Flat Roof Repair/Replacement

[SlackAlice]

I have a ground floor extension at the rear of my house, which contains a separate bathroom and toilet plus small lobby and External door. It's about 4 x 2mtrs. It has a roof vent/light for the toilet.

The old felt roof needs replacing and I suspect the insulation is either non-existent or minimal. I have two questions.

1) Bearing in mind cost/longevity what is my best option to replace felt with?

2) I shall be getting various quotes from contractors for the job, but what should I be looking for as regards their qualifications?

I shall be 'out' for several hours so if I don't answer anybody for a while please accept my apologies.

Thanks.

[The Builder]

OK Your Slackness ............... the pukka job first. This is what I would do...

Assuming the existing deck is still sound ........ fix 4x2 timber joists on top of what's there. Infill between the rafters with 100mm (4") Celotex of Kingspan insulation. Cover with 18mm shuttering ply. Finish with traditional "built-up" felt.
Built-up felt can be perfectly good if done properly. I use flat-roofers whose jobs have been known to last 25 years.
They use traditional hot pitch, but modern felt is fibreglass based, and a million miles away from the old bitumen felt.
You'll need new (much deeper) fascia boards now. (Not the most attractive thing, but well worth it.)
Use uPVC for the fascia boards ...... white, brown, or black..... or paint them.
Result: new roof covering and fantastic insulation.

If none of this possible, or too expensive, then just let them rip off the old felt. The deck may need replacing as well. Re-felt using the felt I mentioned above.
There are so many bandits who profess to do flat roofing, use only established companies. It possible, get a reccomendation.
Ask at a local Builders Merchants for names.......... or ask a friendly architect.
Virtually anyone can join "Trade Associations" for a fee. Don't necessarily rely on them.

[The Builder]

..... ^^^ "or" Kingspan

[Old_Geezer]

May be just my personal experience but I've not developed much regard for flat rooves over the years. The one at my present place is holding up ok for now, but previous ones I've had seemed to need patching every few years. IMO if it needs major attention, replace it with a decent sloping tiled roof.

[The Builder]

Ahhhh...... OG has hit the spot. Pitched (sloping) roof definitely. It's not always possible though. If you could put up a pic of the existing. I could probably tell you :o)

[SlackAlice]

OK thanks to The Builder & Old Geezer.
I had thought of a rebuild to convert to a pitched roof plus tiles but I don't think the pitch will be enough. There is a bedroom window just above which would only give a height of about a metre. I would also have to consider the rooflight/vent for the toilet. Also might need access for maintenance purposes.

I think I'm basically stuck with a flat roof and had serious concerns about felt and longevity. If modern fibreglass felts have a better longevity, I'll have to reconsider it.
Quite surprised you didn't mention GRP, is there a problem with it?

I'll try to get some pictures up, when I figure out how to ;)

[old-wos-is-name]

my daughter had grp. it was definetly waterproof and will probably withstand most storms and have a long life, but I would think it is far more expensive than felt and board.. I have a lean to with a pitch, covering 4 mtrs with less than a metre pitch height, and thats been great for the last 8 years and will probably last for decades,

[The Builder]

That's what I suspected ......... a window above. A rise of 1 matre over 4 metres will give a pitch of less than 15 degrees. Not enough for slate, but Cambrians (artificial slate) and some concrete tiles will go as low as 15. As long as you're not against the prevailing winds, it would be ok. Even so, by increasing the "head-lap" (don't ask ..... a bit technical lol) that would help even more.

A better way would be to rise as much as you like, then create a "well" (lined with lead) around the window. I wish we could put sketches up on here ;o)

[The Builder]

Right, here's hoping ....... terrible sketch, but I hope you can see the idea.

http://i431.photobuck..._photo/windowwell.jpg

[heathfield]

Horses have hooves, but houses have roofs. Alas, you hear 'rooves' all the time on the BBC.

[SlackAlice]

The Builder

Thanks for your answers. I understood perfectly from your description what you meant and your sketch assisted (quite good actually!).

I think the pitched roof is out. Will seriously consider your idea on the flat roof and started getting local quotes.
EPDM, GRP, Superior Felt, Bitumen. I'm on a steep learning curve here!

John aka SlackAlice.

[Old_Geezer]

I know it is rooves not roofs, my primary teacher spent a long time drumming it into us all that, that was correct, and marking wrong anyone who wrote roofs.

[rov1100]

I would never invest in flat roof felting. Might be OK if you intend to move on in a couple of years. We covered our flat roof twice within a short period and that was the heavy felt.

In the end we used a plastic coated metal roofing which will last a lifetime and doesn't rust. Because its on the roof its not very noticeable from ground level but it does a superior job.

[sandyRoe]

Why does a roof have to have a steep pitch? If one side was just a couple of bricks depth higher wouldn't it carry rainwater away?

[rov1100]

Its surprising what the wind can do to force water uphill!