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Sealing a wooden topped roof?


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3 hours ago, David Mack said:

The timber will be permeable to water vapour whereas the grp is not.  So water vapour from inside the cabin will permeate to the inside of the grp (which is relatively cold) and condense, soaking the wood. There is no way to dry it out and hence rot my well occur.

But if you had put the grp on the inside...

Might not be a bad idea to use thin marine ply skin IMO. Takes paint and sealant well, easy to cut, work, bend, fill, repair etc. And in extremis it's somewhat permeable to moisture.

Also helps to backprime the hidden faces of the T&G/timbers, doubt this was done even in the old days, they didn't want to do themselves out of repeat business... :) External cracks where timbers meet may well be avoided with adequate expansion joints filled with modern goop.

Edited by smileypete
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15 hours ago, smileypete said:

Might not be a bad idea to use thin marine ply skin IMO. Takes paint and sealant well, easy to cut, work, bend, fill, repair etc. And in extremis it's somewhat permeable to moisture.

Also helps to backprime the hidden faces of the T&G/timbers, doubt this was done even in the old days, they didn't want to do themselves out of repeat business... :) External cracks where timbers meet may well be avoided with adequate expansion joints filled with modern goop.

Charity Dock used to completely paint the T&G boards with red lead paint before fitting any cuts etc. were painted on assembly

  • Greenie 1
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4 hours ago, Chas78 said:

Thank you for all the advice and suggestions which i really appreciate BUT it has confused me even more now as which route to go down :unsure::unsure:

Why not try a sample of the worst/most inconvenient leaks, then weigh up the effort and results against complete renewal?

Epoxy needs dry wood really but the 5200 and ali tape thing should be OK to do in a dryish spell, maybe wicks, screwfix, toolstation do a polyurethane sealant (moisture cure), they do gutter sealant.

Edited by smileypete
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When I first acquired my boat the super was the same wood with thin sheet cladding and leaked like a cullinder, I stripped off cladding repaired and treated wood put cladding back stuck down with sicaflex,  New joint strips stuck down with sicaflex lots of it, I used handrails  and wedges to force cladding down. NO SCREWS. It fixed the problem until I could afford a new steel super. 

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  • 6 years later...

Just followed up the topic, great advice, and sorry for revive the thread from the undead. I need some advice too.

 

I have a steel hull and a wooden superstructure, and I have the similar issues as chas. This year im stripping off the walls as there were rotten and couldn't be saved. The roof is still in good condition though the GPR layer is peeling off and need to be redone. 

 

I have to decide now if i want to rebuild it on wood or steel, and its a question that got me paralyzed on this part of the project so id love some advice .

 

I became confident in arc welding after burning countless rods in a garage and many youtube videos.  I have weld plates on the hull (its the part where you walk on when moving outside of the boat I keep forgetting its name). In short welding the super on steel it something i can do myself,  but still the cost of the steel is an issue as im on a budget after burning my savings refurbishing my first canal boat.

 

But on the other hand after adding all the the extra money and work that wood tops involve (and countless other products as sealant), this offsets the savings in the wood materials, or correct me if im wrong as i never did fiberglass before. The fiberglass part seems scary at first considering how unpredictable and less than ideal UK's weather.

 

I already started to rebuild the cabin with wood but i think im already changing my mind and it might be still in time to do it in steel. I cant commit to an option so any advice would be appreciated. 

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If you stick with wood or wood & GRP please ensure that the cabin sides fits OVER a steel upstand all around the gunnels. Also ensure the upstand is not perforated. It is a lack of such an upstand and/or rust holes that cause leaks at the cabin side to hull joint.

 

As far as GRP work and the weather is concerned. You mix the resin with a hardener, which may r may not have an accelerator component. You select the amount of accelerator to suit the condition, and to a degree the amount of hardener. For instance, At present I would not be working in full sun, bit would work as soon as any dew had properly evaporated and would use a resin with minimal accelerator. When it started getting warmer, I would probably reduce the hardener in the mix a bit. In cold weather, I would choose a resin with more accelerator.

