Log Burner Flue issue

[Meltham Terrier]

Hoping that someone may be able to assist with an issue that happen this morning.

My daughter found water/condensation on the ceiling of her bedroom. The flue for the log burner runs up the outside of her bedroom wall.

When I looked outside I noticed a water mark on the stone work directly under the where the flue comes through the outside wall.
The distance from the edge of the wall to the flue is 3m which is about the same distance we have water damage in the bedroom.

Question is , is this a repointing job around the flue or could it be something more.

The fire was serviced a few weeks ago and the flue swept and a bird guard was also fitted.

Thanks Andrew.

[KAgantua]

Is top of the flue capped?
If not could be rain going in and coming out join at the bend

[Meltham Terrier]

Yes the top of the flue has a cap

[Magooagain]

Water is coming from somewhere obviously. Is that flue insulated?ie double skin. Could be condensation within the flue or it s rain getting in somewhere. Looks like there s history of it running down the outside of it by the look of the green on the walls.

Edit to add that the first photo looks as though the external surface water could capillary into the house.

Edited by Magooagain on Sunday 26th October 12:37

[OutInTheShed]

Judging by the green stain, water has been dripping from there for a while.
Have you been using the fire a lot in the past months?

Do you burn a lot of damp wood?
Do you run the fire very low for long periods?

The dew point of a wood fire should be quite low, maybe 50deg C.

I think it needs a proper looking at, either the flue is damaged and/or a lot of rain is getting in.

[GasEngineer]

Can't really tell from your pictures but does where the flue goes through the wall look something like this:

[Pitre]

It looks like all external rain is running down the flue and seeping into the wall. An arrangement like the photo immediately above would not only fix the problem but make sweeping it much easier.

[Meltham Terrier]

We have been using the fire more recently but we only have been using it for 3 or 4 days per week and usually for a few hours each day.

We do leave the fire to burn out when we go to bed.

We never burn wet wood only kiln dried.

Yesterday the fire was lit for around 5-6 hrs.

[JoshSm]

Is it water coming from the flue, or just rain/condensation runoff from the outside?

I suspect the latter in which case you need something to form a drip edge. It's not an uncommon issue. Could try some flashing or put something around the flue itself to make it drip.

Filling the crack in the pointing with some mastic or silicone would help stop water tracking back through the wall but first you want to stop it reaching the wall in the first place.

[Crumpet]

I’d go with penetrating damp from rain running down and off the bottom side of the flue and then making contact with the stone and mortar. Strange that it’s passed through the cavity, though. Unless the fitters have bridged it with the mortar when they fitted it or it’s weeping back along the flue within the cavity?

[OutInTheShed]

Crumpet said:

I d go with penetrating damp from rain running down and off the bottom side of the flue and then making contact with the stone and mortar. Strange that it s passed through the cavity, though. Unless the fitters have bridged it with the mortar when they fitted it or it s weeping back along the flue within the cavity?

It's not really strange that it passes through the cavity, because the flue will slope through the cavity, higher at the outside.
but there looked to me to be water dripping out of the mortar where at the bottom of the flue in the first picture, and a green stain suggesting long term seapage from here rather than just when raining?
It looks like water is coming out here, not going in, but one picture can be deceptive.

It's a st job of work, there should be something to prevent this other than a crude mortar-metal joint.
Maybe a drip rail or other feature so rain running down the outside of the flue drips off instead of running down the wall?
Maybe a more effective seal between flue and wall? But this would still tend to create a stain.

But I'm not convinced this is the only problem, it sounds like a lot of rain getting in to create the problem on the ceiling.
OTOH, we've had some epic rain lately...

There is a limit to what can be diagnosed from a couple of pictures on the interweb.
I'd suggest getting someone competent to look at it in real life so to speak.

With that amount of wet, the flue could be rusted and dangerous.