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  • FIRST POST
    • happyhero
    • By happyhero 17th May 19, 4:52 PM
    • 1,190Posts
    • 56Thanks
    happyhero
    Are steels required if I fit large lantern into roof
    • #1
    • 17th May 19, 4:52 PM
    Are steels required if I fit large lantern into roof 17th May 19 at 4:52 PM
    Hi I have a flat roof on an extension that is 6.3m wide and 4m deep. The felt is in a bad state and so I want to get it recovered but we would now like to fit a large lantern into the roof of 4m x 2m.


    Will we need steels or will timber still be ok?


    Ive spoken to one guy who is a builder and he said no because there wont be a major difference in weight compared with all the timber joists and ply sheets and felt etc, but I wondered because the span on one side will be 4m for the opening, what do you think?


    I understand that you double up on the timbers around the opening but is that enough?


    The window cleaner will still walk on the roof to get to everything.


    Any help/advice appreciated.
Page 1
    • FreeBear
    • By FreeBear 17th May 19, 5:07 PM
    • 2,498 Posts
    • 3,377 Thanks
    FreeBear
    • #2
    • 17th May 19, 5:07 PM
    • #2
    • 17th May 19, 5:07 PM
    Hi I have a flat roof on an extension that is 6.3m wide and 4m deep. The felt is in a bad state and so I want to get it recovered but we would now like to fit a large lantern into the roof of 4m x 2m.

    Will we need steels or will timber still be ok?
    Originally posted by happyhero

    You really need to talk to a structural engineer rather than a builder. Depending on the height of the lantern, there is going to be a considerable weight in terms of glass. As this is part of a roof replacement, you will need to do calculations on the thermal properties as well as look at additional insulation in the existing roof. Unless you have a roofer that can self certify the work, building control will probably need to be consulted (might even need planning permission too).
    Her courage will change the world.

    Treasure the moments that you have. Savour them for as long as you can for they will never come back again.
    • a.turner
    • By a.turner 17th May 19, 5:42 PM
    • 324 Posts
    • 137 Thanks
    a.turner
    • #3
    • 17th May 19, 5:42 PM
    • #3
    • 17th May 19, 5:42 PM
    Depending of the size of your roof joists you may need a whole new roof.
    • savemoney
    • By savemoney 17th May 19, 6:44 PM
    • 13,029 Posts
    • 11,625 Thanks
    savemoney
    • #4
    • 17th May 19, 6:44 PM
    • #4
    • 17th May 19, 6:44 PM
    I didn't have any in roof we had two 2mx1.5 roof lanterns but we did require one in the opening from kitchen to integral garage. We needed a new roof went from epdm to fibreglass and stronger timbers though. The roof also had ply rather than previously osb3. Ours was only recently finished, the skypods look amazing and let tons of light in. In fact I dont know why people want a conservatory these are far better and usable room in Winter if you have good insulation


    Also great when it rains and all dirt runs off when it rains properly that is



    https://i.postimg.cc/Fz3NFqnm/20190517-194220-1.jpg
    Last edited by savemoney; 17-05-2019 at 6:48 PM.
    • Davesnave
    • By Davesnave 18th May 19, 7:31 AM
    • 28,411 Posts
    • 100,125 Thanks
    Davesnave
    • #5
    • 18th May 19, 7:31 AM
    • #5
    • 18th May 19, 7:31 AM
    . In fact I dont know why people want a conservatory these are far better and usable room in Winter if you have good insulation.
    Originally posted by savemoney
    They look a very good alternative, but don't assume all conservatories are unusable in winter just because they have glass roofs. Mine is more use then than in summer, and the net heat gain to the house makes it doubly worthwhile on reasonably sunny days.
    'I've suffered for my music, now it's your turn.' Neil Innes, introducing 'Protest Song.'
    • theGrinch
    • By theGrinch 18th May 19, 7:55 AM
    • 2,948 Posts
    • 699 Thanks
    theGrinch
    • #6
    • 18th May 19, 7:55 AM
    • #6
    • 18th May 19, 7:55 AM
    You may need a whole new roof and steel frame as a neighbour did
    "enough is a feast"...old Buddist proverb
    • happyhero
    • By happyhero 18th May 19, 8:42 AM
    • 1,190 Posts
    • 56 Thanks
    happyhero
    • #7
    • 18th May 19, 8:42 AM
    • #7
    • 18th May 19, 8:42 AM
    Thanks guys, yes I want a whole new roof anyway, the old one is very old and there wont be much of it left anyway so may aswell renew the lot. I am thinking all new timbers maybe bigger and a warm roof where there is roof.