 

the GRP resin normally hardens within a very few hours or less so it is normally possible to dodge any rain. However, for covering the roof and cabin side I am not sure ordinary GRP using chopped strand mat would produce an acceptable result. Look at an open weave roving and consider using epoxy resin to "paint" it onto the structure.

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A steel cabin is easier than a steel hull, but it still is not a simple task.  Certainly skills beyond welding are essential.

You also need a lot of kit, including a decent plasma cutter for curves and a suitable venue for making a lot of continuous noise.

 

A wooden cabin also requires a suitable venue for much noise and a good selection of tools, but these are at least useful for the fit out.  Tbe traditional route to waterproof cabins is a layer of painted canvas covered by a layer of Masonite. Proper  canvas being hard to get these days I found rubberised bituminous waterproofer to be effective under the masonite and also acted as a glue between timber and Masonite.

 

N

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1 hour ago, Tony Brooks said:

If you stick with wood or wood & GRP please ensure that the cabin sides fits OVER a steel upstand all around the gunnels. Also ensure the upstand is not perforated. It is a lack of such an upstand and/or rust holes that cause leaks at the cabin side to hull joint.

 

As far as GRP work and the weather is concerned. You mix the resin with a hardener, which may r may not have an accelerator component. You select the amount of accelerator to suit the condition, and to a degree the amount of hardener. For instance, At present I would not be working in full sun, bit would work as soon as any dew had properly evaporated and would use a resin with minimal accelerator. When it started getting warmer, I would probably reduce the hardener in the mix a bit. In cold weather, I would choose a resin with more accelerator.

 

the GRP resin normally hardens within a very few hours or less so it is normally possible to dodge any rain. However, for covering the roof and cabin side I am not sure ordinary GRP using chopped strand mat would produce an acceptable result. Look at an open weave roving and consider using epoxy resin to "paint" it onto the structure.

Thank you this is gold. Im in continuous cruising as couldn't find any boatyard yet, all the ones i tried are in full capacity. I wonder if in the countryside id have better luck. Yes, not disturbing anyone was a concern, i always found moorings far away from residential areas or on the opposite bank of the towpath, id cover my work area with tarps to not blind anyone while welding. Fire extinguishers always at hand and a pal as safety lookout. I also managed to cut the 4mm plates with a angle grinder and a jigsaw with metal blade. Not the fastest way but effective.  Walls will not have curves and the supplier i can get the steel from would cut each panel to size.

 

When you said paint with epoxy, only for the cracks and joints or the whole surface? Will resin stick to harden epoxy?

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I had the same problem a few years ago. But it was not an easy or quick fix.luckily like me you have handrails rather than cants that makes it easier. The way I tackled it was to strip the roof down to the bare timber planks and let it dry out. The planking will tend to bow upwards as it dries so sanding will be required.

then coat the roof with west epoxy. You may need more than one coat until you get a hard surface then apply two layers of fibreglass mat/cloth composite impregnated with epoxy resin with the cloth uppermost sanded and followed by an epoxy filler again sanded and the two coats of two pack poly gloss or Matt. This should give you about a 5mm thick roof that will be entirely waterproof, never need painting and be strong enough to withstand any damage.

materials eg 40 litres of west epoxy will cost about £2k but I did this on boat in 2007 and it still looks good. Unless you are under cover you need to do it at this time of year.

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4 minutes ago, Mike Adams said:

 

materials eg 40 litres of west epoxy will cost about £2k but I did this on boat in 2007 and it still looks good. Unless you are under cover you need to do it at this time of year.

Thank your for the detailed step by step. The ripping off part should be easy as the sheets of fiberglass are coming out in a big piece leaving the bare wood exposed.  Epoxy exceeds my budget at rhe moment, would resin provide similar results? I was considering "Cure it"resin as a boater used this product with good results. 

 

Just as reference my roof is 10m2 in two sections, and the walls are approximately 7m2. Im making the bow side half first and then the second.  

 

Thank you again for all the help. 

