Residential roofing: solutions for real scenarios

John MercerBy John Mercer, technical manager at Sandtoft

Each week Wienerberger receives technical enquiries through its Roofapedia website, mainly from homeowners, regarding their roofs. In this months’ article, I will share some of these with you, along with the replies we give. For roofing contractors, it is particularly important that you are aware of the kind of concerns your potential customers may have. These are genuine questions and answers.

Question: I live in a semi-detached house. My neighbours recently replaced their roof, leaving a gap between front and back, through which you can see daylight and rain is getting in my loft. They also cracked some of my tiles after removing them without my permission. The roof looks a mess and my tiles are uneven; what can I do?

Answer: Of course, you have every right to expect that your roof is left in a good state of repair and serviceable if any work is done to your neighbour’s roof. There should be a bonding gutter detail to weather the junction between yours and your neighbour’s tiling. You should start by asking your neighbour to have the roofer return to rectify the problems. That is always the best way to resolve any issues. In fact, I would always recommend that homeowners inform their neighbours before starting any work like this as a matter of courtesy and to minimise the risk of problems arising during or after the work is done.

If you cannot get the problems fixed by the roofer then you may need to appoint your own contractor and claim the cost back from your neighbour – but that has to be the absolute last resort.

Question: Is roof insulation foam sprayed directly onto the underside of roof tiles a good thing?

Answer: You will find that many UK roof tile manufacturers and roofing contractors do not recommend the use of sprayed insulation foam. There are a number of potential problems with this:

1) A roof structure must be able to ‘breathe’ – the foam may prevent this and so can contribute to eventual timber rot.

2) Very often foam is applied because the tiles or slates are old and starting to slip. If the roof leaks at all, the foam will hide the source of the leak, with water entering the structure, possibly undetected for a long period. Again, this could eventually lead to timber rot.

3) If the roof is old and there is no underlay, then it is always better to have the roof replaced. This enables modern, breathable underlays to be installed and the insulation can be upgraded at the same time, without any long-term risks to the integrity of the structure.

4) You may well find that the cost of a new roof – i.e. strip and re-tile – is around the same as the cost of the foam, therefore it makes sense to have a new roof.

I suggest that if you have concerns about your roof that you ask some local roofers to quote you for stripping and re-tiling the roof, and compare the cost against the cost of the foam.

If your roof is in good condition and you just want to upgrade the insulation, it is better to use conventional insulation, particularly if the insulation is over the horizontal ceiling.

Question: My roofing felt has failed going over the fascia. It seems easy to repair but should I replace with breathable felt or replace with traditional bituminous felt to match existing?

Answer: Ideally, you should not use either breathable or bitumen felt – neither is very good under long-term exposure to sunlight. Nowadays, the common solution is to use plastic underlay support trays. The underlay laps over the tray without extending into the gutter and the tray supports it so that the underlay does not sag behind the fascia. The trays do the job of extending into the gutter and are very resistant to UV light. Alternatively, use a more robust underlay such as type 5U at the eaves.

Question: I have just had a new roof fitted and I can hear the tiles chattering in high winds. I was advised to get some tile clips, as these would help.  I do not know what they look like or where to get them from. Can you help?

Answer: Tile clips can help reduce tile chatter but they must be fitted with the tiles; in other words, to fit the clips now would require the tiles to be taken off and then re-fitted. If the roof has only just been fitted then you need to ask the roofer to come back to install the clips, as this should have been done in the first place.

Rather than taking the tiles off, another option is to try to identify the area where the tiles are most prone to chatter. Often, it may only be a very small-localised roof area where the tiles are chattering. Ask your roofer to apply a small dab of adhesive under the bottom right-hand corner of the affected tiles – it only needs to be a very small amount; too much adhesive can interfere with the tile interlocks and cause leaks. The adhesive will act as a pad to prevent the tiles lifting in the wind.

Question: I have small clay plain tiles on my roof and I can see daylight through a couple of areas in the loft. Do I need to replace the whole roof or can I just have a few tiles replaced?

Answer: Presumably, if you can see daylight, this is quite an old roof which does not have underlay between the tiles and roof timbers? If there are a few tiles missing or broken, you can just have these replaced. However, the risk is that this can be the first signs of a roof in need of more major renovation.

I recommend that you find a local roofer who can firstly replace the missing or broken tiles, and secondly advise you on the state of the roof generally and whether it does need replacing. There are many advantages to having the roof covering replaced; as well as having new tiles and fixings and extending the life of the roof by many years, it enables a modern, breathable underlay to be fitted and the insulation to be brought up to current Standards.

Send us your queries so we can look at the types of problems roofers are encountering on projects. Email

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