Any architect types in the house?

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  • Any architect types in the house?
  • Premier Icon just5minutes

    Looking for a bit of advice here but despite quite a bit of googling haven’t managed to find anything that helps.

    As part of a house refurbishment a glass roof was fitted – not the sort of massive affair you’d see on Grand Designs but a smaller unit about 3m x 1.8m.

    Since installation, water has pooled in the unit whenever it rains – which being glass has a slight concave in it. Although the unit is “self cleaning” the water basically sits there, eventually dries out and leaves the whole unit covered with dirty water marks.

    I’ve raised this a number of times with the architect who specified the roof and the fall on it but he’s basically refused to discuss it.

    What I have managed to establish is that most glass suppliers recommend a minimum fall of 5% with most suggesting 10%. The architect specified 1 in 80 fall, or 1.25% which would seem to me to be the root cause of the glass not draining.

    So for architect types:

    1. Is there a reference guide / common standard on falls that the architect should have taken into account?
    2. Is 1.25% normal, and if not, what is?
    3. How do I resolve the issue when the architect won’t discuss it or respond to written communication on it?

    The finished job has left us really underwhelmed with a permanently filthy rooflight – but as removing it and reconstructing it would probably be a good £5K+ I’d like to try and find a way of getting the architect to help find a solution for us if a cock up has been made.


    Right, 1.25% is far too shallow a fall. 5% is a sensible minimum to prevent pooling. Sometimes you can get away with 3% if you thicken up the glass to prevent it sagging under its own weight.

    The pooling is exacerbated by the deflection of the glass due to self weight (which then gets worse with water sat in in),

    Self cleaning (Bio Clean, Activ etc) glass needs sunlight to activate the coating and start breaking the dirt down. It then needs hosing off not just rain water. This needs to be done even in vertical applications, so would have to be done even more so on a roof, especially with such a low pitch.

    Is the architect a member of RIBA? Maybe worth contacting them to see if they can help or have a some leverage?

    Premier Icon pedropete

    1 in 80 is the normal fall for a flat roof – not sure about the requirements for a glass one. You might want to speak to this lot: Glass & Glazing Federation, for advice. Not sure what remedy you will have against the “architect”. As previous post queried, is he/she RIBA?


    Also what kind of contract did you have with the architect? Any mention of fit for purpose (in which case you have him banged to rights), or reasonable skill and care (in which case you have to prove that he has not done what a competent peer (i.e. another architect) would have done in the same situation). In either case you could probably quite easily prove that they have been negligent in their design, as you would expect a competent architect to either know about the 5% fall, or ask a glass supplier.

    You’ve managed to find out about the 5% fall and you aren’t being paid to design and roof light!


    Is the guy actually an Architect.? You can check on the ARB web site. He will (or should) have professional indemnity insurance which will cover him for “mistakes” like this.
    You need to write to him (recorded) stating your case and giving him a timescale to respond by.

    Premier Icon just5minutes

    Thanks everyone. The person who did the plans is not qualified as an architect but the service / contract is with a RIBA registered firm – I think the root cause is that the qualified person didn’t do the plans or check them. It only became during the build how little input (none) the architect had had in anything leading up to that point – it’s only a small firm so despite checking references and speaking to previous clients this issue was not anticipated.

    Another question for architect types – if this is a screw up, what’s the fairest way of resolving it?


    5 degree – not for self cleaning glass though. I have a Sunsquare roof light and I very much need to get up there and clean it at 5 degrees.


    15.4.2 Slope
    To avoid ponding on the glazing, the slope should be not less than 5° to the horizontal.
    For shallow slopes, exposed situations or long down-slopes, special considerations might be required to
    prevent ingress of water.
    The glazing system should be designed to discourage the accumulation of standing water on transverse
    frame members. This is particularly important with shallow glazing slopes.


