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need help converting a flat roof to a pitched roof


 
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beezo

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Location: Cheshire,
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PostPosted: Wed Aug 18, 2010 9:02 pm Reply with quote

Hi guys,

my mum and dad had an extension built around 20 years ago which has a flat roof. The roof is still sound with no leaks but the have decided to put a pitched roof on it for piece of mind so as im quite handy i thought i would have a go at doing it myself even though i have never done this before from scratch.

Problem is, I would like some advice before I start from all you experts please. Im will upload a plan with dimensions and a few pics so you can take a look. If you could then offer me any advice i would be eternally greatful





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freddymercurystwin

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PostPosted: Wed Aug 18, 2010 9:15 pm Reply with quote

What a waste of money, why on earth would you replace a flat roof that wasn't leaking or was in good nick? In anycase, they've had 20 years service at least from their existing flat roof so they clearly have an unfounded negative belief don't you think? Tell them to save their cash and go on a flash holiday instead.
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beezo

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PostPosted: Thu Aug 19, 2010 12:30 pm Reply with quote

freddymercurystwin wrote:
What a waste of money, why on earth would you replace a flat roof that wasn't leaking or was in good nick? In anycase, they've had 20 years service at least from their existing flat roof so they clearly have an unfounded negative belief don't you think? Tell them to save their cash and go on a flash holiday instead.


They have wanted it done for a few years now mate. The reasons behind it is after 20 or so years its stating to get pretty tired so even though its not leaking now, they want to get a pitched roof on it before the problems start. Also mate, they are thinking about when they sell up!! houses with flat roofs dont appeal to buyers and often want a drop in price because of it. Every year my dad gets on the roof, clears it off and put bitumen on dry cracked areas and at 67, he's getting on abit to be doing thAT NOW

So guys, if anyone can offer me some info, it would be much appreciated.

P.S anyone have any idea how much it will cost to do this myself and how much it will cost to get someone to do it for me
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masona

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PostPosted: Thu Aug 19, 2010 12:56 pm Reply with quote

Useless information, have done mine similar size roof with gang nailed trusses with marley roof tiles cost approximately £3500 in 1989, left the flat roof there for loft floor, only cut the flat roof where the wallplate round the edge, will need drawing plan permission. You can get a free quote with the roof trusses company then the roof tiles and materials to give some idea of costs
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beezo

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PostPosted: Thu Aug 19, 2010 4:03 pm Reply with quote

masona wrote:
Useless information, have done mine similar size roof with gang nailed trusses with marley roof tiles cost approximately £3500 in 1989, left the flat roof there for loft floor, only cut the flat roof where the wallplate round the edge, will need drawing plan permission. You can get a free quote with the roof trusses company then the roof tiles and materials to give some idea of costs


im sorry but have i upset some people on this forum??

i have asked for some advice from people that know what they are doing and all i seem to be getting is 'attitude' from members of this forum. The first reply i got to this thread said 'what a waste of money' im sorry but to be fair I didnt ask for his opinion but he felt he had to air it on the thread which was no help what so ever to me. The secound guy said 'useless information'. now im not sure what he is refering to but why not say maybe, we need more info on this, could you tell us that etc instead of just saying 'useless infomation. If you ask me for more details I will find it for you no problem. At the end of the day its you guys giving your knowledge free, which i greatly appreciate so I will go out of my way to get whatever you need.

i thought this forum is all about helping people with DIY jobs and helping people save money, so come on guys, be fair, i just want advice as at the minute I totally stuck
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masona

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PostPosted: Fri Aug 20, 2010 9:21 am Reply with quote

beezo wrote:
masona wrote:
Useless information, have done mine similar size roof with gang nailed trusses with marley roof tiles cost approximately £3500 in 1989, left the flat roof there for loft floor, only cut the flat roof where the wallplate round the edge, will need drawing plan permission. You can get a free quote with the roof trusses company then the roof tiles and materials to give some idea of costs


im sorry but have i upset some people on this forum??

i have asked for some advice from people that know what they are doing and all i seem to be getting is 'attitude' from members of this forum. The first reply i got to this thread said 'what a waste of money' im sorry but to be fair I didnt ask for his opinion but he felt he had to air it on the thread which was no help what so ever to me. The secound guy said 'useless information'. now im not sure what he is refering to but why not say maybe, we need more info on this, could you tell us that etc instead of just saying 'useless infomation. If you ask me for more details I will find it for you no problem. At the end of the day its you guys giving your knowledge free, which i greatly appreciate so I will go out of my way to get whatever you need.

i thought this forum is all about helping people with DIY jobs and helping people save money, so come on guys, be fair, i just want advice as at the minute I totally stuck

Calm down icon_exclaim.gif , apologies if I wrote it wrong, the useless information is referring to the price £3500 in 1989 icon_exclaim.gif We are now in 2010, might be the same price or might be a bit dearer now maybe I should've left this out icon_question.gif I did say you can get a free quote with your drawing for the roof trusses and the drawing to the roofing supplies who will tell you the total price of roofing materials which you wanted to know for doing it yourself and if you can't do it then you all got to do is to add carpenter labour which can be difficult to quote as in difference area tradesman rate etc. Also will need to add drawing plan costs to BCO.

The life of 3 layers of bitumen roofing felt is approximately 15-20yrs if done properly, I've seen some of them 10yrs in poor condition.