IMG_20201020_103328_936.jpg

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2 hours ago, Tony Brooks said:

If you stick with wood or wood & GRP please ensure that the cabin sides fits OVER a steel upstand all around the gunnels. Also ensure the upstand is not perforated. It is a lack of such an upstand and/or rust holes that cause leaks at the cabin side to hull joint.

 

How the cabin should be held on the gunnels without screws? With sealant or epoxy? My gunnels doesn't have upstand, only a slight angle. Im still on time to add them thank you.

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24 minutes ago, JaimeManero said:

Thank your for the detailed step by step. The ripping off part should be easy as the sheets of fiberglass are coming out in a big piece leaving the bare wood exposed.  Epoxy exceeds my budget at rhe moment, would resin provide similar results? I was considering "Cure it"resin as a boater used this product with good results. 

 

Just as reference my roof is 10m2 in two sections, and the walls are approximately 7m2. Im making the bow side half first and then the second.  

 

Thank you again for all the help. 

IMG_20201020_103328_936.jpg

-6048776265034488703_121.jpg

 

How the cabin should be held on the gunnels without screws? With sealant or epoxy? My gunnels doesn't have upstand, only a slight angle. Im still on time to add them thank you.

 

I would make the up stands high enough to bolt or screw through into the wood.

 

The up stand is what prevents leaks but to stop water wicking up into the bottom of the side I would bed it on one of the engineered adhesive sealants like Sikaflex or a similar Screwfix/Toolstation product. If you use plywood and do not adequately seal the bottom edge then expect it to eventually delaminate.

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5 minutes ago, Tony Brooks said:

 

I would make the up stands high enough to bolt or screw through into the wood.

 

The up stand is what prevents leaks but to stop water wicking up into the bottom of the side I would bed it on one of the engineered adhesive sealants like Sikaflex or a similar Screwfix/Toolstation product. If you use plywood and do not adequately seal the bottom edge then expect it to eventually delaminate.

Thank you. Yes, the old plywood suffered from that problem, they started delaminating and rotting from the bottom.  Also the gunnels were made of wood causing the whole cabin to sink into the hull and collect rainwater inside, bad combination.  

 

 

 

 

 

 

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38 minutes ago, JaimeManero said:

Thank you. Yes, the old plywood suffered from that problem, they started delaminating and rotting from the bottom.  Also the gunnels were made of wood causing the whole cabin to sink into the hull and collect rainwater inside, bad combination. 

 

FWIW, I expect any plywood will delaminate in time, even the very expensive Robins of Bristol marine ply. One way to extend the life a little and make it look better when that happens is to screw some half round topped timber about 50 to 75mm tall and maybe 10mm thick to the bottom of the cabin sides, again bedded on sealer/adhesive.

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Following a small leak in the roof vent on our campervan I have been introduced to "rubber tool paint" which is easily found and not expensive compared to alternatives (eg strip and rebuild)

 

Designed to coat hand tools with a non-slip 'handle' it is great as a waterproofing / sealing paint :

 

Rubber Coating Dips | Liquid Rubber Dips | Rubberize It! – Rubberizeit

 

An American site, but its the same stuff as I used.

 

 

A UK site :

 

PLASTI DIP the Multi Purpose Rubberised Paint / Rubber Coating - Frost Auto Restoration Techniques

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On 17/05/2017 at 14:03, rusty69 said:

I am no expert on the subject, but think if it were mine, and I was confident the underlying wood was sound and dry, I would remove each screw individually and inject some thickened epoxy in with a syringe and then reinsert the screws.

 

 I'd do the same but I'd use a good PU sealant rather than epoxy which tends not to be that flexible.

 

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

 

I'd key under each screw with a bit of green scourer and clean with a cloth dampened with white spirit before applying the sealant to the screw threads.

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Looking at your boat for the roof a simpler solution might be to use a liquid rubberised coating on the roof. The biggest problem might be the joint between the cabin sides and the steel deck. You need to work out how the cabin is fixed to the deck. As stated an upstand is best but difficult to do without removing the cabin sides.

