Painting narrowboat roof - preparation

[Balloon]

My boat is going undercover in Feb for blacking and some other jobs. While I’m there I’m going to paint the roof myself. Currently it’s in a smooth but very slightly sanded surface with a sheen to it but not gloss. I’ve decided to use Jotun Conseal for the new deck paint. As the old surface has a sanded finish can I paint over it? Do I need to take it back to bare metal, back to the primer underneath, how far back does it need to go, basically, before I can paint over?

 

I’ve attached a picture of how it’s currently looking. As you’ll see, some of the paint has blistered off and what you’re seeing is the previous red top coat, not primer (the primer is blue, under the red)

 

any helpful comments will be gratefully appreciated. Thanks

[Tony Brooks]

I would suggest the previous preparation was not good enough, the roof was painted while damp, or a lot of stuff has been stored on it that held water against the paint. As you don't know which it would probably be a good idea to at least go back to the red so you can give it a good abrading and de-greasing. The sanded paint may give you problems, especially if the sanding is in the red paint.

[Balloon]

Thanks @Tony Brooks, nothing has been stored on it. I’d say the previous preparation not being good enough is the best option from those (it was the previous owner who painted it not me!). So if I take it back to the red that might be good enough? The red is smooth not sanded. I use a powered sander to take it back to the red? What disk given that the cream surface is sanded? And can I apply the Jotun straight to the red or does it need an undercoat. 
 

sorry for all the questions. It’s my first time doing this type of thing, although I’m generally fairly handy with stuff. 

[BEngo]

I would hire a scabbler, buy some tungsten carbide wheels for it and have all the roof paint off to bare metal. Then apply a full paint scheme from one maker.  An angle grinder and wire brush is useful for corners etc.

 

That way you know what has been done and are not relying on your new and expensive paint being held on by someons else's  paint job several layers down.

 

N

[Higgs]

It isn't clear, from the picture, to see the texture of the sanded areas. The disks of a sander, with even an 80 grit paper, will not last long, and will wear out quickly, prepping the sanded area. If the sanded area has been over-painted, to the point that the sand no longer gives grip, it would be better to take it off completely. For that, you will need a scabbler. The only other suggestion would be to wire-brush the surface to remove flaking paint, then apply another non-slip deck paint. I would suggest thoroughly washing the roof, but at this time of year, it wouldn't dry that quickly. 

 

 

Edited December 18, 2021 by Higgs

[matty40s]

If you dont have a heated dock, I would forget it until summer, it will not set, and will bloom overnight with condensation.

February is not a good month to paint without heat and humidifier assistance. Look at today's humidity.....doesnt drop below 97 all day

[A A Matthews]

I would be interested in feedback regarding the following; Dutch Cruiser , small area upper deck , circa 4x 4 m probably, containing fixed chair and wheel. Historical’ vinyl’ or similar floor tile and painted curling / cracking and looking absolutely rubbish . My treatment  proposal is to scrape / lift etc all tiles, clean / prepare steel substrate with intention of painting with anti slip marine grade paint.  So what paint/ paint systems do you fellow boaters recommend or not recommend and any advice all greatly received , thanks A A

 

[LadyG]

19 minutes ago, A A Matthews said:

I would be interested in feedback regarding the following; Dutch Cruiser , small area upper deck , circa 4x 4 m probably, containing fixed chair and wheel. Historical’ vinyl’ or similar floor tile and painted curling / cracking and looking absolutely rubbish . My treatment  proposal is to scrape / lift etc all tiles, clean / prepare steel substrate with intention of painting with anti slip marine grade paint.  So what paint/ paint systems do you fellow boaters recommend or not recommend and any advice all greatly received , thanks A A

 

I believe that if you want to get back to bare steel a scabbler can be hired, try a search for that to bring you to other threads.

If it has much rust then be prepared to get rid, maybe an angle grinder with various types of discs, then Vactan or Fertan are usually recommended 

Then the usual primer(s), undercoats, topcoats. 

You can get technical advice from SML paints.

I buy the granules to add to the paint, but I'm talking light use.

 

[Mike Hurley]

3 minutes ago, LadyG said:

I believe that if you want to get back to bare steel a scabbler can be hired, try a search for that to bring you to other threads.

If it has much rust then be prepared to get rid, maybe an angle grinder with various types of discs, then Vactan or Fertan are usually recommended 

Then the usual primer(s), undercoats, topcoats. 

You can get technical advice from SML paints.

I buy the granules to add to the paint, but I'm talking light use.

 

So here you are giving paint advice yet in in another thread you are asking paint advice, bored tonight or is the wine all gone?

[LadyG]

3 minutes ago, Mike Hurley said:

So here you are giving paint advice yet in in another thread you are asking paint advice, bored tonight or is the wine all gone?

