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Flat roofs ... Horrid things.

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Flat roofs ... Horrid things.

Postby Jimmy Mack » 15 May 2017, 20:27

Part of our house has a flat roof, it was once pitched but for some reason it was converted to a flat one...probably a cheap reason!

We moved in just over 2 years ago and it probably reached it's use by date 15 years ago. It has since been limping along by the looks of things.

Ideally we'd like to convert the back end of the house with an open to roof kitchen and diner, however it's a BIG project and we just can't afford it at the moment.

So back to the rubbish roof... Guess what?...It leaks... But only in one corner, an area of about 1 - 2 sq/m. (I've pulled back the ceiling to check this and inspect for possible tracking)....it's an unusual mezzanine/ attic level over the kitchen.

Is it feasible to try and attempt a patch repair? Has anyone tried this or should I get a guy in with his blowtorch ? I've tried the thick paint and roof silicone but it failed after a season. We're looking for a solution that will buy us a few years so we can save up and do it properly....with a double pitched roof.

Cheers,

Jim

Corner closest in the pic is the problem zone.

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Re: Flat roofs ... Horrid things.

Postby Mike G » 15 May 2017, 20:29

Haul it all off, get some EPDM, do it yourself and never have to worry about the roof ever again...........and all cheaper than repairing torch-on felt.
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Re: Flat roofs ... Horrid things.

Postby Jimmy Mack » 15 May 2017, 20:32

You can see the layout here, it goes house then perpendicular extensions consisting of...metal roof (odd in itself, perhaps a light weight solution), flat roof, garage...garden... workshopImage

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Re: Flat roofs ... Horrid things.

Postby Jimmy Mack » 15 May 2017, 20:50

Mike G wrote:Haul it all off, get some EPDM, do it yourself and never have to worry about the roof ever again...........and all cheaper than repairing torch-on felt.

Cricky... I shall Google this witch craft.

Cheers, Jim

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Re: Flat roofs ... Horrid things.

Postby StevieB » 15 May 2017, 21:39

+1 for EPDM - diy-epdm.co.uk I have used before (no affiliation) but it is heavy stuff over a large area so not a 1 man job I wouldn't think.

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Re: Flat roofs ... Horrid things.

Postby Rod » 16 May 2017, 00:13

I did my shed roof with EPDM - very easy to lay once you've got it on the roof area.

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Re: Flat roofs ... Horrid things.

Postby Jimmy Mack » 16 May 2017, 09:13

Thanks for the feedback chaps :D

After some Googling and YouTube - I can see this does actually looks very do-able.

It's a fair size roof, approximately 5 x 8m PLUS turns, wastage, etc. (200mm seems to be the general advice for this). Recommendations are to lay a single sheet (no joins). An achievable lift & fit for two, up about 4m?

Concerns :eusa-think:

From the inside the sheathing looks to be chipboard, perhaps 18mm. I suspect some will need replacing, hopefully just the area where the leak has developed - is this optimistic? It will be difficult to ascertain exactly what sheathing to order and how much, until I've got stuck in.

The reality might be that the sheathing surface is 'manky' and the adhesive might fail, of does the adhesive stick like 'poop to a blanket'? (Appears to be a rollered water-bourne for the main area and a solvent base for the turns/ edges). The surface might even tearaway with the old bitumen? Is it easy to rip off the old bitumen?


These unknowns make me a little nervous about ripping the top layer... knowing my luck a forecasted heatwave will rapidly becomes a freakish Summer flash flood, especially if I'm on it for a few days replacing sheathing, when the initial plan was a one day peel 'n' lay.

Any experience appreciated,

Jim
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Re: Flat roofs ... Horrid things.

Postby 9fingers » 16 May 2017, 10:10

Older flat roof felt was usually 3 layers, the first tacked onto the decking with roofing clouts and layers 2 and three put on with melted bitumen. I think the newer torch on stuff is only two layers and might be more interesting to remove. An exploratory dig in the damaged area should help see what you have got.
Best to replace with decking ply - lower to medium price as ply goes.

