.00 |
| Valley lead | £92.42 |
| – Labour | £36.12 |
| Nails and fixings | £81.18 |
How many roof tiles are in a standard roof?
| Type | Size | Square Metre Coverage |
|---|
| Marley Mendip | 420 x 330mm | 9.7 tiles per m² |
| Marley Modern | 420 x 330mm | 9.7 tiles per m² |
| Marley Plain | 267 x 168mm | 60 tiles per m² |
| Redland Plain | 266 x 165mm | 60 tiles per m² |
If you know the angle of the roof in degrees you can find the roof pitch by converting the angle in degrees to a slope, then finding the rise by multiplying the slope by 12. First, find the slope by finding the tangent of the degrees, e.g. slope = tan(degrees). Then multiply the slope by 12 to get the rise.
Failure of UnderlayWhilst roof tiles and slates are designed to keep out any rain, there is always the chance that strong winds can lead to rain forcing its way through any gaps or underneath the tiles.
For all roof areas and pitches, every tile should be mechanically fixed with at least nails, clips, or a combination of these options that provide adequate combined resistance to the wind uplift loads on the tiles. For roof pitches of 45° and above, each tile should be fixed with at least one nail.
Roof felt gives your roof a better appearance and will help it last longer. The felt helps ensure water drains off the roof after a storm. It helps keep your roof free from moisture, which can lead to leaks, rot, and mold. The felt also serves as a protective membrane against ice or snow dams.
The main purpose of roofing underlay is to reduce the effect of wind loading on the slate or tile roof covering, according to BS5534 – the Code of Practice for Slating and Tiling.
The original idea behind putting a dye into the battens' preservative treatment was to make “graded” battens stand out from the usual, “ungraded” ones (which usually look a bit green in colour, on account of the type of preservative used) and for that reason, the colouring process was originally very successful – with
Too much rain, snow, wind, or hailstorms will force the contractors to stop working until the weather clears. How Long Should A Roof Job Take? Generally, a roof job should take between 1 and 3 days.
Re: Roof without felt under the slates - do I need to strip the roof? The purpose of 'felt' is to provide a second line of defence against broken slates so provided the roof is kept in good repair it is not necessary. Nowadays a breather membrane is preferred to bituminous felt to reduce the risk of condensation.
Fasteners for clay tile roofs: clay tiles are secured to the roof deck using wire, special clips, concrete, ballast stones, or metal clips. Tiles are secured loosely - overly-tight wires or nails are likely to break the tile.
