flue / flat roof problem

[nick60]

morning all, I'd welcome advice on this little problem......

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• nick60
• 2 Aug 2010
• 1

I'm constructing a new flat roof that abuts my neighbours property - all above board, planning permission, building regs etc etc. Problem is that my neighbours flue is very close to the new roof surface, see pic above. We knew it would be close before we started the job, but since the building inspector wanted upstand ventilation the whole deck is now sitting on battens which has made the problem worse.

My neighbour is happy for me do to whatever I need to do as long as it's gas checked etc. What I'm thinking of doing is adding an elbow + vertical straight section to his flue, then encapsulate the elbow/ base of flue in sand/cement using a bit of shuttering to create a box. I'd put a slope on the top of the box and then flash with lead. I might make a lead cap that completely covers the top of the sand/cement box. What do you think? Any better ideas gratefully received! If I do what I'm planning to do should I do the sand/cement before the roof is finished? (what you see in the picture is just the first layer of felt, roofer is back to finish the job in a week or so)

TIA
Nick

 

[masona]

Might be an idea to post this on plumbing for Gas Safe for their advice, from what I understand the flue have a clearance flue regulations but I may be wrong.

 

[mysteryman]

You are heading for real trouble here.

Get advice from a professional - before you are in trouble.

 

[nick60]

mysteryman, I know I need advice, that's why I'm asking on here before doing anything! My building inspector has seen it and he didn't seem too alarmed so I'm sure there's a solution.

 

[picasso]

you need to find out the boiler make and model and post back.

 

[SortedPlumbing]

Looks like your neighbour is gona have to move their boiler, is is there flue overhangin onto your land?

 

[kevplumb]

My building inspector has seen it and he didn't seem too alarmed so I'm sure there's a solution.

probably cos he don't know the regs

 

[nick60]

thanks for posting folks. boiler is an Ideal Standard. I will get the exact model from my neighbour as soon as I can.

Yes, I suppose technically their flue is overhanging my land, but mine does exactly the same on the opposite side of the house! There'a a row of 7 or 8 houses with similar arrangements.

Rest assured my Gas Safe plumber will be on the case in due course - I'm just trying to get some other views while he's on holiday. I thought my idea was reasonable to be honest!

 

[mysteryman]

Any work on this must be done by a professional gas man - which is why I advised you to contact one. This mustn't be done by anyone else. There are all sorts of potential problems, but you also need to know the make and model of the boiler, as suggested above.

 

[Agile]

It all depends on who owns what!

If you own up to his wall then he has no right to discharge over your land and may have to move their boiler.

Next all flue work should be done by a Gas Registered engineer.

Its an old non condensing boiler. So the flue parts may no longer be available.

The minimum which MIGHT be considered possible IF the permitted flue length is not exceeded is an elbow to take it upwards and then another to take it horizontally to a terminal like the existing one. Then all the flue parts are enclosed in a weather tight boxing with a removable panel for access/inspection.

You really should have considered this earlier. To discharge like that over a flat roof needs 300 mm minimum clearance below the bottom of that terminal.

I do hope you are not going to do a dangerous and illegal bodge!

Tony

 

[nick60]

Tony, certainly not! The BCO is all over me on this build so only a pukka solution will do. You're right, we should have considered it earlier, but it got overlooked (by a variety of people I should add, not just me).

 

[nick60]

Mysteryman - thanks. This was never going to be a DIY job. Was just trying to gauge the size of the problem before the professionals take a look.

The boiler in question is right behind this outlet - presumably one elbow + a straight section through the wall. Is it therefore quite likely that this flue can be extended with some extra components? I assume this means we can get the outlet to a safe position.

Can someone advise me on what lies behind the various clearance rules - is the position of the outlet the key thing, or is there also a concern about the proximity of the flue to any combustible materials anywhere along its length?

 

[picasso]

need the boiler model first.

 

[Agile]

That type of flue is not a big problem and should only be at least 25 mm from anything combustible.

The limiting factor may be the maximum flue length the boiler can accommodate.

And the availability of flue parts of course.

Where it discharges is also tightly controlled and the most important is that its at least 300 mm from any opening into a house.

Tony

 

[nick60]

OK, my neighbour has lent me their boiler manual with all the info.

It's an Ideal Classic NF60, fan assisted blah blah. It says flue lengths up to 3m are permitted. I realise that elbows increase the effective flue length, but given that the boiler sits directly behind the current outlet I'm hoping there is no problem on that score. The thing that is not so good is the age - the manual is dated March 1992. The flue outlet looks pretty much like zillions of others I've seen but no doubt the devil is in the detail. Any thoughts folks? TIA