The advantage of a tiles pitch roof, the rain noise is quiter, looks nicer, improving rising heat loss, added loft storage space depending if access is available and it's maintenance free

Flat roof is cheaper in the long run also there're other better roofing materials out there now claiming 30-50 yrs warranty, the problem with most flat roof is the chipboards when leaking is like weetabix and should be exterior plywood instead, this will also add more cost if the boards need to be replaced. Most of them don't have cross air vents and soffit vents which is important

It would be cheaper just to renew the roofing felt but if cost is not an issue then go for the pitch roof also a lot cheaper than doing yourself but I don't know what you're capable of doing in carpentry.

Looking at your drawing and done the angle pitch calulating and you're just on the border line of 14-15 degree! to go under the bottom of the window cill, (will need to see the roof on site to confirm) the lowest roof tile pitch and off my head I think it's the marley wessex interlocking tile which have a low 15 degree pitch, however there're are many ways of doing pitch roof to allow for your window.

The reason I've done mine is because I've no plan of selling up and so less maintenance as I get older icon_wink.gif

ps: do a search on flat roof, one of them just lately http://www.diynot.com/forums/viewtopic.php?t=235800
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theoldun

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PostPosted: Fri Aug 20, 2010 3:17 pm Reply with quote

Masona, Not trying to contradict you, this is the pitch that I come up with.

You have half span back of plate to house wall of 2480. Your existing height from roof to underside of sill is 820, add say 200 for existing joists to give top of plate = 1020 rise. Deduct 225 for lead flashing and girth of tile up stand = 795 deduct HAP on rafters 100 = 695. So you have a half span of 2480 and a rise of 695 which gives you a pitch of 11.25 degrees.
Redland Regent through coloured go down to 12.5 degree with a 100 headlap. You could take a chance with these by double felting and reduce to 125 headlap, but there would be no guarantee that roof would be water tight, plus in my opinion a tiled roof on such a shallow pitch looks naff.
There are two ways round this problem.
1. Brick up the bedroom window, fit velux window in main roof above bedroom, and fit fireproof doors to all rooms connected to fire proof escape route to main escape door.
2. Form a flat lead roof below the window and take up the apex of the roof each side of window up to sufficient height above window sill to give a 22.5 degree pitch. In your case to give 22.5 degree pitch your apex would need to be 450 above underside of sill. This will just keep you under 4000. We run lead cheeks up each small half gable.
Your next problem is the wrap round on your hip. You will have an unequal pitch. This can be overcome by adjusting your HAP on the short pitch but leaves you with a different width soffit, however with a bit of jiggling around this can be made to look presentable.
Can you do it? I do not know your capabilities, but will say, even though it is only a small hip, unless you have set out and cut hip jacks, birds mouths and understand angles, then you have not the easiest of jobs going.
If you want to keep your existing ceiling joists and ceiling then your main problem is going to be where you have to cut through existing roof to get new rafters on to plate and to angle of ends of existing joists, you will have to make each hole water tight until new roof is tiled in, plus you can guarantee that where your hip rafter will sit there will be a joist, possibly two that will have to be moved.
If you asked us for a quote, done a few quick figures and we would charge for lead flat below window and 22.5 degree pitch tiled roof £5960.00 plus VAT.
Going to say one more thing young man, I am older than your Dad, so think I have a right to say that I agree with Freddy Mercs advice 100 per cent. Wish I had taken a few more holidays when I was 67. When you get older, your mind would still like a holiday, but your body does not always allow it. One other thing, donít let your Dad go up on the roof, get your self up there.
Regards. oldun
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noseall

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PostPosted: Fri Aug 20, 2010 4:41 pm Reply with quote

theoldun wrote:
So you have a half span of 2480 and a rise of 695 which gives you a pitch of 11.25 degrees.


Actually it is 15.65 degrees Old Codger. icon_razz.gif
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masona

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PostPosted: Fri Aug 20, 2010 4:47 pm Reply with quote

theoldun wrote:
Masona, Not trying to contradict you, this is the pitch that I come up with.

No problem icon_wink.gif you maybe right depending on calculation figures and all depends where the wallplate height will be or use the exisiting wallplate at the lower level, my angle pitch was just a guideline depending where the wallplate will be, you can get away with difference angle by bringing the wallplate inner depending how the fascia and soffit will finish, the only way is a site visit. I do agree, just re-felt it, less worry for the next 15yrs + and enjoy life to full icon_wink.gif I beinging to wonder if I've spent too much money on my property and not enough holiday icon_exclaim.gif
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masona

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PostPosted: Fri Aug 20, 2010 4:48 pm Reply with quote

noseall wrote:
theoldun wrote:
So you have a half span of 2480 and a rise of 695 which gives you a pitch of 11.25 degrees.


Actually it is 15.65 degrees Old Codger. icon_razz.gif

I didn't think I was far off allowing the bottom cill window, however a site visit would confirm it. What a shame Cheshire is too far from me icon_twisted.gif icon_wink.gif
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theoldun

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PostPosted: Fri Aug 20, 2010 7:22 pm Reply with quote

noseall wrote:
theoldun wrote:
So you have a half span of 2480 and a rise of 695 which gives you a pitch of 11.25 degrees.


Actually it is 15.65 degrees Old Codger. icon_razz.gif


Actually, I make it 15.66 degrees Nose, but just to b*gger everything up even further, I humbly apologise that I made a typing error, it should be 3480 and not 2480 and that with a rise of 695 should give 11.29 degrees. Agree that in my post I said 11.25, reaon being that I think 11.25 looks more pretty than 11.29. Truth was I guessed it. icon_biggrin.gif
Hope you had a good holiday and did not investigate any wells. icon_eek.gificon_lol.gif
oldun
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