External roof vent covers / sealing

[Nemysys]

Hi all

 

Any suggestions on the best way / product to seal the external roof mounted ventilation covers. They are about 10” diameter with 8-10 screws holding them down.

Before anybody mentions it, I’m not looking to block the vents, just to seal around the edges as I believe rain is seeping underneath and getting inside.

 

I had seen a ‘squeezy’ instant silicon gasket sealant, comes in a tube a bit like the sealant you would use around your shower.

Thought was to remove the vent cover, run a ring of this around the outside, just outside the screw hole ring and then screw them back down.

 

Thoughts?

 

Darren

[Tracy D'arth]

Are you sure that they leak? It could be condensation on the underside dripping in. Always very possible in the present wet cold conditions.

[Alan de Enfield]

You could try "Captain Tolley Creeping Crack Cure", simply dribble it around the rim and it will dissapear underneath and form a waterproof seal.

 

[Nemysys]

21 minutes ago, Tracy D'arth said:

Are you sure that they leak? It could be condensation on the underside dripping in. Always very possible in the present wet cold conditions.

We are currently refitting the boat, and have witnessed leaks through screw holes etc.

Understand what you say about condensation, but this is noticeable when it rains.

 

There has been minimal maintenance done to the vent covers over the last number of years, so to protect the new interior was looking to do some external maintenance, looking for suggestions on how best to create a waterproof seal.

[Tony Brooks]

As I can't see the covers so don't really know what you have I assume they are similar to the flying saucer vents many hire boats have. If the screws you talk of are self tappers I would drill and tap the roof and cover to accept machine screws and use a sealer on the threads. I would do the same if the vents are mushroom vents using a flange onto the roof.

 

Remember Photos  allow everyone to understand what you are talking about.

[Mad Harold]

They need to come off for cleaning the joining surfaces.Capt Tolleys is good,but only for small gaps.Domestic silicone sealer is no good on a boat,it won't last very long.

I would use non setting mastic or mastic tape to re seal.

[Tony Brooks]

Probably better to use sealer/adhesive like an EBT or simmilar

[MarkH2159]

I have used this product for both sealant and adhesive, perfect for vents too.

 

Everbuild Stixall Extreme Power https://g.co/kgs/kAEvz2

[Nemysys]

3 hours ago, Tony Brooks said:

As I can't see the covers so don't really know what you have I assume they are similar to the flying saucer vents many hire boats have. If the screws you talk of are self tappers I would drill and tap the roof and cover to accept machine screws and use a sealer on the threads. I would do the same if the vents are mushroom vents using a flange onto the roof.

 

Remember Photos  allow everyone to understand what you are talking about.

Sorry, no decent photos of the vents, maybe you get a clue from this zoomed in image.

 

yes, they have a flange around them with self tappers.

 

[Tony Brooks]

Yes flying saucer vents. You have two things to seal. The screws that hold the metal outers to the roof (the ones I replaced with machine screws with sealant on them) and then the plastic vents that will be exposed when you remove the cover.

 

Make sure the little drain channels that are formed but bumps in the circumference of the cover are clean and free draining. If they are not the covers have been known to fill with water and overflow into the plastic vent. Do not try to seal the outer cover to the roof for fear of making the draining worse.

 

The plastic inner seems to have a sort of spongy rubber/plastic O ring in its base that is intended to seal it to the roof but that may have hardened and the plastic the vent is formed from may also have hardened, so the plastic bit may break up as you try to remove it. I think new ones may be available but since EC Smith  wet broke I am not so sure. There is no reason not to use sealer under the plastic bit apart from when you next need to remove it. I think I would just try to seal the screws.

 

Until proven otherwise and without knowing which set of screws are leaking I would tend to suspect blocked drains.

[Sea Dog]

Flying saucer vents don't have a great reputation, hence the move to mushrooms, but you have great advice from @Tony Brooks above.

 

The only advice I'd add is to avoid any product involving silicone as you'll cause yourself future issues with over painting. Stixall is definitely really good, my solar panel brackets are secured with it,  but I don't know whether you'll have difficulty separating the joint in future. I resealed a window last year using neoprene tape and fairing off the gap with some non silicone black goo who's name I'd tell you if my boat hadn't been effectively confiscated by Boris as a result of him locking me up!

 

[David Mack]

12 hours ago, Nemysys said:

Sorry, no decent photos of the vents, maybe you get a clue from this zoomed in image.

 

yes, they have a flange around them with self tappers.

 

I had those on Belfast. Lots of dripping water in the rain. This is what I found when I took them off.

