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How long should roof paint last?


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A bout 2 1/2 years ago I had Theodora's roof painted.  Scabbled down to the bare metal and a lovely finish.  The man said that it should last about ten years.  I was disappointed to see cracks and rust as shown in the photos.  What could have caused this, do you think?

 

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7 minutes ago, mark99 said:

Theo did you lay your ropes there? Or anything?

 

 

No.  ropes are further aft.

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Look very much like scratches, can you think how you might have done these?  Other possibility is that they were done during painting and some damp got in then they were just painted over without fullre-preparation, but my guess is that you have done somehow done them.

 

That looks like a matt or raddle type finish so its relatively easy to do a local repair, a raddle type roof looks ok with a bit of "texture" so no need for a perfect repair. If its Craftmaster raddle then its worth putting a new coat on every four or five years.

 

.........Dave

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1 hour ago, Theo said:

A bout 2 1/2 years ago I had Theodora's roof painted.  Scabbled down to the bare metal and a lovely finish.  The man said that it should last about ten years.  I was disappointed to see cracks and rust as shown in the photos.  What could have caused this, do you think?

 

1273785776_2019-04-0815_20_15.jpg.ac6c0b1d5084fa62ccda23fc9c298e51.jpg1526265209_2019-04-0815_20_33.jpg.d4d6a7f1b193dd00b8022823c1b85071.jpg196469651_2019-04-0815_20_47.jpg.54fa897d1a1f2f9c502f87bf55c2c5ec.jpg

 

Is it International Rochelle Red?

 

If so it seems to go like this after 5-7 years if it is in a position where it gets a lot of UV light.

 

My boat has Rochelle Red on the handrails, odd bits of roof detailing, front deck and coachlines. The handrails andcroof detailing were repainted after 7 years (but could have been done earlier. The decks a year later and this yesr the coachlines are showing signs pf the cracks appearing.

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Yes, it looks like it is due to scratches. If the paint is scratched then rust will form at the exposed metal and then undercut the paint and lift it. Even if the scratch doesnt go down to the steel, it will still rust through the primer etc.

2 1/2 years though, it doesnt look good. You would really need to examine the coating with a pen knife to check adhesion and brittleness to see try and see if it was a surface preparation or paint application isssue.....or if it was just damage post painting. Was that part of the roof covered with anything during the winter? Did you put any coal or wood on the roof, that may have caused scratching and then been a focus for condensation on and standing water. Roof paints are pretty poor at resisting pooling water if you put stuff on it. The way the coating is lifting where the rust has penetrated says to me that the coating looks brittle.

If all of the above can be ruled out, and the coating 'pings' off easily with a pen knife revealing bright steel, then you may consider problems during application, but then you need to furnish us with all the detail, type and number of coats, dates it was done, weather when it was done, how was it applied, thickness applied, type of paint, temperature etc etc etc.

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To answer the question in the OP, our roof paint (which is a combination of smooth and non-slip) is now 8 years old. Until recently it remained perfect. Last year I noticed that a small area (junction of smooth and non-slip) was lifting with corrosion underneath. But it had lasted at least 7 years, and the remainder is not showing any signs of distress after 8.

 

i would expect that the problem relates to preparation - a tiny bit of rust left, which harbours damp and causes corrosion to spread under the new paint. Even though the damage looks like scratches, I wonder if it isn’t just old scratches (containing corrosion) coming through again despite the repaint.

 

I’d be pretty fed up if a repaint went like that in 2.5 years.

Edited by nicknorman
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I think it may be thin paint, tiny scratches should not really penetrate through the paint but it looks to me as though that is the problem. Also on the top picture there is a bubbly bit that looks as though water has just soaked through the paint. Roof paint has a hard life and one (or two?) top coats are still only a few microns thick, if it was applied on a hot day the stuff needs thinning to get it to cover smoothly, I would patch it, sand it nice and flat and then overpaint the lot with a couple of coats of new paint. I have had (so far) good results with the deck paint from TA industrial paints Wolverhampton (They might be black country paints now) - no connection. 

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The sun plays a part too!

Yesterday for example my roof got very hot. expansion and contraction due to heat and cold will crack paint. after a time.

I painted my roof with International walkway paint two years ago, and some rusty cracks are showing especially between the hatch rails.+

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