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6 hours ago, Mike Adams said:

Looking at your boat for the roof a simpler solution might be to use a liquid rubberised coating on the roof. The biggest problem might be the joint between the cabin sides and the steel deck. You need to work out how the cabin is fixed to the deck. As stated an upstand is best but difficult to do without removing the cabin sides. 

The cabin sides are already removed as the frame and the plywood was in very bad condition. Also the frame had many repairs and it was just a stack of timber over more timber so I decided to remove them all together. Then I welded steel gunners to rest the cabin there. My initial thought was to bolt through the gutters to a 2x2 timber that would be the feet of the new frame, and then thin 9mm plywood for the walls as they don't need to carry any load. Also if anything goes wrong i can remove each panel of plywood without compromising the structure.  But after reading Tony Brooks message i think i should weld a up stand and bolted from there.   

 

I forgot to mention the second reason to rebuild the cabin is it only 1.7m of headroom, I'm 1.85 so imagine how uncomfortable and sore my back end up after spending a day inside. Im aiming to have at least 2.0m of headroom, 

 

After watching many videos on YouTube and other topics on this forum ill go for a GPR resin with fibre mats, using fiberglass powder mixed with resin to achieve a peanut butter-like putty and fill any corner and cracks. Ill have to do this job either I choose to do the walls with steel oo wood. I haven't make up my mind yet  but I'm gravitating towards wood (lets see for how long I can stick to it!). If I get savings and access to a boatyard I can always rebuild it for steel in the future. 

 

This is a up to date picture (the pic i sent its almost 3 years old), where you can see the provisional lift of the roof, and the pallets are just for security, if I have to leave the boat id just put many of them to hinder any attempt to break in. I had power tools stolen already, who would guess not having wall was so unsafe? xDD. CTTV recorded everything but didnt do much to keep them from stealing them.  In the pictures you can have a view of the gunners, because I didn't have clear what the material of the cabin would be I made them oversized so I could cut the excess once was done. 

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6 hours ago, blackrose said:

 

 I'd do the same but I'd use a good PU sealant rather than epoxy which tends not to be that flexible.

 

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

 

I'd key under each screw with a bit of green scourer and clean with a cloth dampened with white spirit before applying the sealant to the screw threads.

 

Is this a similar product as sikaflex? 

 

7 hours ago, Alan de Enfield said:

Following a small leak in the roof vent on our campervan I have been introduced to "rubber tool paint" which is easily found and not expensive compared to alternatives (eg strip and rebuild)

 

Designed to coat hand tools with a non-slip 'handle' it is great as a waterproofing / sealing paint :

 

Rubber Coating Dips | Liquid Rubber Dips | Rubberize It! – Rubberizeit

 

An American site, but its the same stuff as I used.

 

 

A UK site :

 

PLASTI DIP the Multi Purpose Rubberised Paint / Rubber Coating - Frost Auto Restoration Techniques

 

Interesting material, I definitely can think of many uses for it. I want to research more about it, but so far the GPR resing seems like the best option. The striping part of the old fiberglass is virtually effortless as its not well bonded anymore (maybe never were? i know some people skip the first layers of resin before lying the mats.  I can remove it almost in a single sheet. 

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The conventional way is indeed an upstand of maybe 2" and the sides are then bolted on to this leaving a gap at the bottom so the wood is not sitting in a puddle. As for the roof I would use decent roofing felt, overlap the sides and protect that edge with a wood strip. when it wears out just re do it.

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4 hours ago, Bee said:

The conventional way is indeed an upstand of maybe 2" and the sides are then bolted on to this leaving a gap at the bottom so the wood is not sitting in a puddle. As for the roof I would use decent roofing felt, overlap the sides and protect that edge with a wood strip. when it wears out just re do it.

Sounds like a good idea. Also i was having troubles with the 2x2 for the structure as the gunnels are at an angle and that would involve the timber that sits on top to be planned. I can weld the upstands at the angle i need so ill have less angles to worry about on the timber.

 

Also leaving that gap sounds like a great idea. I guess something like 20 or 50 mm will do gor this gap? Also ill fill that gap with sickaflex to allow some expansion. 

 

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