    Write to them explaining that you’d like to come to an agreement on a remedy that stops water puddling on your rooflight.
    You could wind up the screws by suggesting that they inform their PI Insurer as they’ve chosen to not discuss this issue with you.
    You could raise a complaint about them to the ARB, although they will only look at complaints about an architect’s conduct or competence.
    Be a bit more forward in expressing your unhappiness, most architects, like most people are reasonable – mistakes do happen, and that is why we carry PI insurance, I’m sure that you’ll find a way to resolve the situation to everyone’s satisfaction.


    Dealing with resolving the issue, clearly the weight of the glass is creating a sagging effect as described earlier. The obvious route to take would be to install a stainless steel ‘beam’ across the centre to support the glass and prevent the sagging. I know it’s not ideal as it interferes with the clean ( or not!) glazed area, but it’s a cheap solution.

    The glazing supplier we’re using for our build advised not bothering with ‘self cleaning’ glass on any of our rooflight sections – said they need a fairly significant fall for the self cleaning to be effective.

    Has anyone else got experience of these coatings? Are they worth the extra?


    Speak to the architect specifically about the issue and put it in writing. If the glazing system specified is not suitable for the pitch then the architect is most likely liable (as the bowing if the glass will inevitably lead to failure of the gaskets). They have pi insurance for the inevitable cock ups. That said you can do 1.5 degrees in glass, it depends on the system. Check what the architect specified for this as it could be correct and the pooling is an aesthetic issue. In which case it’s tricky as although you maybe weren’t made aware it is technically no issue.

    Premier Icon nickjb

    That said you can do 1.5 degrees in glass

    His is only 0.7 degrees, though. That’t a crazy small angle. I put mine it at 8 degrees. Not self cleaning but they haven’t needed a wash yet.

    Premier Icon just5minutes

    this is going from bad to worse…. it’s like Grand Designs but without Kevin or the TV cameras

    So further to my original question we’ve now got a problem of mice nibbling at polypipe heating pipes that have been installed underneath a a sealed (solid oak) and tiled floor. We can hear them crunching away under the floor but due to the lack of any access points can’t do anything to get to them – the air bricks already have mesh over them.

    At the time the build took place I tried to insist on the ground floor heating pipes being installed in the walls just in case there was ever a leak i.e. it’s easier to fix a leak in wall void than wrecking thousands of pounds worth of flooring by tearing it up. I basically got overruled by the architect who refused to instruct the builders / plumbers to follow my request despite having previously agreed to it and previously committed to making sure they followed it – he basically forgot and by the time I came home and said “but the pipework is all in the wrong place” it was too late and I got told that even if I insisted it be re-done they would refuse to do it and he would refuse to make them do it.

    Is there anything in Building Regs that says heating / water pipes must be installed in somewhere that’s potentially accessible in the event of a leak and how to / how not to install pipework under what will ultimately be a solid floor?

    Premier Icon bedmaker

    We can hear them crunching away under the floor but due to the lack of any access points can’t do anything to get to them

    Stuff like that is just mental. I was lucky to get a great architect for my house, recently started out by himself.

    In the course of my work though, I’m often shocked at the daft stuff I see on plans. A layman shouldnt’t really be able to easily pick holes in the work of someone who has studied years to get where they are.

    It seems like there are too many frustrated artists in the business of house design.


    The only question I would be asking someone in your situation (assuming he still isnt speaking to you) is ‘who is the provider of your PI insurance’ and also saying ‘I insist that you put your PI insurer notice of a potential claim on them from me’.
    Then I would go and speak to a professional negligence/construction claims lawyer.
    And check your contract with the architect.


    Regulation 7 – BS 8000 Part 15 – (clause 3.7) provides guidance and recommendations.

    Pipe manufacturer’s also provide guidance on plastic pipe particularly in a situation where it might be susceptible to rodents.

    I hate the stuff myself and even in my own property had the boiler return pipe burst resulting in hot water all over kitchen and a new ceiling in a 7 year old house.

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