Frequently
Asked Questions |
Please select one of the following frequently
asked questions and the answer you require will follow.
If you have any further enquiries that have not been satisfied
please contact
us here.
Q1: If I have eaves ventilation do I need ridge ventilation?
A1: 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.
Q2: What are the benefits of using a dry ridge system?
A2: 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
Q3: How do I know if I am using the right batten sizes?
A3:
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.
Q4: What are building Regulations Part L&J?
A4:
Part L of the Building Regulations (England And Wales) concerns the conservation
of fuel and power in buildings. The amendments to Part L came into effect
from April 1 st 2002 and are split into two parts. Part L1 deals with dwellings
and L2 concerns buildings other than dwellings. The regulations cover the
issues of improved insulation and more efficient heating and lighting systems.
In Scotland the regulations are known as Part J and incorporate some differences
to Part L.
In Part L1 for dwellings there are three methods of compliance that can
be adopted to meet the new regulations:
• Elemental Method
• Target U-value Method
• Carbon Index Method
The Elemental Method is the most straightforward and are met by ensuring
that all elements of the building (ie. the roof, walls, floor etc) comply
with the U-values shown in the tables below. The U-value measurement (the
measurement of thermal efficiency) must be less than or equal to the figures
in the tables below.
Windows, doors and rooflights have their combined values averaged out and
their total area should not exceed 25% of the base area of the building.
U-values for Elemental Method for Dwellings Part
L (England & Wales)
| |
Building Element |
U-value required – W/m2K |
Walls
Floor
Pitched roof with insulation between joists
Pitched roof with insulation between or over rafters
Flat roof with insulation over rafters
Windows, doors and rooflights
• in wood or PVC frames (area weighted average)
• in metal frames (area weighted average)
|
0.35
0.25
0.16
0.20
0.25
2.0
2.2
|
|
These figures are dependent on SEDBUK rating of heating system
U-values for Elemental Method for Dwellings Part J (Scotland)
| |
Building Element |
U-value required – W/m2K |
Walls
Floor
Pitched roof with insulation between joists
Pitched roof with insulation between or over rafters
Flat roof with insulation over rafters
Windows, doors and rooflights
• in wood or PVC frames (area weighted average
• in metal frames (area weighted average)
|
0.30
0.25
0.16
0.20
0.25
2.0
2.2
|
|
These figures are dependent on SEDBUK rating of heating system
The details on this website relating to Building Regulation Part L (J for Scotland)
are only an overview, so please contact your local branch if you have any concerns
or queries at all. Our expert staff will be able to assist you one-to-one,
either over the phone, in a meeting, or on-site.
Q5: What is the best way to insulate a new roof or re-roofproject?
A5:
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.
Q6: What is the life expectancy of roofing felt for a flat roof?
A5:
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.
Q7: Do flat felted roofs need to be covered with chippings?
A7:
Chippings do provide protection for the roof from ultra violet radiation as
well as providing a decorative finish.
They can also reduce problems caused
by extremes of temperature.
Q8: Can
liquid roof waterproofing systems be used in areas likely to be walked on?
A8:
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.
Q9: Do you stock a product that I can paint over my existing flat roof to stop it leaking?
A9:
There are a number of brush-applied, liquid roof coatings available through
your local branch , which provide waterproof protection
to most conventional roofing surfaces.
Contact your local
branch for further details.
Q10: What advantages are there from using a VELUX roof window over a dormer window?
A10: A VELUX roof window can generally provide up to 40% more light than a dormer,
as it is installed at a pitch of 45 o.
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.
Q11: I have noticed condensation in my roof space - how can I prevent this?
A11:
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.
Contact your local
branch who will be able to advise you of the most suitable product.
Q12: Do I need special nails or screws when fixing lead?
A12: Yes - use copper, brass or stainless steel nails or screws.
Q13: Should I use a special sealant for lead?
A13:
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.
Q14: What gradient do I need to lay guttering?
A14: 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.
Q15: Is it possible to still purchase Asbestos Sheeting?
A15: 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.
