A. When the roof pitch is 35 degrees and above, or when the building is 10 metres wide or more, then BS 5250 recommends the use of ridge ventilation combined with eaves ventilation. This actually provides a much more efficient system because air passing over the ridge will draw fresh air into the eaves.
When there is just eaves ventilation there needs to be enough wind to force air in through one side of the building and out through the other.

A. Dry fix systems offer a number of advantages over the traditional method of mortar bedding. These include:

• Allows all-weather laying and fixing.
• Essentially maintenance-free.
• Overcomes problems associated with mortar such as cracking and loss of ridges in high winds.
• Provides full mechanical fixing of all components to resist highest wind speeds ever likely to occur.
• Provides continuous ventilation at the ridge - this is particularly useful in many modern buildings where the use of insulation between or above the rafter precludes the use of traditional ridge vents.
• Provides a consistent attractive finish.

A. The revised British Standard Code of Practice for slating and tiling, BS 5534 : Part 1: 2003 gives the following recommendations for single lapped tiles:

• 38 x 25 mm tile battens for rafter centres up to 450 mm.
• 50 x 25 mm tile battens for rafter centres up to 600 mm.
• For natural and artificial double lapped slates the British Standard recommends the use of 50 x 25 mm slate battens for all rafter centres up to 600 mm. For concrete and clay double lapped plain tiles the British Standard recommends the use of 38 x 25 mm slate battens for all rafter centres up to 600 mm.

A. The ideal solution for a new build or re-roof project is to have insulation between and under the rafters. Ideally it needs a continuous surface for the breathable sarking membrane so that it can be installed in horizontal runs under counter battens with laps sealed. The next best solution is to have insulation between and under the rafters with no continuous surface for the breathable sarking membrane. In this instance the membrane is installed in vertical runs with laps sealed under counter battens.

A. Based on industrial estimates, life expectancy ranges from 5 years to 30 years dependent on the product used. Each manufacturer provides a product guarantee, which should be used as a guide to longevity.

A. Chippings do provide protection for the roof from ultra violet radiation as well as providing a decorative finish. They also can reduce problems caused by extremes of temperature.

A. It is not advisable to subject brush-applied waterproofing to anything more than light traffic associated with maintenance work. Areas used regularly for access should be afforded suitable protection.

A. There are a number of brush-applied, liquid roof coatings available through your local branch, which provide waterproof protection to most conventional roofing surfaces.

A. A VELUX roof window can generally provide up to 40% more light than a dormer, as it is installed at a pitch of 45o. It can also be up to 70% cheaper. A VELUX roof window also provides a good overall outlook while dormers restrict both the upward and side view.

A. The only practical way to prevent condensation is through effective ventilation. By promoting cross currents of air, the entire roof void will be kept well ventilated and will disperse any water vapour before it can condense.

A. Yes - use copper, brass or stainless steel nails or screws.

A. Yes - a lead sheet sealant is specifically designed for pointing joints between lead and brickwork or masonry. It also provides a long-term, flexible joint, which can absorb temperature changes.

A. A domestic eaves gutter when fixed on rafter brackets should be laid to a fall of not greater than 1:350 to allow for settlement. If there is too steep a fall, an excessive gap would be created between the lowest edge of the roof and the top of the gutter.

A. No - but we stock other profiles that are non-asbestos:Profile 3 is used for sheds and garages; Profile 6 is used for agricultural and industrial applications; and Profile 4 or Trafford Tile is used for remedial and refurbishment work. It is also possible to find replacements for deep profile industrial sheets.