Damp motorhome project - Roof repair

[Jamesh]

Don't use fiberglass resin it's a poor glue. It will melt polystyrene too.

I'd use a polymer based sealant like ebt silkaflex or m3 m5100 tbh.

Something like this....

https://rover.ebay.com/rover/1/710-...0001&campid=5338547443&icep_item=273521763819

Cheers James

 

[Argar]

The first beam bonded in lots more to go!

 

[Clankie]

I have read the above thread with interest and now have some doubts about the way to proceed....
I’m back to the aluminium roof skin, now waterproof with new timber roof battens in place. My question is what order to rebuild the ceiling. Originally Benimar had 3mm ply inside the alloy stapled to the top of the battens then 25mm insulation then head lining. That is construction process as the last bit to go on is the alloy roof skin. Now I’m rebuilding from the inside!!
I must stop moist air getting in contact with the cold aluminium that I know. I was going to glue 3mm hardwood ply to the underside of the alloy between the battens as before then 25mm Celotex then headlining. I was doing it this as it was the original construction plan, however I an now thinking perhaps I should go for insulation onto the alloy skin then tape the gaps from the sides of the battens to stop any moist vapour getting in contact with the alloy then the ply and headlining.
Thoughts please as I am keen to proceed. At this time of year given the humidity and cold I am struggling with condensation on the inside of the roof!!

 

[68c]

I had to do a similar repair. With all the roof ply and insulation removed, looking up there were so many pinprick corrosion holes it looked like the night sky. I chemically treated the corrosion then applied self adhesive alloy patches, marked the inside then sealed the outside first. That meant I could then know where to apply the interior patches. I then painted the inner surface of the alloy roof skin with household gloss. I did glue a 3mm ply sheet up first then the ew roof battens, celotex and patterned wallboard. I worked on the principle that the 3mm ply, roof battens and wallboard formed a box section for strength. Once all was up I sealed all edges with Silastik to prevent moisture rising up to the alloy skin. I applied two coats of EDPM rubber to the roof to finally seal everthing. EDPM rubber was Pro Guard Liquid Rubber from Allrimes Coatings Ltd.

 

[Clankie]

Thanks 68c for you assistance, I did think the ply onto the alloy would give it more strength, my original thoughts. My new battens are already in next to the alloy I was worried the whole structure would collapse however I have run sikaflex above the battens to the alloy and that is firm now. I will cut the ply to fit in between the battens, glue it to the alloy and run a bead of sealant from ply to batten as well, it will also stop moist air getting to the alloy As well. Then insulstion then headlining. As I said I must get something onto the alloy as it is dripping in these conditions. What a time to do a rebuild like this!! Thanks for doing a sketch as well, a drawing is better than words.

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[Clankie]

Oh I meant to ask where did you purchase the head lining, wall board? I have vinyl 6mm foam backed for the bathroom from HMS Supplies in Dorset, very good quality.

 

[68c]

Can't remember now. Just did a quick Google search under 'caravan wallboard', plenty of results.

morlandsuk.com
olearysmotorhomes.co.uk
thecaravanwharehouse.co.uk

It may have been Olearys as I have bought other things from them.

You could try sending a sample of the old board to try to get a match, although I took the opportunity to get away from the outdated cream wallboard we had. Went for a textured white, looked great. I used it on the sides and the ceiling, also clad the bathroom in it. As long as the edges are sealed it will be shower proof.

Keep an eye on the delivery price when ordering, perhaps one of them is close enough for you to collect. It is flimsy stuff being only 3mm thick so if only collecting a few sheets may be worth taking a thicker sheet of ply or chipboard to carry it if on a roof rack. Most sheets are 7ft x 4ft. Also suggest order more than you need in case of problems, annoying to wait for a second delivery.

 

[Clankie]

Thank you, I’ve just returned from the MH, put up 2 pieces of ply. Test run, I’ll get quicker now I have a system. It’s nice to speak with someone who has had the same problem. You made me laugh with the stars at night, my son‘s van was the same. The first weekend they went away the kids were collecting rain water in pans, they thought it was great fun. My van has a 10 year warranty on the body, it five years old now, just had a hab check to maintain the warranty. It’s the only thing now that’s covered. My son‘s Benimar 6000 ST 1999 plate
is mechanically ok but the roof was like yours if not worse. Still it keeps me busy in Covid times, we should have been in Spain!!! Rats
I will look for wall board next...Thank you

 

[Argar]

More wood sealed and now screwed in - will use PU glue to join as well when I come to do the ceiling board in the bathroom.

