Constructing a dormer

sintra · 3 Oct 2008

Hello,

I am converting my loft at the moment and i require 2 dormers in it, it will need an apex roof 45 degrees pitch approx, for a 1200 x 1200mm asement window and be leadwork to front and sides.

I am considering a couple of options.

Option 1 - Get a joiner into construct them for me, what kind of costs do you think i would be looking at for this ?

Option 2 - Attempt to construct them myself, but im not sure if i have got enough skills for this, does anybody have any experience of this also what cost would these work out at.

Option 3 - Buy pre-fab GRP dormers and install them myself, has anybody used these before also can anybody recomend any company for these.

Cheers

Darren

^woody^ · 3 Oct 2008

Dormers are easy.

Just make the sides in a timber stud frame, and make the roof as a series of trusses.

You will have the sizes and angles, so just make them in the loft or down on the floor. Assemble to check everything and then dismantle. You may like to do the fascias/soffits at this time, or you can do these afterwards up on the roof

Then, cut your opening and double the rafters each side and fit the trimmers.

Then assemble your pre-made panels and trusses on the roof. Then fit your cover/membrane

sintra · 3 Oct 2008

Thanks for your reply,

you say they are easy, are you sure

Must admit though they do look quite simple in reality. My main concerns are getting it water tight so there wont be any leeks, can you offer any advice on this ?

Cheers

Darren

^woody^ · 3 Oct 2008

If you don't think that you will get it watertight in a day, then you need a tarpaulin or some days when no rain is forecast.

Once you have the frame and roof up, then you fix your felt or membrane. The time consuming bit will be lapping it and adding new sections into the existing roof felt.

The felt on the existing roof should be formed into a 150mm upstand up the dormer cheeks - which will probably mean some new felt sections put in as you will have cut the felt back when you cut the opening out. Then the felt/membrane on the dormer cheeks will lap over this.

You then lay the valley felt for the roof and adapt the laths

Presumably there is some designers drawings to follow, but these may not be detailed so you may like to google for some basic roofing details if you are not sure how it all fits together

noseall · 3 Oct 2008

although i share woodys' optimism for a pop at diy, i think this one is a little beyond dredging out all your old carpentry tools and a book on "how to build dormitory roofs".

get a pro' in.

^woody^ · 4 Oct 2008

Yeah, probably right

sintra · 4 Oct 2008

Dam you guys

Now im confused

I have a friend who did his joinery aprentiship about ten years back but only lasted a couple of years at it, he has said that he will help me do them, he says he hasn't built one before but is pretty confident he can do it. What do you think ???

seasickstevie · 6 Oct 2008

sintra said:
... What do you think ???

It's October. There's an 'R' in the month.

You should be ok.

AndrewSchofield · 20 Oct 2008

I had a builder in to build the 'shell' of a dormer this summer. I would have dearly liked to have a go myself but decided in the end that i didn't have the time to do it myself. If you've got plenty of time then give it a go and if you've got someone with some qualification/experience you should be alright. Having watched them build it (i didn't literally stand there and watch them) it doesn't look that difficult to do but they did it much quicker than i could have done which is a big factor when you've got a big hole in your roof!!!

Try and work out how long it'll take you - and then double it - things always take longer than you imagine and you're bound to encounter some problems along the way!

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Constructing a dormer

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