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Mad Harold

How do I sprayfoam a ceiling?

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Because of condensation under the foredeck of my fibreglass cruiser,(it's not insulated ) I decided to sprayfoam it.

Seen videos of it being done on the web,and they seem to use some stuff that squirts on with the consistency of milk,and then immediately expands and sticks.

The stuff I am using comes out thick and gikky but immediately falls off. The foam I am using is Soudal but I am sure this is the wrong stuff for the job.

Could anyone tell me the make of foam suitable for ceilings?or is there a technique for getting this stuff to stick? For example,using a greased piece of ply as a temporary former?

Any advice/suggestions gratefully received.

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Sounds like you are using standard builders foam rather than sprayfoam, this is understandable as proper sprayfoam only comes in big expensive "cans".

 

I have used builders foam to seal the underside of floorboards in an old house and want to do under the gunnels in the boat soon.

 

Plywood and grease sounds messy. Cardboard should be fine if you do a bit at a time, and covering it in clingfilm is less mess than grease (and it works). You will need to devise a way to support the cardboard and learn just how much foam to squirt in to fill the gap without too much dripping out of the sides. You can also put a few holes in the card to do a bigger area in one go.

 

Wear overalls , hat and gloves and use a suitable dust sheet to catch any droppings.

 

let us know how you get on, and ideally use the more expensive fire-rater foam.

 

...........Dave

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4 minutes ago, dmr said:

ideally use the more expensive fire-rater foam.

If its on a GRP boat I don't think the use of a fire resistant / retardant foam will make a ha'porth of difference to the survivability in a fire.

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4 minutes ago, Alan de Enfield said:

If its on a GRP boat I don't think the use of a fire resistant / retardant foam will make a ha'porth of difference to the survivability in a fire.

The same is probably true on a narrowboat, but its the sort of thing somebody might ask if the boat is up for sale. There are a lot of rules, regulations and best practices (see the thread on choc blocks) that probably are not important but some people worry more and more about this sort of thing.

 

............Dave (who currently has a towel wrapped round the stove flue, and has just sucked 3 litres of diesel out of the fuel tank into plastic coke bottles)

 

 

 

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17 minutes ago, dmr said:

The same is probably true on a narrowboat, but its the sort of thing somebody might ask if the boat is up for sale. There are a lot of rules, regulations and best practices (see the thread on choc blocks) that probably are not important but some people worry more and more about this sort of thing.

 

............Dave (who currently has a towel wrapped round the stove flue, and has just sucked 3 litres of diesel out of the fuel tank into plastic coke bottles)

 

 

 

Many, many years ago I was on my way to night school when I saw a Reliant 3-wheel van in front of me start to 'smoke', he pulled over to the kerb and got out, by the time I had overtaken him (>1 minute ?) it had burst into flames and was burnt out - pretty much just the engine and wheels left.

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You find misting the area first will help the foam expand and cure faster. Be careful, though; you want to dampen the area, not wet it. The can also needs to be warm (15 to 20 degrees). if cold the foam will expand very little and not cure properly.

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7 hours ago, Alan de Enfield said:

Many, many years ago I was on my way to night school when I saw a Reliant 3-wheel van in front of me start to 'smoke', he pulled over to the kerb and got out, by the time I had overtaken him (>1 minute ?) it had burst into flames and was burnt out - pretty much just the engine and wheels left.

A friend had a dispute with a neighbour who accused him (incorrectly) of putting stuff into the skip the neighbour had in the road outside his house. On his way home from the pub my friend (and a couple of his mates) picked up the neighbours Reliant Robin and carefully placed it in the skip.

 

...................Dave

 

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Easier and probably  cheaper to use sheet kingspan insulation, glued up with foam,  and then fill in any edge and joint gaps with foam and tape over with the foil tape.

One thing that catches folk out is that the foam cans only work properly when the outlet is at the bottom.  If you use a gun type holder then this is automatic, but overhead work needs a flexy extension to get the foam to stick.  If you use the cans with a built in nozzle you need to extend that so you can keep the can upside down.

N

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100% agree wih the Celotex/Kingspan insulation or if you need something more flexible look at a product called Drytherm. I would also point to other products for example multi layered foil. There is also a great advantage to preventing air movement by incorporating a vapor barrier.

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4 hours ago, BEngo said:

Easier and probably  cheaper to use sheet kingspan insulation, glued up with foam,  and then fill in any edge and joint gaps with foam and tape over with the foil tape.

One thing that catches folk out is that the foam cans only work properly when the outlet is at the bottom.  If you use a gun type holder then this is automatic, but overhead work needs a flexy extension to get the foam to stick.  If you use the cans with a built in nozzle you need to extend that so you can keep the can upside down.

N

 

My neighbour has insulated his whole boat using kingspan (or cellotex) and stuck the sheets on using sprayfoam from cans. The sprayfoam acts as an adhesive and also fills any gaps but you do need to use supports or props to keep the kingspan in place until the sprayfoam has cured.