Question on the for the wallboard adhesive, can this fill small differences between the levels of the beams (up to 2 mm). Unfortunately a few of the beams are slightly smaller! Too cold now to do any wallboards - so will have to wait for it to get warmer!

 

[Terry]

I can see a lot of wooden framework but cannot work out where for

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[Terry]

To answer your question ,Yes if you use a gun application glue I use Puraflex 40

 

[Argar]

Thanks Terry.

I've chosen the 2 part wallboard adhesive (e.g. https://magnummotorhomes.co.uk/shop...pair-your-van/magnum-m400-wallboard-adhesive/).

Already bought the adhesive - so wondering whether this will work if there are voids with some beams?

 

[Terry]

Hi never used or seen it....if it's like a putty mix then don't squash it as much ..... personally I would use the Puraflex or Siromer grip and grab adhesive

 

[Argar]

Oh I meant to ask where did you purchase the head lining, wall board? I have vinyl 6mm foam backed for the bathroom from HMS Supplies in Dorset, very good quality.

We bought our Wall/Ceiling board from Magnum Motorhomes (https://magnummotorhomes.co.uk/) - if you contact them they'll send samples so you can look for something that'll work.

They also sell Wallboard adhesive which was suggested to me to bond the structure/insulation.

 

[Argar]

Built out the structure for the root in the rear of the motorhome now - all structure in apart from skylight frames!

Next step is cutting insulation and bonding in new plywood and ceiling boards. Happy with progress so far, now need some warmer weather for the glue!

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[Johnenigma]

Figaro Tanalised timber does look the way to go - not as expensive as hardwood!

After talking to a roofer about tanalised wood, I found out that it contains copper. I then Googled tanalised wood and aluminium. Do not place tanalized wood against bare aluminium, it will corrode the aluminium. I have just started trying to repair my rotten motorhome, which is why I am reading this post. Very helpful and informative.

 

[Ian Bosman]

After talking to a roofer about tanalised wood, I found out that it contains copper. I then Googled tanalised wood and aluminium. Do not place tanalized wood against bare aluminium, it will corrode the aluminium. I have just started trying to repair my rotten motorhome, which is why I am reading this post. Very helpful and informative.

Aluminium will corrode against other metals due to electrolytic reaction, just turns to powder eventually. So must be the copper in the canalised wood.

 

[Ian Bosman]

Aluminium will corrode against other metals due to electrolytic reaction, just turns to powder eventually. So must be the copper in the canalised wood.

Further thoughts, I know that word is a good material if it is kept dry but do wonder why we tend to go for wood when aluminium is better for strength and lightness but it is not so easily sourced and requires a bit of know how for assembling, welding is not for the faint hearted. One reason motorhome/caravan manufacturers use ally is the longevity of it.

 

[Terry]

Tanalised wood will need drying out(a lot) it's put in a pressure chamber to force mixture all throughout the wood. Usually sopping wet when you buy it.I would think a lick of oil based paint would stop any reaction and it would take years before any takes place

 

[Argar]

After talking to a roofer about tanalised wood, I found out that it contains copper. I then Googled tanalised wood and aluminium. Do not place tanalized wood against bare aluminium, it will corrode the aluminium. I have just started trying to repair my rotten motorhome, which is why I am reading this post. Very helpful and informative.

Hi,

With the bonding adhesive between the wood and aluminium, I suspect you'd be OK. The van I'm working on is a GRP exterior so not an issue!

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[Argar]

Further thoughts, I know that word is a good material if it is kept dry but do wonder why we tend to go for wood when aluminium is better for strength and lightness but it is not so easily sourced and requires a bit of know how for assembling, welding is not for the faint hearted. One reason motorhome/caravan manufacturers use ally is the longevity of it.

I considered doing this but changing the material scared me too much!

 

[Argar]

With the weather starting to warm up (although doesn't feel like it today!) looking at getting restarted on my damp repair project. Was wondering what tool people would recommend for cutting the old wallboards to give a straight edge ready for the new board?

