WillH83

Good morning all, @bassanclan unfortunately that idea did not land with the BCO as they are concerned about adding additional hangers to the doubled headers.... I also suggested just adding new doubled joists at one side but the BCO said that they must be fixed to the existing joists hence we are back where we started! and yes it is a flat roof so really shouldn't be this challenging.... @Mr Punter I would have assumed the same but it seems that the BCOs are forever looking for new reasons to exist! Thank you all for your thoughts so far - if anyone could point me to the correct part of TRADA or other approved docs which may shed some light on this it would be greatly appreciated!

Thank you for your input so far @ToughButterCup A good idea thank you - I have added a quick sketch which I hope clarifies the issues! @bassanclan That was plan A but unfortunately every combo / of roof light size seems to end with the same issue... @Redbeard that seems a good solution but no purlins here! I can only assume that this is a fairly common situation when retrofitting into older properties, surely there must be a solution that keeps the BCO happy!?

Good morning all, I was hoping someone may have encountered this same issue… I am installing roof lights into an existing roof structure so I will be keeping the joists and existing deck. For the openings I will double the joists either side and add double headers as per normal. However, due to the spacing of the joists, the doubled joists will still be too wide for the upstand so I will need to add an extra length of timber between the two headers to support one side. I have discussed with BC and they were also unsure how best to proceed as it seems that you should not add additional fixings into headers…. I have exhausted TRADA / BR approved docs etc in search of a solution but have not managed to come up with anything useful. Any advice would be greatly appreciated!

Thank you all for your advice - I have decided to play safe and install two roof lights rather than one large one which leaves at least one joist intact between them. After a little more reading around I have decided that this would be a good time to learn how to install GRP as it seems better suited to the layout than EPDM. Now I just need to wait for summer to start!

Thank you both - I think I shall do exactly that...

@joe90 thank you - I was thinking much the same.... I was hoping to get away with leaving their roof unscathed but it seems I may not!

Hi all, I was wandering if anyone could help me with suggestions as to how to marry up my new warm roof build up with my neighbour’s property? The issue is that my roof was installed about 50 years ago and since then my neighbour’s property has been extended meaning there is no access to the existing fascia etc. to make this even more fun, I am going to add a warm roof build up of 170-175mm (Velutrix, 150mm PIR, 18mm OSB, GRP over existing deck). This brings the new height to around halfway up their fascia board. I have my neighbour’s consent to take my roof to meet their wall and close the 40-100mm gap which currently exists but I would appreciate any thoughts as to how best to do this while allowing the GRP to run high enough… ie. Should this be behind their fascia board? I have added a picture for reference - the gap is below the gutter line although it does not really show very well. Any input would be greatly appreciated! Many thanks in advance…

Thank you all for your input so far - it is reassuring to hear that both options do seem viable! To answer a couple of the questions raised:- The location does not get that much sun and the room has always been quite cold and dark so any thermal gain would be appreciated! The roof lights that I am planning to buy are triple glazed - the 2x1 is approx 100KG so not too ridiculous! There would be no other foot traffic aside from occasional access for maintenance. I was planning to build the upstands using 40mm Celotex between 18mm ply which should avoid any thermal bridging. The manufacturer sells these for around £500 but I think I should be able to make for approx £80. As I am going to be doing all the work myself, I had settled on EPDM as a covering as I have worked with it a couple of times before and it seems fairly idiot proof - GRP does also look fairly straight forward but it would be a first for me so I may stick with what I know! Any further thoughts on the design of the roof structure, in particular the use of trebled joists in the case of the larger roof light would be greatly appreciated. Joist calculators imply that 150x50mm joists at 400mm centres over a 3m span should be fine to accommodate the additional dead load (approx 200kg total) but it becomes less clear once things are rearranged…. Many thanks!

HI all, I have used this forum for years but finally have to pose my own question rather than simply leech off others… I am replacing the existing felt flat roof on my 1970s kitchen extension with a warm roof build up of (existing) 18mm ply deck / Alutrix vapour barrier / 150mm PIR / 18mm ply / EPDM. I would like to add a flat roof light while I am at it which brings me to my question(s)… The roof dimensions (exterior) are 3.8m x 4.2m and the joists are 150 x 50mm at 40cm centres spanning 3m. I have currently narrowed down to two options which are as follows: 1. Install a 1m x 2m rooflight which would mean cutting 4 joists - I was planning to treble the joists at both ends and double the headers on the long sides (sistering joists and using hangers/fixings etc as outlined in building regs). 2. Install 2 x 1m x 1m roof lights which would mean cutting two joists for each - in this case I would only double the joists at either end but still double the headers. This design would leave two whole joists between the two roof lights. Option 1 is both cheaper and easier in that the EPDM could be a challenge with two roof lights to work around and clearly one window is cheaper than two! However, i feel that option 2 is better structurally but I would really appreciate some input as to the proposed design for option 1. One corner will also sit above a window lintel which is unavoidable in either lay out! Any advice would be greatly appreciated! Many thanks in advance, Will