Another crazy leak

[Burnsy]

I have just installed a fireplace into our new house. It is a stand alone unit that has a 150mm stainless flue runing right up. Once it gets to the ceiling there is a 200mm then 250mm galvinised heat shroud running right through the ceiling space (only 300mm in this case) then out through a tin roof. the outer shroud protrudes through the ceiling into the room by about 200mm. The 250mm shroud is sealed with a dektight rubber seal that is tekked to the roofing tin. This is then sealed with silicon right around the shroud and against the roofing tin, and heaps of it. A weather cap then slots into the stainless flue and over the outer shroud - clear as mud right!

The leak is dripping from the heat shroud that protrudes into the room straight down onto the heater. We have had some pretty extreme weather here for the last week but I am stuffed if I can find where the water is getting in. The weather cap seems well designed and I can not see how water is getting through this, I thought it may be leaking through a seam in this but I ran a bead of muffler sealant around it and it is still leaking.

Anyone had a similar problem or can shed some light?

[Bloss]

My guess would be that it is water being blown in under the weather cap and then rolling down to the room below.

Most caps nowadays do not go out wide enough or down sufficiently low. It is always a compromise as you want the smoke to be as unrestricted as possible while stopping any water influx.

As a test you could place a temporary extension lip around the weather cap using a strip of aluminium flashing fixing would depend on the cap type, but remember it can get very hot so gaffer tape might not be the best choice.

Leave it on until you have some similar storms or rain events and see what happens. If it fixes the problem you can make up a permanent solution using gal - or simply buy and fit a larger cap.

Sometimes this sort of occasional leak that occurs only in windy storms can be fixed by simply lowering the cap - by bending the brackets so it sits lower or removing and reaffixing the brackets at a lower position.

You no doubt know this, but roofs are dangerous places so 'be careful out there".

[Cliff Rogers]

Also check the vertical join in the outer shroud.
If it is a roll folded join, water could be getting via capillary action.

[silentC]

If you have a join above the dektite, make sure the outer flue is lapped the right way. The one below should be inside the one above.

[Burnsy]

Thanks for the possible solutions. I don't think it is the hat as it has a vertical shield around the hat to stop blow in and I also sat a bucket over it for the day and still got some water in. I did look at the vertical joint (fold/roll) and thought nah it can't get in but maybe Cliff is right, I will run a bead of sealent down it and see if it helps.

There are no joints above the dektite so it can't be that. This really does have me stuffed as I have used half a tube of silicon up there and it still leaks, visually you look at it and think no way that will leak. I will get a phot if I get home early enough tomorrow.

I was doing some thinking on the way home and thought I might tie some rag around the shroud where it protrudes through the ceiling because if that stays dry it will confirm that the water is getting in above the dektite. I also have not been able to find any moisture in the ceiling but it is sealed ply so would probably take quite a bit.

[Cliff Rogers]

We had a leak that was there when we bought the house, I poured silicon all over the place & it wouldn't stop til I got up on the roof & spend about 3 hours removing all the old silicon & shrubbing to metal clean & then starting again.
One of the previous owners had put sealent over a patch of mould & it was seeping in under it.

[Burnsy]

We had a leak that was there when we bought the house, I poured silicon all over the place & it wouldn't stop til I got up on the roof & spend about 3 hours removing all the old silicon & shrubbing to metal clean & then starting again.
One of the previous owners had put sealent over a patch of mould & it was seeping in under it.

This is all brand spanking new, that is why it is driving me nuts. I think I need to ascertain exactly where it is coming from (inside or outside of heat shroud) before going any further.

[Skew ChiDAMN!!]

Did you run a bead of silastic under the lip of the dektite before fastening it down?

(I also like to run a bead around the very edge of the hole first, and let it go off before installing the dektite. A bit like folding the edges of the hole up, but a lot quicker and it will last as long as the dektite will... )

[Burnsy]

Did you run a bead of silastic under the lip of the dektite before fastening it down?

(I also like to run a bead around the very edge of the hole first, and let it go off before installing the dektite. A bit like folding the edges of the hole up, but a lot quicker and it will last as long as the dektite will... )

Unfortunately no. I have in the past but my chippy had aready put it down by the time I got there and said "no need I never do it". I don't think it is leaking under the dektite though as if it was it would be dripping off the roofing iron onto the ceiling not dripping of the heat shroud that protrudes through the ceiling as there is 30mm clearance between the shroud and the ceiling. Also, I have been up there when it rained hours earlier and the dektite is still holding water in the corrugations so it is not seeping in under it (probably because of the 30 mm of silicon that has been run along the join).

[rat52]

this may sound obvious but have you checked the screws securing the decktite

I have always siliconed under the flange inside the line of the screws.