EPDM is usually delivered on a roll and so easy enough to get onto a roof as a roll. Obviously choose a potentially dry day and if you can unroll the epdm and let it relax for an hour or so. then manoeuvre into position, fold back just over half and apply water based contact adhesive supplied for the job to half the roof and half the rubber. Sacrificial roller is useful. once it has got tacky, roll the rubber onto the roof with a hard roller and or soft broom. repeat with the other half using a new sacrificial roller. Once that has all been sorted, nice a smooth etc then do the edges with the solvent based adhesive using custom fittings if needed
There are several good videos on youtube showing the technique.

hth

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Re: Flat roofs ... Horrid things.

Postby Rod » 16 May 2017, 10:17

I think the manufacturers prefer it being laid on a clean fresh surface.
A few years back I had my double garage flat roof done professionally.
I cannot remember if they removed all the old felt but they put a new layer of Stirling board on top.

Yes water-based adhesive for the flat bits and contact for the vertical bits.
Plenty of how-to videos on the web.
For my shed, I laid mine out in situ for 24hrs to "rest and recover" peeled half back then working from the middle, glue then roll out in stages.
Then repeat for the other half - my shed is 4m x 3.6m and apart from help getting it onto the roof, I managed on my own ok.

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Re: Flat roofs ... Horrid things.

Postby Jimmy Mack » 16 May 2017, 14:31

Thanks chaps. Tidy job that, Rod :)

I think the sensible route will be require replacing the deck, it looks as though OSB can be used.

I've done some rough figures based on a roof 8 x 5.5m

    EPDM £464
    Trim, adhesive £335
    18mm OSB £212
    Skip £100
    Fixings & misc. £50

TOTAL £ 1,161

How does that sound?

Considering we likely to be bashing it in the next 5 years ... :eusa-think:


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Re: Flat roofs ... Horrid things.

Postby 9fingers » 16 May 2017, 16:11

Maybe compare with felt which will certainly last 5 years plus procrastination delay on ripping it off.

You should be able to get a rough per sq m price for torch on felt assuming you have cleaned off the old stuff and patched the decking and then do the trade off.

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Re: Flat roofs ... Horrid things.

Postby HappyHacker » 16 May 2017, 23:56

I am +1 for EDPM, I had three flat roofs done with it a few years ago and there have been no problems since.

If you are replacing the decking consider putting some insulation in, I wish I had done so now.
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Re: Flat roofs ... Horrid things.

Postby Mike G » 18 May 2017, 07:02

If you've got an existing ply deck, then over-sheeting with 18mm OSB might be overkill, and it's damn heavy stuff. If the original deck is laid to any sort of fall, and isn't rotten, you may find that 10mm OSB is enough. The other approach, as has been said, is to lay down some sheets of Celotex, and overboard that with 6mm ply, which gets pinned through the insulation into the joists below.

I don't know if you are going to need scaffolding, but at the very least you are going to need edge protection.....a handrail and so on, so that you don't splat onto the tarmac below. That tends to spoil your day somewhat.
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Re: Flat roofs ... Horrid things.

Postby Jimmy Mack » 19 May 2017, 11:33

Chaps many thanks for the responses. (Mike you might want to click your 'back button'... :eusa-whistle:

Yesterday, During a brief break in the days of rain, post water dripping on the boiler, various electrical junctions, wrecking the kitchen ceiling, and ...erm...upsetting the cat ...

:oops:

...I dived on a £60 bodge repair :?

Roofing compound and scrim reinforcement to the top and some 11mm OSB pushed & screwed (into joists /rafters?) up to the split & soggy chipboard underside (inside). The condition of the sheathing here suggests that at some point it'll ALL have to come off (FUBAR).

Feel free to flame me!... It was a miserable experience :cry: ...the scrim was tricky to apply and the (snake oil) compound was like painting with toffee! It has bought us a little time as it's raining now and the tide is held, but for how long?... who knows!...It's all pretty rubbish but will have to do - until we can decide on the extension (£££'s) or a Rubber roof. Though Mrs Jim wants to loose the flat roof entirely.

I now have a pond on the roof (where it sags), maybe I'll get some fish... the cat will like that.

Thanks again,

Jim
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