Expansion along woodburner flue

You probably need some on site advice from a heating engineer who has the appropriate professional qualification. If you don't then expect your insurance to be invalid if the worst happens.

/ . If you don't then expect your insurance to be invalid if the worst happens./q

Woe woe & thrice woe......

Jim K

How far above the roof is the "top hat"?

Jim K

Doesn't sound right. I'd expect the flashing to stay with the roof and be slighly clear of the flue. Attached and sealed to the flue is a storm collar that overlaps the top of the spigot of the flashing.

Scroll down to the flashing kits at the bottom of the page.

And this is the point where photos would be REALLY useful, isn't it?

External overview (cold) -

External closeup (cold) -

External closeup (hot) -

Inside view -

- the bracket's on the double-skinned flue

Are you in a smokeless area, I saw on the tv the other day a guy was informed that due to it not being designed to pass smoke free legislation he could only burn smokeless fuel on his woodburner, which kind of defeated the object of having it in the first place! Brian

Agreed.

Er the corrogated flashing in the best part of an inch above the corrogated roof. You must live somewhere where the rain only ever falls near vertical, up here it frequently falls near horizontal so much so that vertical is note worthy. B-)

Half decent bit of wind and rain blowing up that roof will get in through that huge gap.

The roof will be pretty cool.

No, the flashing up stand needs to be freed from the flue with as little clearance as possible and all the flashings put back down properly and snugly. The storm collar then needs to be positioned just above the top upstand with the system cold.

I very much doubt it. Rural Herefordshire.

That was my thought... Fortunately, the prevailing weather tends to come from the west, the side that's tucked under the roof edging.

Thanks. Time to get up onto the handily-placed shed roof (right next to that flank of the building, and solid enough to walk on).

From the photos, the shed has been re-roofed, retaining the chimney flashing.

As has been said, there should be a gap between the sleeve and the flue. Maybe the flue has also been re-newed and forced to fit.

I guess down there you don't get fine dry powder snow. That's right bastard stuff for getting in. It gets carried on the airflow(*) and as the inside of a building tends to be at a lower pressure than the outside when the wind blows due to venturi effects it gets drawn in rather than blown.

(*) So can follow quite long and twisty paths.

No snow at all last winter - our first one here. But nothing would surprise me about the climate here.

Yep, early this year, replacing knackered asbestos-cement corrugated sheet.

The flue's not been touched since installation, somewhere between '98 and '05 or so.

chimney

The flashing will have been. How did they get that new roof sheet in place without taking off the flashing and possibly the top section of flue?

Suspect when they put the flashing back they formed it tight to the flue or perhaps even sealed it with silicone...

I've finally got round to climbing up there and having a good look.

The rain collar is firmly glued to the flue using a grey sealant/mastic of some kind. The bead above has been nicely smoothed in, so it almost looks like a weld.

There's also a sodding great big bead below, which does a great job of firmly attaching the flashing to the flue, too.

There's the problem, but how to get that freed off? No doubt the collar was nicely fitted after they'd done a good job gooping up the top of the flashing spigot. As that's tucked up under the storm collar a right B to get at.

Or do you mean there is a bead of sealant underneath where the collar meets the flue? It might be possible to get a sharp knife and cut through the bits that are stuck to the flashing. Maybe also along the slope of the storm collar then pull it out. Depends how much of this selant bead is stuck to the flashing.

Or take a hacksaw to the whole lot just below collar and replace the top section of flue and fit new storm collar.

I do.

Reminder of the view...

That's kinda tempting. There's a joint between flue sections just below the roof.

I'll pull it off, get it down to ground level, and have a rummage.

Don't black tin roofs get warm in direct sunshine?

So I went around the collar with a Stanley knife, and freed it. Then between flue and flashing with the knife, and freed that. A good bead of sikaflex around the flue, just above the flashing, and lower the collar to that. Then a bead around the top, and smooth. The flue still moves relative to the flashing, and it looks like it should be watertight.

I'll give it 24hrs, then fire it up and see what happens...