Are steels required if I fit large lantern into roof

happyhero

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.

FreeBear

happyhero wrote: »

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?

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).

a.turner

Depending of the size of your roof joists you may need a whole new roof.

savemoney

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

Davesnave

savemoney wrote: »

. In fact I dont know why people want a conservatory these are far better and usable room in Winter if you have good insulation.

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.

theGrinch

You may need a whole new roof and steel frame as a neighbour did

happyhero

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

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

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

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

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.