Dampness project - Roof first (1 Viewer)

[DJL220]

Hi

Within this thread I will document what I find as our Bessacarr MH failed on a recent Hab check for dampness. The ceiling has started to go spongy after our first trip away. We purchased the MH around 6 weeks ago and the owner stated that the leak in the roof had been resolved as the ceiling was a little spongy and showing readings of around 10-15% when checked. Well that appears not to be the case as the readings around the skylights are now showing 30-45%. I knew when we purchased it I would need to undertake a ceiling re-paper, what I did know at the time was how badly damaged the vehicle was going to be.

Thankfully there are forums like these on the web and after reading the thread by The_Kraken "My DIY dampness project" and being quoted around £10k for just the labour I thought I would have a go!

Any help, guidance and advice will be gratefully received by the wider community.

Any

 

[Riverbankannie]

Wishing you good luck with the project, the MH looks lovely and, although I know you certainly didn’t expect this it’s good you are having a go.

 

[DJL220]

1) investigation of roof

So I thought I would start be taking the roof light covers off and see if I could see how bad the leak would be. At this point I was in two minds as to whether to attempt the repair or not. Pressing onwards I started to remove a little of the ceiling paper only to be confronted with my worse nightmare, water and a lot of dampness.

Looks like someone used gaffer tape as a repair method! Well I thought I would continue to see how far the water had travelled around the roof space. Looking at the next picture you can see it has travelled a fair distance.

Further ceiling removed trying to find the leak and also the edge of the dampness. At this point the top layer of ply was failing apart as I touched it. My worst feelings ever that I have unearthed a massive issue with our MH and brought a money pit! What I thought would be a quick repair has escalated into a huge strip down. So from what I can see so far the building of our MH is based upon a layer of ply bonded to the roof. This is glued to polystyrene insulation, in places there is a thin sheet of aluminium bonded to the foam and then the ceiling board on top of this. Not a great deal of timber supports anywhere? Glad I haven't walked on this roof so far!

Not clear in the next picture but the frame around the rooflight is a hard wood and then a softwood is attached to and to the outer frame. In my case the softwood has rotted through. I had to take the side cupboards down to strip back more ceiling, this was a painful process as I couldn't find that one hidden screw attaching the pelmet ?
The tv cupboard was taken apart too, however the top was a pig to remove as this was stapled from the top during the manufacturing process. These forums are great for finding out this information, hopefully people will find my thread useful too.

I have propped the ceiling up, because it dropped down slightly when the ceiling board was removed and the softwood split, can do without further damage.

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[SuperMike]

I know as a private purchase, buyer beware comes into it, but even then sellers are not allowed to make a statement that they know to be untrue. He/she said it had been resolved and clearly that is not the case. I would pay the seller a visit, to discuss things.

 

[gus-lopez]

& good luck with it. Keep us up to date & ask away

 

[DJL220]

I know as a private purchase, buyer beware comes into it, but even then sellers are not allowed to make a statement that they know to be untrue. He/she said it had been resolved and clearly that is not the case. I would pay the seller a visit, to discuss things.

I know buyer beware, I have responded to the previous owner and he stated that it was repaired a few years ago and could have failed. He wasn't aware of the failure! When I was asking for quotes one of guys said to put it on eBay and sell it onwards!
We love Bessie and I think I will be able to repair her to good health with the help of forums and the lovely people out there. Plus it wouldn't sit well with me selling a MH with issues.

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[Late Starting]

Best of luck with your repair have had problems like that many years ago and worked slowly through them
there was no such thing as forums then so chin up and just keep going forwards slowly and safely.
The BEST THING you can do is PAY a membership fee of £15.00 to get unlimited help from some very helpful
and knowledgeable people.
Cliff

 

[138go]

If you have a look at how they are built you will find the roof goes on last. This can create all sorts of problem when it comes to repairs. As has been said before on this forum if you view a MH that has / is damp ..

RUN

 

[DJL220]

Best of luck with your repair have had problems like that many years ago and worked slowly through them
there was no such thing as forums then so chin up and just keep going forwards slowly and safely.
The BEST THING you can do is PAY a membership fee of £15.00 to get unlimited help from some very helpful
and knowledgeable people.
Cliff

It took a while to work out what you meant . Have now joined so I can post again!

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[DJL220]

If you have a look at how they are built you will find the roof goes on last. This can create all sorts of problem when it comes to repairs. As has been said before on this forum if you view a MH that has / is damp ..