I always recommend that people get technical advice from the paint supplier. I just say what has worked for me , or how I approach things.

I have never used either a paint scabbler or an angle grinder.

I have never used floor paint.

I asked for advice in the faint hope that someone has tried the granules instead of the high build primer as I have one, but not the other 

Edited June 25, 2023 by LadyG

[rusty69]

3 minutes ago, Mike Hurley said:

So here you are giving paint advice yet in in another thread you are asking paint advice, bored tonight or is the wine all gone?

Woa! Bit harsh innit. 

[Mike Hurley]

4 minutes ago, rusty69 said:

Woa! Bit harsh innit. 

Well maybe but she is always  quoting about SML paints and how to do it then asking how to do stuff, seems odd to me. No offence intended but asking advice about painting boats while giving advice about painting boats seems strange, i know what i know and if not i dont offer advice.

[rusty69]

Just now, Mike Hurley said:

Well maybe but she is always  quoting about SML paints and how to do it then asking how to do stuff, seems odd to me. No offence intended but asking advice about painting boats while giving advice about painting boats seems strange, i know what i know and if not i dont offer advice.

I often give advice about electrical stuff whilst asking at the same time. 

 

Whilst I know certain aspects, I am far from 100% knowledgeable. 

 

I would also recommend SML paints technical advice, having spoken to Kevin at SML three times this last week. 

[Mike Hurley]

I followed your post on blacking, good stuff. A 70 footer is no mean feat.

[rusty69]

Just now, Mike Hurley said:

I followed your post on blacking, good stuff. A 70 footer is no mean feat.

It's 70 mean feet. Not sure how many mean metres that is. 

[LadyG]

5 minutes ago, Mike Hurley said:

Well maybe but she is always  quoting about SML paints and how to do it then asking how to do stuff, seems odd to me. No offence intended but asking advice about painting boats while giving advice about painting boats seems strange, i know what i know and if not i dont offer advice.

No point in asking a paint supplier about an off the wall scheme. It's only a small area, and as explained I don't  have the right coating.

[Mike Hurley]

Painting is 95% preparation and 5% application.

[rusty69]

Preparation is 95% perspiration and 5% abrasion. 

[Mike Hurley]

Back in the 70s i used to paint arctic trailers with the Cadbury chocolate stickers and the Typhoo Gnu, remember them?

Took 3 days to rub the trailers down and 1 day to paint then another day to apply the stickers, i hate painting trucks. Custom paint jobs on motorcycles was more my thing.

[A A Matthews]

Well what a response and thanks to all.

Not all were helpful however with some comments that appeared to be rather personal and not really about the subject at hand. Essentially I was just interested in either positive or negative feedback on types as in 2 pack epoxy / acrylic / add your own abrasive /  ready mixed abrasive/ to primer or not to primer / recommended 2 pack epoxy filler to deal with pitting etc.

And yes as a long term professional electrician and antique furniture restorer - conservator I know much about preparation and of patience 

 

[rusty69]

Well, I am sorry my comment angered you. Good luck with your painting. 

[MtB]

17 minutes ago, A A Matthews said:

And yes as a long term professional electrician and antique furniture restorer - conservator I know much about preparation and of patience 

 

Your question strikes me as very specific. Might be better to start a thread of your own.

 

 

[LadyG]

16 minutes ago, A A Matthews said:

Well what a response and thanks to all.

Not all were helpful however with some comments that appeared to be rather personal and not really about the subject at hand. Essentially I was just interested in either positive or negative feedback on types as in 2 pack epoxy / acrylic / add your own abrasive /  ready mixed abrasive/ to primer or not to primer / recommended 2 pack epoxy filler to deal with pitting etc.

And yes as a long term professional electrician and antique furniture restorer - conservator I know much about preparation and of patience 

 

Aha, now I don't think you mentioned these ideas,  I'm sure you will get responses.

I've said all I'm going to say, but I'm sure you are aware that there are people who post on forums and there are people who know an awful lot about preparation and coatings, some are highly technical and some are very practical.

[Bee]

I am highly experienced in not doing a very good job of the prep and thinking that new paint will stick to a bad surface. 

[LadyG]

On 26/06/2023 at 09:29, Bee said:

I am highly experienced in not doing a very good job of the prep and thinking that new paint will stick to a bad surface. 

After painting my roof this spring, I was really pleased, it's the same paint as last year, grey white, to keep cabin cool. Prepped it nicely, but decided to use a brush, instead of a roller. Bad idea, grooves collect dirt.

Moored my beautiful roof under a beautiful tree for a week. It is no longer clean and white, it is covered with sticky stuff off the beautiful tree,  sooty black stuff, with sporadic bird droppings. Spent two hours with sugar soap, hot water, deck brush, scrubbing brush and sandpaper to get it back to acceptable. Another five sessions will do the job. Something to look forward to?

Not.