 

He's done the underside of the roof this way and it seems to work very well. He cut half inch slits in the one inch thick kingspan in order to get it to conform to the curve of the roof. I was concerned that this would reduce the insulation properties of the kingspan, but he said the cuts would fill with the expanding sprayfoam. Anyway, it's all stuck on very well so that's what I'd do.

Edited by blackrose

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34 minutes ago, blackrose said:

 

He's done the underside of the roof this way and it seems to work very well. He cut half inch slits in the one inch thick kingspan in order to get it to conform to the curve of the roof. I was concerned that this would reduce the insulation properties of the kingspan, but he said the cuts would fill with the expanding sprayfoam. 

Which side of the kingspan did he cut the slits?

I would put the cuts on the inside face, using a circular saw to make cuts 2-3 mm wide, spaced so that they close up completely (on the surface) when the board is curved. That way you know you don't have any unknown splits or voids in the foam, and you can then use the foil jointing tape over the cuts to ensure a complete continuous vapour barrier.

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37 minutes ago, David Mack said:

Which side of the kingspan did he cut the slits?

I would put the cuts on the inside face, using a circular saw to make cuts 2-3 mm wide, spaced so that they close up completely (on the surface) when the board is curved. That way you know you don't have any unknown splits or voids in the foam, and you can then use the foil jointing tape over the cuts to ensure a complete continuous vapour barrier.

 

He cut them on the side facing the ceiling/roof using a Stanley knife set to a fixed depth and a straight edge. With your method you'd need to cut Vs and do a trial to see exactly how much they closed up to ensure they close fully. If they don't you're reducing the insulation properties of the kingspan dramatically and I'm afraid aluminium tape is only a vapour barrier not an insulation material. 

 

With his method you only need to cut single scores which will open up and as long as you use enough sprayfoam they should fill up so that the insulation properties of the kingspan isn't reduced. That's the theory anyway and it seems to make sense to me.

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1 minute ago, blackrose said:

With your method you'd need to cut Vs and do a trial to see exactly how much they closed up to ensure they close fully.

Yes, you’d need to do a test but no, you wouldn’t need to cut a vee. The 3mm kerf of the saw would close up as the panel curved, leaving no gaps. Unlike his method where the cuts open up as it’s curved, leaving many gaps. 

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29 minutes ago, jddevel said:

I`ll repeat look into DryTherm

I think it's basically rockwool which is ok as long as a vapour barrier is used in conjunction. However in terms of insulation performance it's not as good as kingspan, cellotex or properly applied sprayfoam.

Just now, WotEver said:

Yes, you’d need to do a test but no, you wouldn’t need to cut a vee. The 3mm kerf of the saw would close up as the panel curved, leaving no gaps. Unlike his method where the cuts open up as it’s curved, leaving many gaps. 

Yes I see. However, if the cut is not a V profile then when it closes up the outer edges of the cut will be in contact before the inside potentially leaving long open holes inside across the width of the kingspan. Personally I'd rather fill any holes with sprayfoam while I'm sticking the stuff up onto the ceiling.

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My experience with sprayfoam from a can suggests that it will fight you strongly to avoid filling in the V fully.  I would cut the inside side.

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3 minutes ago, system 4-50 said:

My experience with sprayfoam from a can suggests that it will fight you strongly to avoid filling in the V fully. 

 

I don't really get that? Fight you? 

 

My experience with sprayfoam from a can is that it will expand and go everywhere the sun don't shine!  Anyway, it's not my boat so whoever's doing it can decide for themselves how to do it best.

Edited by blackrose

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23 hours ago, dmr said:

Sounds like you are using standard builders foam rather than sprayfoam, this is understandable as proper sprayfoam only comes in big expensive "cans".

 

I have used builders foam to seal the underside of floorboards in an old house and want to do under the gunnels in the boat soon.

 

Plywood and grease sounds messy. Cardboard should be fine if you do a bit at a time, and covering it in clingfilm is less mess than grease (and it works). You will need to devise a way to support the cardboard and learn just how much foam to squirt in to fill the gap without too much dripping out of the sides. You can also put a few holes in the card to do a bigger area in one go.

 

Wear overalls , hat and gloves and use a suitable dust sheet to catch any droppings.

 

let us know how you get on, and ideally use the more expensive fire-rater foam.

 

...........Dave

Thanks Dave,here's how I got on.

A cardboard template was too floppy so I tried a piece of ply.The clingfilm wouldn't cling to it so I used a piece of perspex left over from when  I replaced my windows.Unfortunately the foam stuck to the clingfilm better than the underside of the deck.The foam stuck everywhere except where I wanted it,the underside of the deck.The dustsheet,my overalls,and in what's left of my hair!

The problems were working on my back in a confined space and trying to get a suitable gap to get the nozzle into.

After about two hours I realised that this was not going to work,yes some foam had stuck but mostly it hadn't and there were bald patches all over,so discretion being the better part of valour,I threw the sponge in.It then took another two hours to clean up.

I think if I attempt this job again I may take Bengo's suggestion and use Kingspan  or perhaps polystyrene sheet cut to managable lengths and glue them in place.

