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Tiled pitched roof with velux or flat roof with pyramid lantern

Our existing extension is 4.2m by 4.8m. The current roof is polycarbonate hipped roof. It goes up to 50c in summer (being south facing) and freezing in winter. We plan to replace the existing roof with glass option but was told that it's not the most efficient way. So we are now considering tiled roof with velux or flat roof with lantern. Our house is long and quite dark so the extension roof provides the essential light for the whole downstairs. Therefore we are leaning towards the latter ie lantern. A few questions here hoping someone can help please:
- Which one would be the most cost effective?
- We found a lantern supplier who does installation as well. Who would be able to build the flat roof part? Would it be a roofer or is it more a specialist job?
- As we want to maximise the light, the lantern size we are looking at is 3.6m by 3.6m. Therefore one side of hr internal length of the flat roof would be 30cm - is this large enough?

Any other advise is welcome.
Many thanks!

3 Answers from MyBuilder Extension Builders

Best Answer

There are various angles as to how to advise & discuss your project, but 1st you must decide the priority of cost v light?
The 2 previous answers while both give sound advice, with respect, they also offer certain elements which are a little off the mark.
So, cost, yes the tiled roof & Velux, maybe even a light dome would be more economical and could be constructed quite easily by an efficient roofer with the assisistance of a decent chippy. Some roofers don't do carpentry, just slate & tiling.
The other is a more complex affair.
The flat roof with lantern, known as an Orangery, is the better performing, but costlier option, but also requires more trades.
Most conservatory companies now are quite capable of creating these structures, or converting conservatories into Orangeries by converting the roof, like what you're considering.
Although please take care, as some (mainly the big boys or big discount merchants!) are not what they say and just use cheap unskilled labour, beware!
There isn't an essential need to use rsj's, as cheaper glulams (adequatelly sized) are just as good. While yes, fibre glass is the preferred option v EPDM single ply membrane (no joints). But EPDM is still very good if well fitted.
Good design consideration, symmetry and balancing is very important.
However, both options have greater inherent problems, namely local authority compliance.
As you're using the existing footprint without addition to or out with parameters, there's no requirement for planning permission, it's the Building Regs!
I suspect the original structure wasn't built under any governance, the new consideration under the proposed options/methods, would need these regs. So there lies a greater issue.
The groundwork will not be up to requirements, the insulation levels will not comply, the framework of supporting doors and windows may be to lightweight for the increased weight, volume of translucent material too low etc., etc..
I wood have the compliance element checked out first, or all your efforts on the other issues may be a waste of time, more so money.
A true professional company / individual should be able to do all of this for you (as we could!!), from compliance & advice to design & build.


Answered 16th Jan 2016

The most cost effective would be a a tiled roof with a velux window, But you would benefit from the lantern with natural light.
Either a roofer or a good all round builder would be able to build the flat roof.
I would recommend the lantern to be made to the size of 3.6m x 1.8m not only for the look but also for the additional weight on the roof. If you decide that you want a bigger lantern then a RSJ steel beam would be advised to be fitted to house the extra weight.


Answered 6th Jan 2015

If you are doing a flat roof with a lantern then I would opt for a warm roof since I assume the lantern will meet the current regulations for thermal efficiency.

Opt for fibreglass and use a fibreglass roofer - not a general builder or roofer. Thus way you will get the better end finish by someone dealing with this type of work on a regular basis.

I assume the structural calculations have been sorted, so if you have the plans a good chippy can fit a roof.


Andrew @ Fibretechs - Glos


Answered 30th Jan 2015

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