Roof Shop - Frequently Asked Questions

Frequently Asked Questions

Questions: (Click to Expand)

What is the recommended thickness for loft insulation
The current regulations state that a minimum 270mm of loft insulation is required.
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I already have some insulation in the loft but it is not very thick, will this have to be removed or can it be topped up?
Any existing insulation can be left in the loft and an additional layer added to it to bring it up to the required minimum thickness. It does not matter how long the existing insulation has been in the loft it still retains its insulant value.
Is there anything you don't stock?
There's not much we can't get for you. With over 140 branches nationwide we keep most items in stock across the network - alternatively our close links with our suppliers means we can source products very quickly.

If you can't see what you're after just ask; the odds are we can get you what you need.
How should a room-in-the-roof construction be ventilated?
Using the roof space is an excellent way of creating additional space within the original building envelope. However careful attention must be paid to the ventilation and insulation requirements in this type of construction. Unlike in a house where the loft space is not used, in this type of construction the room-in-the-roof temperature is approximately the same as the rooms below. Depending on the precise position of the insulation in relation to the roofing underlay there may or may not be a cold roof void sandwiched in between which needs to be appropriately ventilated.

For constructions where the insulation is either on top of rafters and/or fully filling rafters a vapour permeable underlay can be supported by and placed directly in contact with the insulation so long as the ceiling below is well sealed. If these criteria are met then for most common roof coverings, except less air permeable fibre cement and metal roof coverings, no further ventilation is required.

However for constructions where the insulation is partially filling and/or fixed below rafters or where the insulation is on top of and/or fully filling rafters but the ceiling below cannot be well sealed, then the gap between the underlay and the insulation needs to be ventilated or in the latter case a gap created (with counterbattens) and ventilated. Where a sloped ceiling and insulation deviates from the line of the rafters a gap will be created between the insulation and the underlay, which needs to be, ventilated e.g. a mini-loft above a room-in-the-roof with a horizontal ceiling. In all of these constructions, the method of ventilating the gap depends on whether the ceiling below is well sealed or not. If well sealed then high level ventilation equivalent to 5000mm² per metre run of the gap is sufficient. If the ceiling is not well sealed then both low and high level ventilation of the gap is required equivalent to 25,000mm² per metre run and 5000 mm² per metre run respectively.
How do I select a good quality natural slate?
Selecting natural slate can be a complicated process for the following 5 reasons:

• There’s so much choice.
• You can’t tell how good a slate is just by looking at it.
• The market is not rigorously controlled.
• Different people will tell you different things.
• Good quality and reliable information is hard to find.

As the largest distributor of natural slate in the UK we want to make life as simple as possible for you and for us.
We now offer the following 5 services to make choosing slate simple:

• We have split our range of slates into 5 categories from A+ to D, so you can instantly assess the overall quality.
• We have included the European test results for our range of slates inside this brochure so you can check everything from
the slates’ strength to it’s carbonate content.
• We will source test certificates for you if necessary.
• We have a nationwide team of dedicated slate specialists that will do everything from offering free samples to site visits.
• We commission an independent laboratory to run frequent tests on our slates. If a slate falls below our criteria it is
removed from the range.

These 5 services are unique in the industry and signify our commitment to offering expert, unbiased and reliable advice.
5 Key problems solved by 5 unique services and 5 distinct ranges …slate made simple!
Why is it preferable to dry fix the perimeters of a roof?
The perimeter areas of a roof such as the ridge, verge and hip are the most vulnerable to damage by wind uplift and driving rain. The traditional method of fixing tiles and fittings at these points is wet mortar bedding or wet fixing. The strength and consequently life of mortar is highly dependent on the skills and knowledge of the roofing contractor. Incorrect mixes, poor preparation and careless workmanship can all lead to problems and eventually to costly repairs if the roof is to remain weathertight in the long term.

During the storms of the late 1980s most of the damage to roofs was as a result of failing mortar. However developments in roofing technology have led to the introduction of 'dry fixing' systems. As the name suggests dry fixing does not use mortar but secures the hip, ridge or verge tiles to the structural timber using screws or clips. Dry fix products are also much simpler and quicker to install and their success and long-term durability is not dependent on the skill of the roofing contractor. They can also be fixed in wet weather, which can have a significant effect on the build schedule.

Such is the concern about ways in which roofs are fixed that BS 5534: Part 1: Slating and tiling states that the two end ridge tiles and any other tile that ends a run of ridge tiles, e.g. around a chimney, must be mechanically fixed to protect against wind damage.
What level of ventilation must be provided into the roof void of a normal pitched roof?
The equivalent of a 10mm continuous air gap. This is usually provided by a soffit board with a single row of slots.
Do I need to ventilate if I use a breather membrane?
It really depends upon which membrane you are using, as the quality can vary enormously. Market leaders like Tyvek and Klober manufacture products that claim no additional ventilation of the roof void is required. Always check manufacturer guidelines before deciding whether to ventilate or not.
What is ponding in the eaves?
Ponding in a pitched roof occurs behind the fascia board where the roofing felt may sag and allow water to accumulate. You can use an underlay support tray at the eaves to prevent this happening.
What are the most common ways of providing ventilation to the roof void?
The two most common ways are:
- Over the fascia via an over fascia ventilator unit
- Or through pre-cut slots in the soffit board.
Do you supply reclaimed tiles and slates?
Yes we offer a free reclaimed tile and slate matching service and all our reclaimed stocks are categorised by type, colour and texture. All our materials are individually inspected and graded according to weathering and quality.
The use of reclaimed roof tiles continues to remain popular as more people redevelop or extend existing properties. In certain areas of the country the conversion of barns into dwellings has created demand for quality reclaimed products, particularly handmade clay peg tiles to create the look and feel of a period property. Combine these factors with the current trend of building oak frame "barn style" garages and it illustrates the growing demand for reclaimed roofing materials. Categorised by type, colour and texture, all our materials are individually inspected and graded according to weathering and quality. This ensures that our free identification and matching service can readily select any of the million stock items to blend naturally with a building’s existing architecture and materials. Our range of reclaimed products include machine and
handmade clay plain tiles as well as sort after clay peg tiles. In addition ranges of slate, concrete and interlocking clay tiles are available, many of which are no longer manufactured as new.
I don't have a fascia board on my property how would I fix my gutter?
If you have the rafters showing you can use rafter brackets, we can offer you the option of a top rafter or side rafter bracket depending on how much access you have to rafters. We also have rise and fall brackets. You can also bed a stake into the brick work and use a support bracket which you can alter the height on if you wish to incorporate a fall.

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Frequently Asked Questions