Small flat roof replacement - help!

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strath44
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Small flat roof replacement - help!

Post by strath44 » Sun Jun 24, 2018 4:27 pm

Hi folks, our utility room roof has been crap for the 3 years we have been in the house had hoped to replace it next year.
There was a dip in one corner and a split so I had a poke today to do some repairs however it is totally shot, I think apart from leak that the lack of insulation and ventilation has led to the huge amount of moisture in the roof.
I have worked a fair bit with plastic coated corrugated metal and would like to replace the roof with it. I am not sure if there is a big enough gap to get the flashing on the house wall and a reasonable run off - thoughts?
I see a lot of people use fibreglass now is it any good?
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wine~o
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Re: Small flat roof replacement - help!

Post by wine~o » Mon Jun 25, 2018 1:12 pm

Fibreglass is good EPDM is even better. How come no guttering though?
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wes56
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Re: Small flat roof replacement - help!

Post by wes56 » Mon Jun 25, 2018 3:26 pm

there is a gutter.see the adjustable metal gutter brackets.

strath 44 you need to remove the whole roof to bare joists and re-do to modern insulated warm roof standards.
if youve got painted-over lead flashing on the house wall does it have an angle fillet below the flashing?
you seem to be missing the left hand joist. all joists should be at 400mm centres.
whats happening at the wall corner just past the down pipe?

fixmyroof has some good vids on u-tube.have a look
strath44
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Re: Small flat roof replacement - help!

Post by strath44 » Wed Jun 27, 2018 2:25 pm

apologies for the slow reply here are some better images below, thank you very much for the comments so far.

The detail at the wall on the house is felt bent up and cut into the pebble dash with I assume a timber angle below.

I will detail correctly with fillet / flashing as required.

I am really struggling on this one if I go corrugated which for me is easiest I will create a dead space near the house from increasing the pitch which I'm not sure how to fill - PIR insulation between the studs then upvc cladding I suppose?

The internal gyproc ceiling is attached to the timber original frame and I was hoping to avoid removing this however its looks unlikely going by the first timbers condition.

If I go corrugated and increase the pitch can I insulate between the sloped trusses as I don't think their will be enough roof for the trusses, then osb, then insulation (say 75mm or 10mm), then 34mm box profile sheet metal AND a suitable flashing which I will guess at being at least 75/100mm deep - all to create a reasonable pitch before I hit the gutter!!

Ahh help!

As a PS i am quite happy fitting this and have help, I have asked for a quote and the only roofer who could attend wanted £2500 to replace 1 joist, the osb and either EDPM or felt he said no insulation is needed - I think the lack of insulation has obviously not helped as it was pretty damp on top of the leak!!!!!!!!!!!!!!!!!!!!!!!! I need it watertoight this weekend so have little time to decide and get onto Jewsons etc to get materials!
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Bob225
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Re: Small flat roof replacement - help!

Post by Bob225 » Wed Jun 27, 2018 2:55 pm

thats done, complete new roof time inc all the timber, when the place next to us got sold the flat roof was past its best 10-15 years before, most of it had to be shoved off the roof i will see if i have a pic

that shouldn't be to expensive to sort, while your at it put a bit more fall on the roof
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Ktuludays
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Re: Small flat roof replacement - help!

Post by Ktuludays » Wed Jun 27, 2018 4:22 pm

Materials won't be that pricey if you can do it yourself

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strath44
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Re: Small flat roof replacement - help!

Post by strath44 » Wed Jun 27, 2018 6:43 pm

Bob225 that looks pretty similar construction, I’m still pretty torn as to the best route, 32deg today here dropping now will go out tonight and strip back more to see what’s there, the pain is the internal ceiling is obviously onto the trusses so looks like that will need done as well.

What is a reasonable run off for grp over 3m truss? 40mm?

Also any recommendations for grp suppliers??
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Re: Small flat roof replacement - help!

Post by wes56 » Wed Jun 27, 2018 10:43 pm

ther are no trusses - ther are joists.
totally strip the roof cover, and the fascias and soffit. leave the joists alone.
clean up all the debris and then photo it on here and you will be helped better.

look up on google diagrams of cold and warm flat roofs to see which king youve got in mind. warm roofs are best by far. some authorities only allow warm flat roofs.
strath44
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Re: Small flat roof replacement - help!

Post by strath44 » Thu Jun 28, 2018 9:24 am

thanks, I'm going to strip it tonight and tomorrow night after work.

I took a bit more off the roof last night and it may be possible to save some of the joists which would indeed make life easier, but I have already ordered 11 145mm joists as I can use them else where in the house I also went with 2.4 x 600mm x 18mm tg osb3 as opposed to non tongue and groove - researching it this looks the better option!

The inner skin top wall plate looks fine but the outer ones are shot, I have pre-emptively ordered 22x100mm wall plate as well in-case.

I'm looking into warm v cold roof - the original was neither!

Any recommended grp supply shops would be appreciated as there are a lot out there online supplying the products!
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