As I feel devoutly pissed off with todays work,I am going to have a shower and go to the pub and give this job a good dose of thinking about.

Hope your job goes better than mine.

  • Happy 1

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5 minutes ago, Mad Harold said:

Thanks Dave,here's how I got on.

A cardboard template was too floppy so I tried a piece of ply.The clingfilm wouldn't cling to it so I used a piece of perspex left over from when  I replaced my windows.Unfortunately the foam stuck to the clingfilm better than the underside of the deck.The foam stuck everywhere except where I wanted it,the underside of the deck.The dustsheet,my overalls,and in what's left of my hair!

The problems were working on my back in a confined space and trying to get a suitable gap to get the nozzle into.

After about two hours I realised that this was not going to work,yes some foam had stuck but mostly it hadn't and there were bald patches all over,so discretion being the better part of valour,I threw the sponge in.It then took another two hours to clean up.

I think if I attempt this job again I may take Bengo's suggestion and use Kingspan  or perhaps polystyrene sheet cut to managable lengths and glue them in place.

As I feel devoutly pissed off with todays work,I am going to have a shower and go to the pub and give this job a good dose of thinking about.

Hope your job goes better than mine.

Thats sounds horrid, so the pub is a good idea.

It did work for me in a house but I now suspect brick and timber joists are probably a much better target for the foam than GRP. I folded the edges of the card to stiffen it but was only applying the foam to a narrow area. I assume the GRP surface is quite rough, or is it a gel coat?

We have polystyrene insulation, its adequate but not ideal, so Kingspan or equivalent is probably better.

 

How about gluing some wooden battens onto the "ceiling" with a "no more nails" type glue then fixing a thin plywood ceiling (deckhead to that and then squirting the foam in via the edges and a few suitable holes????    or just stuffing in a load of rockwool or similar?

 

................Dave

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2 hours ago, blackrose said:

I think it's basically rockwool which is ok as long as a vapour barrier is used in conjunction. However in terms of insulation performance it's not as good as kingspan, cellotex or properly applied sprayfoam.

Depends on the thichness and I believe more environmently friendly. It`s a matter of choice. As I stated earlier a vapour barrier is important and should be considered as air movement is a contributor to condensation.

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41 minutes ago, tree monkey said:

How about tipping the boat upside down,  stop all the messy dripy stuff

:)

Finally a sensible suggestion...

  • Greenie 2

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4 hours ago, WotEver said:

Yes, you’d need to do a test but no, you wouldn’t need to cut a vee. The 3mm kerf of the saw would close up as the panel curved, leaving no gaps. Unlike his method where the cuts open up as it’s curved, leaving many gaps. 

Exactly. With half depth saw cuts you would know you had full insulation over the upper outer half of the board thickness, although there would be long triangular voids on the inner half. But better there than on the outer half as in Blackrose's method, where I doubt the glue would fill them, and they would be directly against the cold surface of the cabin shell.

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16 hours ago, jddevel said:

Depends on the thichness and I believe more environmently friendly.

 

No not really, Insulation materials are compared on the basis of a given thickness otherwise you're not comparing like for like. As for more "environmentally friendly" that's a rather vague term. In terms of the manufacture of the material Drytherm/rockwool may have reduced environmental impacts compared to kingspan or cellotex, but if (as seems likely) that over the lifetime of the material the energy used to heat the boat is much greater when rockwool is used, then those initial environmental gains will be wiped out and the kingspan/cellotex will be more "environmentally friendly" overall.

Edited by blackrose

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15 hours ago, David Mack said:

Exactly. With half depth saw cuts you would know you had full insulation over the upper outer half of the board thickness, although there would be long triangular voids on the inner half. But better there than on the outer half as in Blackrose's method, where I doubt the glue would fill them, and they would be directly against the cold surface of the cabin shell.

 

I disagree. You don't want any voids in the kingspan at all. If you end up with voids on the bottom half you've reduced the insulation properties drastically. I think you've misunderstood the method I described. I never suggested using glue, I was talking about using expanding foam which fills the voids. You might reply that I don't know that the foam has filled the voids on the side of the kingspan against the steel, but to me it has to go somewhere when the kingspan is propped against the ceiling. One obviously can't check behind the kingspan once it's stuck up there but looking at my neighbour's work the sprayfoam was emerging around all sides of the kingspan so I see no reason why it wouldn't expand into open voids.  Also with your method you don't actually know whether there are voids in the kingspan on the side that's stuck to the steel because depending on the curve of the roof that side may split unless you score it before bending it. With your method you're making cuts on the side that's going into compression which is a classic case of misunderstanding the problem because you've done nothing about the side that's going into tension. (Look at diagram E below). If the kingspan splits it will split on the side that goes into tension and cutting the bottom side to facilitate easier bottom side compression doesn't solve the issue of top side tension. You could always do a dry run before sticking it up - offer it up, bend it into position, take it down and check for any splits. But if you find splits in the top side of the kingspan then what are you going to do?

 

Figure 1-14. The five stresses that may act on an aircraft and its parts.

Edited by blackrose

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