A puddle in my fireplace

[michael]

I’ve recently noticed a small puddle of water forming in an unused fireplace every time it rains. It could have been happening for a while but I’ve only noticed it recently whilst I’ve been decorating in that particular room.

The chimney stack has two chimney pots, each with a terracotta vented cap and these serve two small cast iron fire places one on the ground floor and one on the first.

The first floor fireplace appears to be perfectly dry whilst the ground floor fireplace is collecting the puddle of water. I wouldn’t have been surprised if the chimneys were open but considering that both pots are capped, I’m not sure how the water is coming in. Could it possibly be a fault in the pot bedding?

I had the caps installed about two years ago by a builder and he seemed to think at that time that the bedding looked pretty sound.

 

[DJH]

It's common for cement flaunching around chimney pots to crack where it meets terracotta flues and with all the rain over the Summer I wouldn't be surprised if water is getting in at at this point.. You don't say if your chimneys are lined with clay pots or not or if you have a damp course built into the chimney stack. When flues are joined to use one stack the first floor flue is usually offset to meet the flue from the ground floor fireplace which would possibly be straighter.

It could be that water is getting in to both flues but is not showing in the bedroom fireplace because the offset is soaking it up whereas in the straighter flue the water will drip more or less directly downwards forming your puddle. Is there any sign of dampness at the ceiling in that bedroom or in the roof space?

Doug

 

[michael]

Thanks for your response DJH. There does unusually appear to be an offset in the ground floor flue evident from the corbeled brickwork above the fireplace in a nearby overhead cupboard. The 1st floor flue however appears to go straight up to the stack. The ceiling above the first floor chimney dose feel a little damp but I’m not sure if this is just because it’s a cold unused and unheated 1st floor room. The slate roof above this was relayed about five years ago with a breathable membrane underlay and new lead flashings were installed at the base of the stack between the stack and the slate roof (Is this what you mean by damp course?). From what I can see, the flues are not lined, just bare brickwork and lime mortar.

I found a fresh puddle of water in the ground floor fire place today despite the fact that we haven’t had rain for a couple of days. Either that or it’s the same puddle that hasn’t evaporated away yet. I‘m beginning to suspect that the water could be condensation dripping down the flue. Both the ground and 1st fire places are those small victorian? cast iron surrounds with a built in metal hatch over the grate that allows you to open or close the flue. As both of these fire places are unused, I tend to keep the hatchs open to allow plenty of ventilation up the flue. As mentioned both chimney pots have ventilated caps.

Both the open hatch and the grate on the ground floor fire place has a wet patch where water has been dripping on it and this surely would have evaporated away by now particularly seeing we’ve had no rain for a couple of days. We have however had quite cold weather recently and the radiators in this ground floor part of the house come on for about a couple of hours in the morning so that we can use a nearby bathroom. I’m wondering if the warm air from the ground floor rooms is going up the cold ground floor chimney and causing condensation on the flue offset.
Is it normal for condensation to form in a ventilated chimney? Should I perhaps close the fire place hatch or would blocking this ventilation do more harm than good?

I’m rather hoping it is just a condensation problem and that it can be easily resolved. The latter i.e. accessing the flaunchings sounds like an expensive access problem.

 

[GRB]

Michael, I had a similar puddle on a hearth stone in an upstairs room when it rained. We had a round chimney pot which we had capped with a round ceramic flue ventilator (the type with the holes in the side) and eventually after a lot of head scratching we traced the problem to the ventilator. What was happening when it rained was water ran down the sides of the ventilator and in through the gaps between it and the pot and was dripping in to the flue. So the problem really was just an ill-fitting ventilator and was put right by a new cowl. However our flue was straight down.

This puddle was not to be confused with the one I found in the bathroom this morning which my 3 year old son was responsible for....

 

[michael]

I think I’ve found the problem.
Looking up through the flap of my little cast iron fire surround with a torch, I can see into the brick fireplace behind which narrows off to the brickwork flue above. Sticking out of the flue is about 6” of circular metal flue liner from which the drip is coming.
It would seem that something was once connected to this flue liner which was removed and replaced (for decorative effect) with the non- functioning fire surround.
I’m pretty sure the dripping water is condensation forming on the cold metal flue liner, a constant drip, which forms a puddle on the hearth.
Not sure what to do about this. I don’t think closing the fireplace flap would make much difference as this part of the house tends to suffer from condensation generally despite keeping all the rooms relatively cool. Even first thing in the morning when the rooms have been unoccupied and the heating has been off all night there are still puddles of condensation on the windows.
I generally put the heating on for about an hour or so in the morning but the condensation remains much the same throughout the day and I’m sure the warm air doesn’t improve the situation.
Any suggestions please other than a mop and bucket

 

[discobarry]

Wellllllll, Since the stoves have been installed at ours(a month or so) we haven't had any problems until a raging westerly came last night and leaked a lot....

I guess the water has come in the cowel down the new lining and into the ash pan of the stove which was about 1inch deep so i have cleaned it all out and run up the stove installer who doesn't seem too fazed by it all and asked us to tell him if it happens again. Around the new plating for the flue it was wet around the edges and very wet towards the right hands side like water was gathering above it but nothing is through yet so i dried all the off but i'm worried a lot of water could be waiting to gush down?

I was also thinking could it of been because the downstairs big stove has been on a lot and drying out the stack next to it making moisture come down through the other stack, condensation i guess?

Any thoughts would be appreciated, thanks, a distressed Aron :S

 

[Flyfisher]

One inch of water in the ashpan?

That doesn't sound like condensation to me.

I'd be suspecting a problem at the chimny pot end of things, though it's going to be difficult to check without getting up there to have a look.

Probably not very helpful, I'm afraid.

 

[discobarry]

Fair enough, it rained pretty heavy last night and from a strong probably horizontal westerly so i guess so.