 

[Tony Brooks]

 

Personally I think mushroom vents on the roof of a boat are a terrible idea, it's all too easy to get ropes caught on them. Especially when single handing through locks where you may well be using the centre line.

 

The images shown in David's link look more like insufficient prep and painting before they were fitted and then insufficient maintenance. I would agree if anyone criticise the plastic parts of the actual vent and also the way the plastic lets light into sleeping cabins.

[robtheplod]

17 hours ago, Alan de Enfield said:

You could try "Captain Tolley Creeping Crack Cure", simply dribble it around the rim and it will dissapear underneath and form a waterproof seal.

 

 

This gets my vote just on the name.... Be great to go into a shop and ask for it.....!!

[Tony Brooks]

3 minutes ago, robtheplod said:

 

This gets my vote just on the name.... Be great to go into a shop and ask for it.....!!

 

You can, well at least a chandlers when they are allowed to open. Very good as a temporary seal on windows while you wait for suitable weather to take them out and do the job properly.

[blackrose]

I would take the fittings off, use a small wire brush or a bit of sandpaper to clean both mating surfaces, give both surfaces a quick wipe over with white spirit to clean off the dust and any grease, and then apply a bead of Stixall to the underside of the vent before screwing it back down. I'd probably apply a tiny bit of the sealant to the screws too. After 24 hours it will be cured and fully sealed. Like all PU sealants it will remain flexible like rubber and allow for thermal expansion and contraction.

 

Use vinyl gloves because the stuff tends to get everywhere and clean up any excess Stixall with white spirit and a cloth before it cures.

 

https://www.toolstation.com/stixall-adhesive-sealant-290ml/p77137

 

Comes in black, white or clear. Also available on Amazon, etc. I wouldn't be without it on a boat.

Edited March 13, 2021 by blackrose

[David Mack]

6 hours ago, Tony Brooks said:

 

Personally I think mushroom vents on the roof of a boat are a terrible idea, it's all too easy to get ropes caught on them. Especially when single handing through locks where you may well be using the centre line.

 

The images shown in David's link look more like insufficient prep and painting before they were fitted and then insufficient maintenance. I would agree if anyone criticise the plastic parts of the actual vent and also the way the plastic lets light into sleeping cabins.

Yes they clearly hadn't been maintained for years. But with the outer stainless covers pop riveted to the roof it isn't easy to remove them to clean underneath. Screws would make things easier, but even so, these really need taking apart a couple of times a year as well as when repainting the roof, to properly clean out the leaves, dirt and green growths.

[Tony Brooks]

Funny thing is that ours on JennyB were fine for about 19 years but I am sure the rust goblins were attacking the roof where  could not see it.

[blackrose]

7 hours ago, Tony Brooks said:

 

Personally I think mushroom vents on the roof of a boat are a terrible idea, it's all too easy to get ropes caught on them. Especially when single handing through locks where you may well be using the centre line.

 

That's why you have two centre lines - one going down each side of the roof. Then you never have to flick it over to the other side. To m that was obvious as I'm single handing a widebeam, but it's equally valid on a narrowboat.

Edited March 13, 2021 by blackrose

[ditchcrawler]

25 minutes ago, blackrose said:

 

That's why you have two centre lines - one going down each side of the roof. Then you never have to flick it over to the other side. To m that was obvious as I'm single handing a widebeam, but it's equally valid on a narrowboat.

Same as I have

[Alan de Enfield]

Doesn't everyone ?

 

 

 

[ditchcrawler]

2 minutes ago, Alan de Enfield said:

Doesn't everyone ?

 

 

 

Surprisingly no

[Tony Brooks]

50 minutes ago, blackrose said:

 

That's why you have two centre lines - one going down each side of the roof. Then you never have to flick it over to the other side. To m that was obvious as I'm single handing a widebeam, but it's equally valid on a narrowboat.

 

Also the same as I had but they can still get caught under mushrooms, especially when moving it to pull from the front.

[Alan de Enfield]

4 minutes ago, Tony Brooks said:

 

Also the same as I had but they can still get caught under mushrooms, especially when moving it to pull from the front.

 

 

That's where fairleads help.

[blackrose]

4 minutes ago, Tony Brooks said:

 

Also the same as I had but they can still get caught under mushrooms, especially when moving it to pull from the front.

 

I've never caught my centre lines on mushroom vents either on this widebeam or my old narrowboat. If you have 2 centre lines there's no need for them to be anywhere near the mushroom vents, but I suppose that might depend on the position of the vents.

 

On my widebeam the centre lines go through fairleads on each side which lookslike what Alan's doing in his picture. You can't get the lines caught around mushroom vents if you use fairleads even if the line is going forward.