Advice please - damp patches on ceiling

[BoatyCath]

Hi all,

Looking for some advice on how to fix the damp patches that have appeared on the ceiling of our narrowboat over the last couple of months.

See the attached pic - they're in several corners of the ceiling panels, mainly in the bedroom and a bit in the bathroom. 

Although the roof needs a coat of paint there are no obvious leaks. The boat has polystyrene insulation with heating on most days and plenty of ventilation.

Any suggestions on what might be the cause, and how to fix without refitting the whole boat (not an option!) much appreciated.

Many thanks,

BoatyCath

[Richard10002]

Can you provide a photo from further away, so we can see the whole of the ceiling and which part of the boat it is. An external photo of the roof in that area would also be good.

Water is coming from somewhere... probably sleeping in, rather than something obvious.

[rusty69]

Our boat has u shaped channels welded to the roof inside with wooden battens to enable the ceiling panels to be attached. These metal channels are insulated with rockwool to prevent condensation forming.I wonder if some of your insulation is not in good contact with the steel in places.

There is no easy way to find out,apart from removing some woodwork.I wonder if the piece of hardwood in your pic could be easily removed with a view to looking between the two  pieces of ply (assuming they are joined at this point).

The only other thing I can think of is an external leak through a vent.Sorry.

Not much help.

Edited February 22, 2018 by rusty69

[Ex Brummie]

It looks like leak and the water has run to the first obstruction (a roof noggin?). Check all roof fittings for vents etc. forward of the stains.

[Alan de Enfield]

Well it is 'water damage' so accepting that there are really only two possible sources for it being in the roof lining :

1) It has come in from outside, or

2) It has come from the Inside.

 

Looking at 1)

The most likely cause is dried 'mastic' around the ventilation mushrooms, which has lifted and allowing moisture to creep under and get between the steel roof and the wooded roof lining.

Other possibilities could be a similar cause but via aerials, chimney hand rails etc.

Unlikely but possible is rain bouncing on the roof and getting in under the mushroom - but - that normally results in drips into the boat rather than into the roof void.

 

Looking at 2)

Only one possibility - condensation. Polystyrene is a rather old fashioned and inefficient insulator and unless all of the joints between the sheets/pieces are taped up the warm air will get between the sheets/pieces, hit the colder steel of the roof and condense.

If this is the cause, the hotter you have the boat (the more you have the heating on) the more likely it is to get worse and worse.

 

Hopefully it is something in option 1.
careful removal of all external fittings, re-bedding and re attaching should at least ensure that that possibility is removed.

The actual leak is unlikely to be anywhere near the wood staining, the moisture will run a considerable distance before it 'collects' against some obstruction, it will then start to leak thru' and rot the wood.

Condensation can result in a "lot" of water (even pints per day).

 

Is this a new problem ?

Did you have it last year ?

is the boat new to you ?

Was there any sign of staining before this Winter ?

Edited February 22, 2018 by Alan de Enfield

[Stilllearning]

I suspect it is condensation, looking at the picture. Having as much of a through draught as possible may help, but I do appreciate that this can be a problem in the winter.

Equally, if there are roof vents, make absolutely certain that there are no leaks from their bases, as that is another common way for water to get in.

Edited February 22, 2018 by Stilllearning

[peterboat]

I had that on my old boat with polystyrene insulation I ended up with the ceiling down to fix it, water vapour was hitting the steel and condensing causing big wet patches, I used sprayfoam and vapour barrier to do the fix, also make sure you have liners in the mushroom vents to restrict warm wet air getting to the roof void, it might help for the moment

[Bee]

If its a steel top then it is unlikely to be leaks through the top. Condensation is a real sod and is not easy to fix. I fear you may have to remove stuff to get at whatever lies behind. Apparently it is possible to buy those little camera things on bendy stalks that they use to spy on birds in nests and things. Could be worth a try but to be honest I think you are going to have to drill holes and at least try squirting foam in to the voids somehow. If you get a hole cutter and a piece of matching ply it could be possible to make a reasonable job of hiding the work but when I had a problem like this I ended up taking the lot off and re insulating the roof. Fingers crossed.

