Doing retrofit, conflicting advice on roof side flashing

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INYWIFNW

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We’re about to pull the trigger on the deep retrofit of a 1960’s built dormer bungalow. We’re doing it with one of the One-Stop Shops - I know that raises an alarm for some people, but they have been excellent to date and, as part of my own job, I have some industry knowledge and am happy that they are comfortably the best of the One-Stop Shops. That being said, we are now having an issue with them - please see below.

The house has old, white, thick plastic flashing on the side of the roof, which looks very dated. See first picture below.

As part of externally wrapping the house, we would like to get rid of the old flashing and include a sleeker, more contemporary flashing, more for aesthetics than anything else. See second picture below for the kind of thing we want - not exactly that, but similar.

Our One-Stop Shop guy is telling us they can’t do it as it’s a big job involving re-building the side of the roof. They want to just wrap up to the flashing and in behind it, which will (in my opinion), leave a sloppy finish aesthetically. However, any other local retrofit jobs we’ve seen have the much more contemporary flashing we’re looking for. Our roofer (we have a specialist roofer for a couple of flat roofs involved in the job) is also telling us what we’re looking for is perfectly standard. But we can’t get the One-Stop Shop guy to budge, despite pointing these things out to him. He just says that some contractors take short-cuts and just wrap over the flashing, and that approach will fail over time.

Has anyone any experience of this or anything similar? Thanks.

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You've a tiled roof with an existing overhang to the gable. The vertical while plastic element is called the facia. This overhang has a soffit of circa 150mm. The easiest way for the external insulation people to do it is run the external insulation to the underside of the soffit. By adding 100mm external insulation to a soffit that's 150mm deep this is very easy.

For the one stop shop to modify and create a lower profile and thinner facia they'd have to remove the timber rafter that's supporting that existing plastic facia.

That's easier said than done and involves removing the line of tiles which are bedded in concrete the whole way up, remove the end rafter, fit a new slender rafter, relay the tiles and then fit the flashing. My main fear is removing that line of tiles without breaking any will be difficult. Add to that who knows what type of ends of timber battens they'll find that will be rotten and require replacement.

You really need to measure the dept of the soffit. Lets say it's 150mm which is roughly what it looks like. A better solution would be to add 150mm insulation to this elevation. That way the edge of the existing rafter behind the white facia and insulation will be close to flush. Then you can just add and dress a flashing over to create the look you want.

Related comment - I'd be looking to add 150mm insulation everywhere anyway by default. The large cost of externally insulation is the labour. Increasing the thickness from 100mm to 150mm is about 5-7% of the overall cost of the external insulation but you're getting a much much better thermally insulated building.
 
Maybe this thread is also of relevance?

Roof verge - repair/repoint wet verge or opt for new dry verge

Hello, Like lots of people we had some roof damage during the last big storm and had that repaired. However, I was an absolute nervous wreck all that night listening to noise in the attic and swore I would ‘future proof’ the roof to the best of my ability and not go through a night of worry...
www.askaboutmoney.com
 
Thank you very much Duddaa - that is tremendously helpful. I may be back to discuss further when I have discussed your suggestions with my retrofit adviser.

And thanks Clubman - a few useful nuggets in there.
 
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