Waterproofing wooden top steel narrowboat

[Jae]

Hi all,

I'm in the midst of restoring a 1970's wooden topped steel narrowboat. I had hoped to be able to just tidy up (reseal and repaint) the existing original wood in order to stop leaks, but this is looking less and less likely an option as work goes on and I am now looking at skinning the cabin top.

I wanted to ask if anyone had experience skinning a wooden top, how well this worked, how long it stayed watertight, and what might be best to use (canvas/felt/GRP/etc)

 

In the long term, I'm unfortunately probably going to have to bin the original structure and have the top overplated in steel or otherwise replaced. That's not currently a short-medium term option for me practically or financially however so am looking at making the existing cabin top as liveable as possible in the meantime.

 

Any other ideas or suggestions welcome, thanks in advance

[BEngo]

When I over skinned my wooden top Springer I used 6mm oil tempered hard board.  AKA Masonite.  E.g https://www.google.com/url?sa=t&source=web&rct=j&url=https://www.graftonboards.co.uk/Products/Oil-tempered-boards-p142528947&ved=2ahUKEwjk14XZgqj5AhVGQ8AKHaUPDHcQFnoECBAQAQ&usg=AOvVaw1osGJPhFhW-Z0JWYmGyaZV

It was soaked in water for a week to expand it and then fitted wet, fastened with ring shank nails.  Each piece was bedded in a layer of bituminous rubber waterproofer. (A sort of sh!tty brown goop that dried out to a tarry black and stuck like the proverbial to a blanket ).

Joints were sealed with aluminium  capping strips.

 

The Masonite shrank as it dried  and went nicely taut.  It painted up fine with aluminium primer and some decent top coats.  

The whole lot was still going strong 8 years after I sold the boat.

 

N

[blackrose]

I've seen them overskinned in aluminum which seems like a better idea than steel as it's lighter so it won't affect stability and it won't corrode. You could use screws and PU sealant rather than welding. I guess it would be best to keep the aluminum skin isolated from the steel, even though in contact less noble dissimilar metals only suffer from galvanic corrosion when immersed in an electrolyte. 

[David Mack]

Others have used West epoxy and fibreglass. But if your wooden cabin top is in a condition where it needs sheathing, you are only delaying the inevitable.

[Tony Brooks]

It was not long ago we had a longish discussion on this topic so have a search.

 

FWIW we built a series of cruisers from hull and inner mouldings but made the cabin sides from thick plywood  while the roof was formed from truck cant rails on top of the cabin side, transverse aluminium top hat sections bent to the curve and skinned with more ply self tapped into the top hat section. The ply in those days was better quality than the so-called marine ply you can more easily buy today.

The countersunk screw holes and the joins in the ply sheets were filled with standard body filler but today they would have used epoxy filler. So we had a good one piece surface to work on. We then covered the roof with fibre glass roving sheets (not chopped strand mat) and built up many layers of epoxy two pot paint. This soaked the roving and stuck it to the wood and aluminium cant rails. Some 30 years later I met one on the GU and the owner told me he had no roof leaks. If the roof is tongue and groove I fear the movement may make this unsuitable.

[Bee]

If the actual roof is stll soundish  then  I would recommend decent gritty roofing felt, use the recomended black goo for the seams, its quite tough for a bit of walking on, fold it over the edges an inch or two and fix a wooden strip to cover the flappy bit.  Masonite is not bad stuff but the bottom edge is vulnerable to soaking up water, BEngo's brown gooey stuff is, i think Synthaprufe, with luck and some clever use of gooey stuff and tape along the bottom edge it will give good service for years

[BEngo]

BEngo's brown gooey stuff was not Synthaprufe- though it may have been pretty similar.  The stuff I used was an 'own brew' from one of the national builders  merchants.

 

This stuff looks pretty similar

https://bond-it.co.uk/bitubond-range/rubber-bitumen-emulsion/

 

N