Roofing FAQ’s

Pitched Roofing –

Roofing FAQ’s – Got a question? We’ve got the answers:

Q: I’m having my house reroofed. What sort of tile or slate would you recommend?
A: If your roof is sound with the existing tiles, the easiest thing is to replace like-for-like. Remember, though, that the roof is often 30% of the visible building. This massively affects its ‘kerb appeal’. If your house is Victorian the roof tiles will be clay or natural slate. However, after the First and Second World Wars many houses were reroofed with early concrete tiles. These do nothing for how the house looks. In these cases reverting to natural slate would transform the appearance of your property.

Q: My house is Victorian but has concrete tiles on the roof, which now need replacing. Are these original?
A: No. Concrete tiles were introduced in the 1920’s and became popular during the post-war building boom. Victorian houses never used these. As natural slate is typically no heavier than concrete tiles, changing back to the original finish would improve your house’s appearance considerably.

Q: My roof needs replacing but the roofer says the rafters look weak. What do you recommend?
A: If in doubt, get a structural survey. This is a common problem with terraced housing where the rafters are only just strong enough. Some roof finishes are particularly light (e.g. fibre cement slates) and can avoid the need for additional purlins.

Q: I want to use a breathable roof underlay. Do I need to ventilate as well?
A: Moisture in the roof space mainly comes from warm moist air leaking into the loft from the rest of the house. You should keep this to a minimum. This is easier to achieve during the build process, but even older houses can be improved with seals on the loft hatches. If moisture continues to be an issue, you can install additional ventilation easily. As every roof is different we would suggest discussing it with your local branch.

Q: If I have eaves ventilation, do I need ridge ventilation?
A: This is recommended. Eaves-to-eaves ventilation only works when there is significant wind. You can install Ridge ventilation quickly and cost-effectively with a ventilated ridge kit. There are several good systems on the market and stocked at SIG branches.

Q: I need to have some slating done and the prices of the slate vary wildly. Why?
A: Natural slate, like any other natural product, varies considerably in physical quality and life expectancy. There is a British standard governing the testing of natural slate, and the results of this are revealing. Some low-cost slates have a life of no more than 30 years, while others can have up to 15% wastage on installation. However a good slate (even an imported Spanish slate) can provide you with over 100 years service, a beautiful finish and nearly no wastage. As you would expect, there is a premium to the material, but good slate costs less in labour. See for more information about choosing natural slate

Q: I have been offered some natural slate for a re-roof, but I can see flecks of gold-coloured pyrites. Is this a problem?
A: Not necessarily. There are many different formations of ‘pyrites’. These are just one of the many different mineral inclusions you find in slates. Visible pyrites can take many forms, some of which are entirely non-reactive. The most risky natural slates can be those with no visible pyrites, but suffering from micropyrites. This is nearly impossible to see even with a trained eye. We recommend customers get a copy of the ‘declaration of conformity’ showing the formal British standard test results. The key result you want is ‘T1’, which means there will be no running rust. A ‘T2’ result means that streaky rust could develop on the roof, but this can be acceptable on hidden roof areas, or on a budget for refurbishment. You should avoid slates rated ‘T3’ as these can rust through and are unsuitable for roofing. All SIG Roofing-supplied slates are T1 or T2. Give us a call and we can talk you though what you need.

Q: I have been instructed to find alternatives to Welsh slate as my budget is tight. Help! A: Welsh slate is a strong, durable and beautiful roof covering. However the cost can be prohibitive in some cases. It is difficult to find colour-matches to Welsh Penrhyn (heather blue) slates, but the Cwt-y-Bugail and Ffestiniog slates are easier to match as they are blue-grey. The Snowdonia National Park Authority has approved a shortlist of alternatives for use in their area, which provides reassurance of the closeness of the match. The list includes SIGA 12, 32, 33 and 172, all of which are available through SIG Roofing.

Q: What warranty is available on the tiles you supply?
A: Some manufacturers offer warranties on concrete or clay roofs, although this is not universal. Average warranties are typically 10-15 years and dependent on the roof being constructed using only their accessories. Warranties on natural slates can also vary, but are typically 30 to 75 years for imported products, and are up to 100 years for Welsh slate. Ask your local SIG Roofing branch for details.

Q: What is a competent roofer?
A: Competent Roofer is a scheme allowing contractors to self-certify their work. If you do not use a certified Competent Roofer for your re-roof or new-build work, you will have to pay for local authority building control to certify the workmanship. This is the law and failure to provide certification can prevent you from selling your house. The cost of LABC visits varies, but it can cost time on the job too. We strongly recommend using Competent Roofer members. Their workmanship is regularly assessed for quality by the NFRC (National Federation of Roofing Contractors), and they are less prone to delays caused by inspections. See our offer page for reduced joining fee.

Registered Office: SIG Trading Limited, Adsetts House, 16 Europa View, Sheffield Business Park, Sheffield, S9 1XH. Registered in England No. 01451007 VAT No. GB 487 01733