RUN

A little to late for this i'm afraid, lesson learnt for next time though!

 

[Vipar]

Maybe a local coachbuilder could give you a few tips for a couple of pints?

 

[mitzimad]

Theres several thread on here where people have repairs serious damp try a search

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[DJL220]

2) Update on roofing issues.

Finally managed to remove all of the damp insulation, ply wood and ceiling as you can see from the picture below. removing the plywood stuck to the out roof was a nightmare and took ages. I ended up using a multitool with a blunt blade to aid the removal. It was going really well until I caught the roof and created an extra hole!!! It has been sunny for days so i got away with that (just).

I then removed the ply wood support around the vent, which was just as well due to the dampness in the wood.

Once the plywood was off, it just left all of the adhesive to remove, again this was painful until I brought a window scrapper from Screwfix.

I also believe I have found the leak! you can see the crack in the photo below.

This has now been fixed with a fibreglass repair kit, alongside the extra hole I made for myself.

I have also brought some filler for the roof as the crack appears to have been filled but is still letting water through. I needed to remove the skylight to check if the crack needed extra filling too. This is what i found once I spent 3 hours slowly removing the adhesive. The white filler in the distance needs to be sanded back to blend in with the roof. This will be done soon.

 

[TheBig1]

I know it's easy said, but slow down. The more you pull apart the weaker the structure.

first off seal the leak to stop any more water ingress. you will need to remove the skylight and refit with fresh mastic and framing battens. put planks across the roof to spread the load if you get up there and stay near the walls. you will also likely have a strip covering the joint between the overcab and roof. renew that too and inspect the roof surface for corrosion and pin holes

the roof can be painted with tanking paint to seal it. then let it dry out with warm air and airflow. once down to 15%, find the extent of the damage carefully. remove rotten ply to a straight line across the roof

reboard with the correct coated ply, bonded on with 2 part adhesive, keeping the new board supported as the glue sets. trim the joints with matching cover strip and rebuild cupboards

Shouldn't take too many man hours and patience waiting for it to dry

 

[TheBig1]

i was slow typing above, there is a lot of damage there, and the slits in the aluminium outer skin need over plating. just filler and fibreglass won't work

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[DJL220]

3) Roofing update - Weekend working

So I have managed to clear out all of the rotten timber at the back of the motorhome and have finally started to make the repair. I have bonded plywood back to the outer roof using Sika 512 and held this with wood battens and supports (overnight). This has now replaced a little rigidity to the roof.

Next job was to cut in and replace the frame round the skylight. I had some oak flooring left over and this is the correct width for the frame work. I cut this down to size, removed a little more of the right hand side framework. Then using a dowel and pva wood glue I joined these back together. Sika 512 was used to fix to the roof. The picture below is the most current photo and will be left like this until I next have time to work on Bessie. The roof structure has now gone really nice and solid.

Next jobs: -
1) install the new roof light (should arrive this week). Ordered as i'm not 100% sure that this has been damaged by the previous owner.
2) install the polystyrene insulation - i was thinking of using either pva wood glue or sika 512. Anyone have any suggestions please?

The weather has finally turned after days of sunshine so Bessie has a temporary roof as I haven't re-sealed the old skylight firmly. In fact I have used half a roll of gaffer tape around the outside and thought the tarp was needed. you can just see my 3 supports under the tarp as I had pooling of water when it rained.

 

[DJL220]

i was slow typing above, there is a lot of damage there, and the slits in the aluminium outer skin need over plating. just filler and fibreglass won't work

It's strange as the roof doesn't appear to be aluminum more just like GRP. i thought the fibreglass and filler would be enough. If it is Aluminium it is only a few micron thick!

The only aluminium I found was between the polystyrene insulation and the ceiling board. not sure if you can see more from this photo?

I plan to re-bond 0.9mm Alu when I refinish the internal roof. My plan was to rebuild in reverse of the original build.

 

[DJL220]

This is the make up of the underside of my roof. The bottom ply is the ceiling on show, then you have the aluminum (.75mm thick), bonded to the insulation which is then bonded to more ply which is fixed to the out roof.

The two posts above are a overview of the past 7 days.

TheBig1 whats your thoughts on the above?

