Boiler flue through roof - how to cut tile?

[Luke]

Hi all, What's the best way of penetrating the roof in order to install a boiler flue? My roof is standard pitched roof with concrete (I think) tiles.

The boiler is a Vaillant Ecotec Plus using a standard flue. I have got one of those flexible flanges to wrap around the tiles and form a seal.

I'm hiring a roof ladder for tomorrow with a view to *somehow* making a hole in a nominated roof tile and then sliding the new flue down from above, according to the instructions that came with the flue.

What is unclear is a suggested means of cutting said hole. Some sort of grinder? Large hole cutter? Stitch-drill?

Thanks in advance.

Luke

[Ronald Raygun]

How about *not* drilling it? Take a tile out and make a new one which has the hole already in it. If as you say it's concrete, you can mix up the cement for it yourself. You can use the old tile as a template to make a mould out of cardboard or something, lined with tin foil or clingfilm or wax paper. Also put an "island" in the middle of the mould where the hole is going to be. This is probably best made out of plasticene or play dough. If the flue is going through at an angle, the hole will need to be elliptical and by using flexible material for the plug, you can slope its sides the right way.

[Vortex7]

I would go to a reclamation place and pick up an identical tile and do some experiments. Clay ones are very easy to drill/saw so long as you are careful...dunno about concrete.

[stuart noble]

Your emphasis on the "*somehow*" suggests it might be a g-s-i (get someone in) job :-) Probably an hour's work for a roofer and his mate. I wouldn't fancy it, and certainly not without an extra pair of hands.

[Phil]

Chain drill with 6mm masonry bit not on 'hammer'. Or diamond core drill - again not on hammer! There are outfits that do diamond core drilling that would no doubt do it reasonably cheaply if you took the tile to them.

Phil.

[Jim]

Your problem will be flashing around the hole in a fashion which doesn't lead to a leak developing in the future.

I think your best option would be to remove a tile (or a couple of them), and put in something like this:

replace the tiles on top.

This would require a collar around the chimney that is supplied from the boiler manufacturer to fit outside the flashing piece. You may want to check that this means the flue terminal is far enough away from the roof when this is done - AIUI there are building regulations for it and it would be affected by the angle of your roof pitch.

[The Natural Philosopher]

remember that a tiled roof is usually THREE overlapping tiles thick.

And you nee some quite delicate leadwork to seal all the layers when you punch through.

A simple collar make not be adequate.

This is a not trivial problem.

[The Natural Philosopher]

No. that way water will slide down thee lead and under the tiles.

As I said, its not trivial to achieve this. Look at the way a chimney stack is flashed in with separate soakers under each tile.

You need lead _under_ the higher tiles and _over_ the lower ones.

This is a pretty good diagram of how to use a product like that.

part suits a single overlapped tile setup: but it will be tough if its a double overlap. It is possible as the site I linked to shows, but there are things to be done. Note the anti capillary stuff etc etc.

[Jim]

>>>>> Then replace the tiles on top.

Perhaps I should have said "a few" rather than "a couple". In any case, I agree, that is exactly what I meant.

>> That part suits a single overlapped tile setup: but it will be tough if

[Phil]

Thinking laterally (!) - go out through the wall, 90 deg bend, and up up up.... saves penetrating the roof.

Phil.

[The Natural Philosopher]

flues never should have 90 degree single bends.

[Jim]

It's a balanced flue for a condensing boiler, though - in fact there are many options as described in this PDF:

[Rick Hughes]

you don't

use a lead collar instead of tile, or a purpose made tile with collar

[Dave Liquorice]

Unless it's a pretty small dia flue and the position is exactly right it won't penetrate the roof through a single tile. See other posts about the grommet/flashing required and how that installs.

There are BR's about the required clearance from the vent and the pitch/apex of the roof. They are many combinations but on a simple pitched roof the bottom of the terminal must be more than 1.5m horizontally from the roof or over 600mm above the apex. I suggest you go off to check those figures as my memory might be faulty.

[Phil L]

Don't even attempt to try and make one yourself. Ask in a local builders or roofing merchant and they will point you in the direction of someone who makes them for you - it's just a normal roof tile which has a hole cut out and a collar set into it with epoxy, last time i got one they were about £8.

You'll need to find out which tile it is first though - different profiles etc.

The tile goes on, then the flue is pushed through, then the rubber flange goes over the top to seal.

PS, I wouldn't bother hiring the cat ladder until you've ordered the tile - it may take a few days

[brass monkey]

The chaps who fitted my boiler simply removed a tile, showed it the angle grinder (square cut-out) then replaced it and added the lead 'skirt' or whatever it is. Maybe they were lucky in that it only spanned one tile.

[dennis]

They probably adjusted it to fit, two bends and a bit of pipe. It adds about £100 to the cost depending on the type of flu (sniffle).

[Luke]

Hi everyone and thank you all for your comments and advice. I must admit I had a sleepless night last night worrying about all the various problems and impossibilities I might encounter. Anyway it was fine. I ended up:

1. Hiring a roof ladder and transporting it back home 4 miles on a pushbike (not recommended)
2. Rigging it up to the roof. Hardest part was hoisting the roof ladder up into position. Not nice up a ladder.
3. Ascending the roof ladder and removing the required tile. Not difficult at all.
4. Cutting out a square hole in the tile using an angle grinder. Got through 4 cheap grinder discs.
5. Putting the tile back in place. Offering up the lead flange.
6. Wrapping the lead flange under the tiles above, below the tiles below, and underneath one of the tiles to the side (basically following the existing tile pattern)
7. Dressing it down with a rubber mallet.
8. Inserting the flue from the top. Securing it from the loft space using bracket.
9. Removing ladders etc from roof.
10. JOB DONE!

The comment about building regs worried me a bit but I have found this only applies to class 1 flues. Class 1 is where the expulsion of the flue gasses is faciliated by the "draw" of the chimney hence the need for clearance above roof height. As this is a fan assisted boiler flue then these rules do not apply. Certainly there was nothing in the boiler doco that suggested any distance limits when installing on a pitched roof.

Anyway here is an FB (public) link to the end result, see

[Ronald Raygun]

Congrats.

I'm interested in why this wasn't difficult. Weren't the tiles nailed down?

[Dave Liquorice]

It's very common not to have every tile nailed, particulary with those interlocking concrete things, maybe every third one is nailed. Now if the place was in an exposed location subject to the full force of incoming gales or storms they would all be nailed.