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spray foam insulation how well does it stick


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Just posting as some may be interested in a little real world experience.

 

We had the boat sprayfoamed before fitting out about 10 years ago. I recently came across a small piece of sprayfoamed steel that we cut out of the cabin roof after the sprayfoaming. It has been outdoors in my garden ever since. The steel was preprimed before delivery to the builder and another coat of primer added by him. On the inside the next layer was the foam which unfortunately does not appear to be quite as thick as requested (about 30mm instead of 40) BUT is still sticking to the primed steel apparently perfectly. On the other side the builder had added 2 coats of expoxy primer and one 2 pack gloss (Jotun) It has survived tolerably well but rust is clearly staring to creep underneath the paint.

 

On another part of the boat I had a hatch made up from bright steel, it looked nice so it was given 2 coats of varnish (sold as suitable for steel) and looked shiny for a while but after a couple of years brown (rust) could clearly be seen creaping under the varnish even though most of the varnish was intact. If it had been paint and not varnish you would never have known.

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The sprayfoam is pretty good, it makes you wonder if you could sprayfoam the steel under the floor (I won't be trying it though)  The top surface is not bad either, the rust seems to have started from the edges where I don't suppose there was any paint in the first place. I don't think cheap & cheerful gloss paint would have lasted so well.

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12 minutes ago, Bee said:

The sprayfoam is pretty good, it makes you wonder if you could sprayfoam the steel under the floor (I won't be trying it though)  The top surface is not bad either, the rust seems to have started from the edges where I don't suppose there was any paint in the first place. I don't think cheap & cheerful gloss paint would have lasted so well.

You are right I don't think I could have expected better particularly as the outer surface had some exposure to damp before painting, the actual boat has had a couple more coats on the outside since and is fine on the sides but one or two rust spots on the top which clearly got and gets more weather. I think the cost of the spray foam was probably much less than if I had painted the insides  and used a board type insulation. I wonder how well sprayfoam would work on untreated steel?

I wouldn't spray under the floor, difficult to keep clean and in winter when I am not on the boat the outside water keeps the boat warmer.

I didn't spray the engine room that might have been worth doing?

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I sprayed our boat myself and I reckon it will stick to untreated steel perfectly well. It sticks to hair, shoes, moustaches and dogs equally well. I used it as 'Bee' is all curves so boards would be difficult but even on a narrowboat I would prefer sprayfoam, those tricky upside down bits under gunwhales and an arched roof might get voids. If I ever did another boat I would pay someone else to do it though, the stuff is a nightmare to spray. 

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4 minutes ago, Bee said:

I sprayed our boat myself and I reckon it will stick to untreated steel perfectly well. It sticks to hair, shoes, moustaches and dogs equally well. I used it as 'Bee' is all curves so boards would be difficult but even on a narrowboat I would prefer sprayfoam, those tricky upside down bits under gunwhales and an arched roof might get voids. If I ever did another boat I would pay someone else to do it though, the stuff is a nightmare to spray. 

The only problem would be the millscale coming off but since it is sealed in by the sprayfoam why would it? I am very happy that I paid someone and it wasnt that dear certainly less than paying a painter or even buying the paint!

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1 hour ago, Bee said:

The sprayfoam is pretty good, it makes you wonder if you could sprayfoam the steel under the floor

Been there, done that. Sprayfoamed all of it.  (Professional job, not personally.)

Edited by system 4-50
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Just now, nb Innisfree said:

My experience :

When I was fitting out Innisfree a fellow diy fitter cut out his window ports from spray foamed 4mm steel cabin sides, a couple of cutouts were bare steel the rest were primed, the foam from bare ones came away easily the primed ones were difficult to remove. 

 

Edited by nb Innisfree
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