    I think I'll have to pick the right glass as I dont want it to cook us inside but I've read some stuff about it being cold in winter. I seem to have got conflicting information when it comes to this so it does concern me.


    I'm hoping with the rest of the roof being a warm roof and the latest thermally insulated aluminium lantern it wont be that bad or noticeable in the winter.


    Any of you had experience with one of these in winter?


    I'm not sure what glass I should pick yet that does a good job, any ideas?
    • a.turner
    • By a.turner 18th May 19, 11:46 AM
    • 324 Posts
    • 137 Thanks
    a.turner
    • #8
    • 18th May 19, 11:46 AM
    • #8
    • 18th May 19, 11:46 AM
    Don't get too hung up on a warm roof being any warmer than a cold roof, it's just the way it's constructed.

    Five winters on and I can't say I've experienced it being cold due a roof lantern.
    • ed110220
    • By ed110220 18th May 19, 12:26 PM
    • 1,180 Posts
    • 627 Thanks
    ed110220
    • #9
    • 18th May 19, 12:26 PM
    • #9
    • 18th May 19, 12:26 PM
    I don't think it's safe to assume that just because the lantern weighs less than the roofing materials it is replacing that it's OK to install without strengthening or even a new roof structure as cutting a 4 X 2m hole in the roof may well compromise its structural integrity.

    Warm roof refers to the insulation being above the roof structure so the roof itself is warm while cold roof refers to a more traditional roof in which the insulation is below the roof (eg loft insulation sitting on the ceiling) so the roof structure is cold. Either can offer good insulation and keep the room below warm.
    • DonnySaver
    • By DonnySaver 6th Jun 19, 2:32 PM
    • 476 Posts
    • 187 Thanks
    DonnySaver
    Whilst we're on the subject of roof lanterns, can I ask if the roof has to be totally flat?

    We're considering having a roof lantern placed into our extension but I've always been against flat roofs and I know insurance companies don;t like them either.

    Would the roof have just a small incline on it which is enough for water to run away into a gutter system - thus it no longer being classed as a "flat" roof?
    • EssexExile
    • By EssexExile 6th Jun 19, 3:48 PM
    • 3,715 Posts
    • 2,686 Thanks
    EssexExile
    No roofs are totally flat, or at least they shouldn't be. There must be a slope to encourage the rain to go in the direction of the gutter.
    Tall, dark & handsome. Well two out of three ain't bad.
    • savemoney
    • By savemoney 6th Jun 19, 9:25 PM
    • 13,029 Posts
    • 11,625 Thanks
    savemoney
    Yep my roof isnt 100% flat they put pieces of wood on the beams that are angled from the builders merchant. I have a couple of flat roofs, garage, small extension, porch and bay window none have an issue as long as you get a good roof substrate like epdm or fibre glass
    • Londoner_1
    • By Londoner_1 7th Jun 19, 1:44 PM
    • 143 Posts
    • 43 Thanks
    Londoner_1
    IMHO you would need beams to prevent deflection, the lanterns could wiegh in excess of 100kg. I'm looking to do an extension and put in 2 small beams to for a flat roof lantern weighing 95kg.

    Better to be safe than sorry.
    • ANDY597
    • By ANDY597 7th Jun 19, 3:27 PM
    • 356 Posts
    • 255 Thanks
    ANDY597
    Not sure if this helps, but here is the specs that have been passed by our local planning for my new flat roof dormer. Might give you a rough idea what they will be looking for moving forward but obviously we have different sizes so not exactly comparable

    EPDM roof covering system
    90mm Kingspan Thermaroof TR26 insulation
    Vapour Barrier
    20mm external quality roof deck
    145*145m timber joists
    32.5mm internal insulated plasterboard

    I am curious to hear from the previous poster who went from epdm to fibreglass

    • a.turner
    • By a.turner 7th Jun 19, 3:33 PM
    • 324 Posts
    • 137 Thanks
    a.turner
    Not sure if this helps, but here is the specs that have been passed by our local planning for my new flat roof dormer. Might give you a rough idea what they will be looking for moving forward but obviously we have different sizes so not exactly comparable

    EPDM roof covering system
    90mm Kingspan Thermaroof TR26 insulation
    Vapour Barrier
    20mm external quality roof deck
    145*145m timber joists
    32.5mm internal insulated plasterboard

    I am curious to hear from the previous poster who went from epdm to fibreglass
    Originally posted by ANDY597

    Are you sure they want 20mm roof deck rather than 18mm?
    • ANDY597
    • By ANDY597 10th Jun 19, 3:03 PM
    • 356 Posts
    • 255 Thanks
    ANDY597
    Sorry for the delay in replying, yep 100% just checked the warrantable specs

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