[jddevel]

44 minutes ago, Bee said:

Apparently it is possible to buy those little camera things on bendy stalks that they use to spy on birds in nests and things.

I have a Snap-on camera which is a great help in getting to see out of the way spots. It would require a small hole - around 10mm diameter which I`m sure with a little lateral thinking could later be "plugged or camouflaged " They can be hired.

[bizzard]

The roof space could be insulated with electric blankets £15 on ebay. They only use about 40w each. A smallish inverter would work them. You can get 12v ones too.

[Taslim]

My money is on condensation.

I had similar symptoms in the truck and lifting a panel showed serious lack of insulation.

My 'short term' solution was to drill a grid of holes and inject foam gunge.into one 'till it came out of the next.  The idea was to delay a refit.

It's delayed it for six years so far.  Life's good.

[system 4-50]

If you inject foam practise on a spare bit of ply first. It does not travel horizontally as far as you might think, and it can expand sideways and prize boarding off the surface if you are not careful. But it is a good technique when done right.

[BWM]

All of the above. Condensation following a metal bearer seems likely to be the source, the visible beam is almost certainly fixed to it. If you really don't want to strip the lining off to insulate properly, then as suggested by others you would need to drill through the plywood AND penetrate the polystyrene and inject spray foam behind it. Releasing the foam slowly from the can will allow it to travel further. It may be that the main portion of the roof is well insulated and a few small areas are not, these will act like a magnet for any condensation. 

[Neil Smith]

Condensation will run down the ply to the joint then wick up through the end grain and become visible like yours is.

Neil

[BoatyCath]

Thank you all for the advice and suggestions. We got the boat last summer and there were no previous signs of staining, but I suspect it hadn't been used much in the winter. We'll check all the points suggested then decide the best way forward.

BoatyCath

 

 

[WotEver]

8 hours ago, BoatyCath said:

Thank you all for the advice and suggestions. We got the boat last summer and there were no previous signs of staining, but I suspect it hadn't been used much in the winter. We'll check all the points suggested then decide the best way forward.

BoatyCath

A couple of those salt based dehumidifiers that you can get from Wilko’s and the like, placed in the bedroom, won’t do any harm and may alleviate the problem somewhat. 

[Phil Ambrose]

27 minutes ago, WotEver said:

A couple of those salt based dehumidifiers that you can get from Wilko’s and the like, placed in the bedroom, won’t do any harm and may alleviate the problem somewhat. 

Or even better get some silica gel based dehumidifiers; they really can  help in some cases 

Phil 

[WotEver]

9 minutes ago, Phil Ambrose said:

Or even better get some silica gel based dehumidifiers; they really can  help in some cases 

Phil 

Perhaps that’s what I meant

[Phil Ambrose]

3 minutes ago, WotEver said:

Perhaps that’s what I meant

Maybe, but Wilko do sell a wide variety of stuff so it wouldn't surprise me 

Phil 

[WotEver]

4 minutes ago, Phil Ambrose said:

Maybe, but Wilko do sell a wide variety of stuff so it wouldn't surprise me 

Phil 

I know some friends had a couple of plastic things bought from Wilko that pulled an awful lot of water but I’m not sure what was in them. 

[Phil Ambrose]

Silica gel will pull a lot of water and the crystals change colour when they become fully loaded with water. The advice is to dry the crystals out in an oven till  they return to the original colour but I've always thought that advice has a flaw in as much as it releases the moisture back to the atmosphere .

Phil 

[WotEver]

1 hour ago, Phil Ambrose said:

Silica gel will pull a lot of water and the crystals change colour when they become fully loaded with water. The advice is to dry the crystals out in an oven till  they return to the original colour but I've always thought that advice has a flaw in as much as it releases the moisture back to the atmosphere .

Phil 

Simple solution... use someone else’s oven...

[BruceinSanity]

2 hours ago, WotEver said:

I know some friends had a couple of plastic things bought from Wilko that pulled an awful lot of water but I’m not sure what was in them. 

The simple ones seem to be calcium chloride. When siting one, remember that you have to be able to lift it out with the bottom half full of water without dropping it and spilling it, taking you back to square one.

Dont ask me how I know this...