DJL220 and The_Kraken I think I saw cuts similar to what I need to do on your threads but couldn't see what tool you used?

 

[DJL220]

With the weather starting to warm up (although doesn't feel like it today!) looking at getting restarted on my damp repair project. Was wondering what tool people would recommend for cutting the old wallboards to give a straight edge ready for the new board?

DJL220 and The_Kraken I think I saw cuts similar to what I need to do on your threads but couldn't see what tool you used?

I freehanded it with a multi tool after drawing a line on the board. It really depends on where you are cutting, you could rig up a straight edge and then use a multi tool or a light weight circular saw and use the depth stop on the blade. I went for the multi tool so I could feel my way through the wall board. A dremel with a saw blade could also be used.
You could if you are able to rest the new wallboard next the replacement and use the edge of the new board as a guide ?
hope that helps?

 

[Argar]

I freehanded it with a multi tool after drawing a line on the board. It really depends on where you are cutting, you could rig up a straight edge and then use a multi tool or a light weight circular saw and use the depth stop on the blade. I went for the multi tool so I could feel my way through the wall board. A dremel with a saw blade could also be used.
hope that helps?

Thanks DJL220 that confirms what I was thinking!

 

[Terry]

Tool wise I use various saws for cutting etc.Fav Wise i have a small plunge saw with a 4inch blade a larger one (track saw) also for cutting sheet stuff. Multi tool/ buzz saw but use it very carefully, and sharpen a used saw blade (like a chisel) for seperating stuff. The best tool I have is a small belt sander this is used for sanding back a couple of mm to the line if needed this depends on what material / boards you are cutting because some leave very small cut splinter's on the boards.
If you use a straight edge you can use the small plunge saw for cutting all sheet materials followed by the sander if needed.

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[Argar]

Tool wise I use various saws for cutting etc.Fav Wise i have a small plunge saw with a 4inch blade a larger one (track saw) also for cutting sheet stuff. Multi tool/ buzz saw but use it very carefully, and sharpen a used saw blade (like a chisel) for seperating stuff. The best tool I have is a small belt sander this is used for sanding back a couple of mm to the line if needed this depends on what material / boards you are cutting because some leave very small cut splinter's on the boards.
If you use a straight edge you can use the small plunge saw for cutting all sheet materials followed by the sander if needed.

Hi Terry any chance you can post a link to the small plunge saw and track saw you've got?

 

[Johnenigma]

Hi,

With the bonding adhesive between the wood and aluminium, I suspect you'd be OK. The van I'm working on is a GRP exterior so not an issue!

A very informative post now I have got started on my project, it is making more sense about what I have become involved with. My motorhome is aluminium skinned but the back is GRP. The wooden frame, I think was poorly constructed from new. I can't see between the GRP and frame but feels like they used double sided tape not adhesive, consequently the back of the motorhome was held on by the 4 sides. Any recommendations for a wood to GRP adhesive?
Thanks for any help and advice.

 

[Argar]

A very informative post now I have got started on my project, it is making more sense about what I have become involved with. My motorhome is aluminium skinned but the back is GRP. The wooden frame, I think was poorly constructed from new. I can't see between the GRP and frame but feels like they used double sided tape not adhesive, consequently the back of the motorhome was held on by the 4 sides. Any recommendations for a wood to GRP adhesive?
Thanks for any help and advice.

Johnenigma Glad to hear you're finding it useful! I'm using Sikaflex 522 for bonding the GRP to wood.

 

[TheBig1]

Any recommendations for a wood to GRP adhesive?

gorilla glue or a trade urethane glue, same thing but cheaper alternative. Very strong bond and perfect on wood joints too as it uses any dampness to foam slightly and has a capillary action bonding into the wood

 

[Terry]

Hi the best / cheapest that works / is Puraflex40 from Toolstation under a £5 a tube sticks anything and half price of Sikaflex. ( Also made by them ) Where things are stuck with double tape use a length of wire like a cheese wire
I think Lidle are doing a cheap Parkside 4ins plunge saw at the moment, will do what you need My tracksaw was +£600 so not needed Small belt sander was about £50 get 80 grit belts,on thin boards it's like using a power plain but very controllable

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