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[TheBig1]

it looks like bessacar used a pretty bog standard layered composite panel. less common to have aluminium facing on the bottom of the roof

The external roof skin does indeed appear to be a grp capping. at a guess I would suggest somebody stood on the roof too near the rooflight opening causing a tear. that needs grinding out and repairing with resin and gelcoat. the filler may easily crack with movement

 

[funflair]

I'm sure the whole roof will be a moulded fibreglass panel, the only thing that makes it waterproof is the gel coat on the outside so it's worth making sure that is intact and if the filler isn't waterproof it would be worth putting gelcoat over it, I think TheBig1 is right that it will have been caused by being walked on and to be honest I would be very careful walking on that type of roof.

Martin

 

[MisterB]

i would have drilled a small hole where the crack stops - this would be to prevent the crack from ever starting again from that point onwards. its a trick ive seen used on bumper repairs etc on tv programmes (and once on an antique repair programme) of course you need to fill the drilled hole afterwards

looks like youre getting on with the repair nicely - thanks for sharing with everyone and i am pretty sure the project will be followed by others with a similar problem in the future.

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[DJL220]

I'm sure the whole roof will be a moulded fibreglass panel, the only thing that makes it waterproof is the gel coat on the outside so it's worth making sure that is intact and if the filler isn't waterproof it would be worth putting gelcoat over it, I think TheBig1 is right that it will have been caused by being walked on and to be honest I would be very careful walking on that type of roof.

Martin

I used plastic padding gel coat filler, thought this should repair the roof nicely with the fibre glass area patched underneath. I think the previous owner tried to remove the skylight and could have damaged the corner at this time. He had used a clear filler/sealer which appears not to have worked. I sanded a groove into this and the surround area before applying the gel coat filler. Fingers crossed I have done the right thing so far?

Plastic Padding Gelcoat Filler Tin 241g White GRP Fireglass Boat Caravan Repairs | eBay

PLASTIC PADDING GELCOAT FILLER. This high quality fine white filler repairs and fills sets in just 10 minutes, and can be polished to a gloss finish or can be painted over.

rover.ebay.com

 

[DJL220]

i would have drilled a small hole where the crack stops - this would be to prevent the crack from ever starting again from that point onwards. its a trick ive seen used on bumper repairs etc on tv programmes (and once on an antique repair programme) of course you need to fill the drilled hole afterwards

looks like youre getting on with the repair nicely - thanks for sharing with everyone and i am pretty sure the project will be followed by others with a similar problem in the future.

That's a good idea ref drilling of a small hole at the end of the crack. If I oversand the area and need to start again then I will drill a hole. This is a warm up for the other skylight as this needs taking out and re-sealing too! Trying not to take too much of the MH apart at anyone time as per TheBig1's comments. The structure would be too weaken otherwise
These forums are great for help, support and ideas - thanks to all ?

 

[Happy Jim]

I sanded a groove into this and the surround area before applying the gel coat filler. Fingers crossed I have done the right thing so far?

Plastic Padding Gelcoat Filler Tin 241g White GRP Fireglass Boat Caravan Repairs | eBay

PLASTIC PADDING GELCOAT FILLER. This high quality fine white filler repairs and fills sets in just 10 minutes, and can be polished to a gloss finish or can be painted over.

rover.ebay.com

Yes, you’re doing it right! Glass fibre underneath for strength, drill hold end of crack, dig out the crack then Gel - Jobs good Sir!

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[DJL220]

Nightmare today, as I had only temporarily refitted the old roof light and covered with tarpaulin the worst thing happened. The sky dropped huge amounts of rain in a few moments, drips everywhere inside around the skylight ?
Lucky I have marquees so covered the roof with part of this and the water stopped!

New skylights arrived today and I now have a dilemma: -
What to use as a sealant? My plan was to use a W4 - 19mm sealing strip, the new light has a small gap which is less than 19mm and then a secondary rubber seal. Should I cut the strip width or use a different cartridge type sealant?

Thoughts from you guys out there who have done this before, what would you suggest?

 

[Happy Jim]

Sikaflex 512 or EBT

Rgds

Jim

 

[HandyAndy]

Second the sika. Sticks like *** to a blanket! ??

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[tonyidle]

Don't use Sika to seal anything that may need to be removed. For sealing an adhesive isn't required. Butyl mastic strip or gun - your choice - is an excellent option. I've always used the strip and have had no failures to date.

 

[tonyidle]

Consider Kingspan as insulation. It's brilliant stuff and easy to work with. If bonded rather than laid in it will add considerably to overall strength.

 

[CazPaul]

I second don't use sika for roof light fitting, Hodgsons seamseal cv is good stuff.

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