Roof Tiles under Window

[boycey9]

Hi,

Building a rear extension and have hit a problem with the roof.
The design is a flat roof of about a foot (To the back of the bay window) then pitched down to the wall.

Where the pitched roof comes under the bay window there is only just enough room to fit the tiles not leaving any room for flashing, any ideas on waterproofing this joint please.

 

[noseall]

Not sure what you mean.

But, the lead flashing should have priority over other factors.

It is not uncommon to say, fix a lead flashing under a window sill prior to fitting either the window or any roof timbers etc, that might interfere later on. The lead is then folded up out of the way then dressed down once the roof tiles are in place.

You would not keep building up to an awkward junction and then say, "oh, what about the lead".

 

[boycey9]

You would not keep building up to an awkward junction and then say, "oh, what about the lead".

Unfortunately when you have no idea on these bits after I have, I have followed the Drawings which show the roof finishing directly under the window sill. The Tiles are not yet fitted and I have a gap of about 55mm between the joist and the underside of the Bay window.
I understand this is not how it should have been but was asking if there is a way around this without dropping the roof as the roof rafters fit in to the Steel that holds up the Bay and this would also need to be dropped which is going to cost me a lot to rectify.[/quote]

 

[freddiemercurystwin]

Really it needs a 150H upstand. It may be OK with a much shallower flashing it may not. In anycase I suspect Building Control may spot it (they should) and expect it to be rectified. Raising the cill or lowering the roof would appear to be your two options. Its not overly clear exactly what's going on here tbh, posting a photo will answer this. It is sometimes appropriate to have a small flat roof where a pitched roof hits the cills on a wall, this may or may not be a suitable solution here.

On a side note, if you have followed the drawings to the letter and they show no 150H upstand for the flashing I would get your 'designer' or whoever you had do the drawings out and ask him what he proposes. That said, when building yourself you do need to think ahead. You have realised this a problem now but surely as soon as rafter or steel was in an alarm bell should have rung.

Anyway post a photo.

 

[boycey9]

Here is an extract from the Drawing, does this make it clearer as this is what i have worked to. Got a tarpaulin on the roof at present and its raining so will take picture later if needed.
The Roof Rafters are notched in to the steel

Thanks.

[/img]

 

[freddiemercurystwin]

Holy Cow!!!

Is this being done under a Notice or were the plans approved beforehand? Your designer needs shooting but as mentioned really this was very predictable.

Anyway there's not a magic workaround as far as I'm aware so lower the beam or raise the cill or take your chances if BC pass it.

Probably easier to raise the cill though not necessarily cheaper. If lowering the roof (pitch) is even an option. It already looks very low, what pitch is it out of interest?

 

[boycey9]

Ive measured the actual angle this morning and it is 15 degrees which is the minimum pitch the tiles are allowed at so not going to be easy to lower it, The window above is uPVC so manipulation will be hard and has a flat roof above it, The BC attended after the steels were installed and ok'd to go to insulation stage, maybe he didnt see this problem occurring either.
Its being done as alawful development and all plans signed off accordingly.
In my defence my head is spinning with all to work out, done a lot of DIY and a bit of site work years ago and thought I would manage better, once the roof is on I will be back in my comfort zone.

 

[freddiemercurystwin]

Lawful Development refers to planning under Permitted Development not Building Regs. Think replacement not manipulation.

15° is too shallow for many roof tiles so that's another big hole you may be about to enter! Building Control often won't approve a roof finish that is not designed for the pitch. Same applies to the rooflights though 15° is the minimum without an additional upstand I recall for most.

 

[boycey9]

The roof Tiles specified are Sandtoft 2020 which I have been assured are capable of handling this pitch with a 100mm overlap, I have sent the plans off to Sandtoft and just awaiting their response to how many tiles etc needed to complete the job.
Ive added another 3D picture that seems to show the flat part of the roof butted up against the underside of the Cill incase this makes a difference.
I Plan to talk to the architect later today but I like to understand all angles first myself so I feel prepared otherwise I think they can try and blind you with science so to speak.

 

[Peter1919]

I suspect you may wel have to lose some of the lower part of your window to allow a proper joint between wall and new roof. Which will not be cheap and may well compromise the look of the whole thing.

It seems like poor design work to me.

 

[freddiemercurystwin]

Aye, agree with Pete, poor design nothing else. You are right about Sandcroft 20/20s they are good for that pitch so that is something. So raising the cills seems the only viable alternative other than chancing your luck with BC or the weather.

Your architect should be shot! Proper schoolboy error that one but an experience builder would have spotted it before he even got out the ground. It would look better with an upstand anyway.

 

[boycey9]

Thanks for the advise guys, This I suppose is the downfall of trying to save money and doing myself, however even with this error corrected I will still be quids in on the quotes I got for a builders finish.

Should the Architect be responsible for such errors?, Is it worth hassling them on it or just bite the bullet and fix it.

 

[freddiemercurystwin]

For a quiet life you could just get on with it. That said IMO they've cocked up big time if they are Building Regs drawings. I would be discussing it with them in the first instance to see what they say. Did they know you were a self builder?

Just to be clear, were any drawings submitted to Building Control for them to approve prior to the works commencing?

 

[boycey9]

The planning stage was all done for me by the Architect, The Certificate I got from the council specifies the drawing names on it so from this I would assume yes the drawings were submitted.
I have spoken to the Architect and he advised he has seen this issue before and that the roofer has always managed to work round it tucking lead up under the Cill and/or using silicone.

I have a very experienced roofer (Friend of a Friend) hopefully coming to have a look for me later and hopefully actually seeing in the flesh (Problem with internet is responses are only as good as the information I give you and as we have already seen my knowledge is not great) may be able to help.

Appreciate all your advise as was sitting here stressing.

 

[freddiemercurystwin]

The planning stage was all done for me by the Architect, The Certificate I got from the council specifies the drawing names on it so from this I would assume yes the drawings were submitted.
I have spoken to the Architect and he advised he has seen this issue before and that the roofer has always managed to work round it tucking lead up under the Cill and/or using silicone.

So do you have a Certificate of Lawful Development? If so this is for planning not Building Regulations. Or do you have a document from the council saying Building Regulations Plans Approval? They are entirely separate parts of the process.

Tucking the lead under the cill or using silicone is bodging it. If your roofer friend is good he will agree, as mentioned tucking it in or using silicone may well work but it ain't a proper job. You could always post your drawing and image in a new thread in the roofing section of the forum as you will get the roofers' responses too.