Dampness project - Floor now

[DJL220]

Hi Funsters

Following on from my previous damp project (https://www.motorhomefun.co.uk/forum/threads/dampness-project-roof-first.205004/) I am now about to resolve the floor dampness issues on our Bessacarr E795.

I am reaching out to the wealth of knowledge in this forum and will again show pictures and progress in case anyone else feels like saving money and having a go! This is going to be split into two projects "side" and "rear". How lucky am I to have two more projects!

Side Project
The floor under the O/S from front to rear is showing signs of the dreaded moisture ingress approx 2.4m in length. The dampness is around 6-12" away from the side skirts depending on area. The floor in question is a single ply flooring and access can be had from underneath and in certain areas above. looks like I will need to remove the side skirts and reseal this when refitting.

Lets tackle the questions I have which regarding the damp/spongy floor: -

1) The ply has been painted black and I will need to match this on the replacement flooring. Searching the forums has thrown up more questions than answer including a reply from Swift saying use any black water proof paint.
Anybody have an idea of what to use?

2) The current sheets of ply run across from side to side. I do not need to replace the whole sheet so I was planning on joining the plywoods together using a water proof glue, sealing the cut edges and then biscuits or dowels for extra strength. As the damage is only approx 6-12" will a small piece say 12" wide by 2.4m joined to the existing wood be suitable and strong enough?

3) What to use on resealing the skirts on re-assemble. My favorite Sika 512 or Hodgsons Seamseal CV? I used the later on the top of the skirts but have found it to discolour really quickly, any advice on any other product on the top?

4) Which ply to use on replacement external grade, WBP, marine etc

Rear Project
This is a smaller project and should only require part of the side ply replacing around the rear external door/water tank area. I will tackle this at a later stage ;-)

Thanks in advance

Darren

 

[deleted-member02]

1) The ply has been painted black and I will need to match this on the replacement flooring. Searching the forums has thrown up more questions than answer including a reply from Swift saying use any black water proof paint.
Anybody have an idea of what to use?

I use Rustins Matt Black for the underside of my Hymer.
It appears to be a close match to the original paint and certainly weathers well.

Good luck with the repairs

 

[DJL220]

Initial strip down complete including side skirt off and I was wrong about the ply being painted. It looks like I have a swift vehicle with the vinyl or plastic coating over the plywood. Which I now know was common around 2005-07

Well 14 years later and the results of swift fitting this sheet is a floor that has rotted nicely along the skirt edge and further inwards than I first thought.

This may be again a bigger job than I first thought

Have now removed the furniture from above the first section and need to plan my replacement of this rotten ply.

All will be answered when I strip back further later on.

 

[sweetie]

When Swift repaired the ply on our Bessacarr a few years ago the ply was removed up to the main chassis on both sides also the styrofoam and new foam and ply bonded to floor layer of ply which was still ok. I don’t think they removed any furniture. They ply was crap what they used and repair was so poor we had no confidence in repair sold it back to dealer we bought it from.
I would use a marine ply and make sure all edges are well sealed, also side skirts.
I do not know what type of adhesive would be used to bond styrofoam and ply together.
I hope this might help a little.
Steve

 

[DJL220]

When Swift repaired the ply on our Bessacarr a few years ago the ply was removed up to the main chassis on both sides also the styrofoam and new foam and ply bonded to floor layer of ply which was still ok. I don’t think they removed any furniture. They ply was crap what they used and repair was so poor we had no confidence in repair sold it back to dealer we bought it from.
I would use a marine ply and make sure all edges are well sealed, also side skirts.
I do not know what type of adhesive would be used to bond styrofoam and ply together.
I hope this might help a little.
Steve

Thanks Steve
Need to replace some of the wallboard due to the water ingress being pretty bad and left for 14 years. Hence I have removed the internal furniture. I have yet to peel the plastic/vinyl sheet all the way back to check how bad or how far the rot has gone. Was thinking marine ply and then coat it with a water based protection layer so it can breathe and dry

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[Terry]

If you use Buffalo / type board and seal cut edge's it's gteed for 5 years underwater I would also use Puraflex 40 as sealent / adhesive.

 

[Arthur01]

Hi
an enquiry to Adi4 on here may be helpful, he has just removed the slide out from our RV and replaced the complete floor (about 4m long) of the slide. He manufactured the floor with a build up of marine ply & fibreglass sandwiched between layers. He has a wealth of knowledge coming with a marine background too.
so with regard to water durable adhesives and sealant he is the man to advise.

adi4

www.motorhomefun.co.uk

 

[Gromett]

Have you considered fibre glass and epoxy coating? I believe this is what is used for water tanks and boats.

I have been following a channel on youtube called Boatworks Today.

BoatworksToday

Repairing boats for a living is what I do. Fiberglass, gelcoat, paint and woodworking are my specialties. Basically if it deals with making a boat look it's ...

www.youtube.com

He covers a lot of fibre glassing and epoxy over wood.

My view is this. If you have dry wood then you want the best coating possible to prevent water ingress. If water is already in there, then you either want to leave it to breathe or dry it out then fully seal it.

I am no expert on this though, that is just my opinion. I would considered fibreglass though as it is extremely durable, water tight and tough for protection against impact or intrusion from underneath.

 

[DJL220]

The moment you know there is no turning back!

The side construction is missing as you can see from the rotten timber which has just fallen out and left a big hole. The dampness has gone up the wall and will need cutting out and replacing.

The underneath once the covering was removed shows the hidden issues when water is trapped next to wood for 14 years with no route to escape.

At least the dampness only goes back around 0.5m along the side of the vehicle, checking with a damp meter shows readings of 10-15% and solid wood. What has left me puzzled is the construction used by swift to join the walls and the floor. The first part was just rotten so I had to cut a piece of the floor out to understand the methods used in 2006.

Cut away of flooring above. My understanding is the floor and wall construction are something like the rough sketch below, more investigation is required to fully understand the make up and how i'm going to put things right! I think the foam is bonded to the pine which is then sandwich and bonded to the ply wood upper and lower. The wall construction is pine timber frame with ply either side of the insulation.

The sides and the floor only seem to be held together once the side skirts are screwed on as I am unable to find any other fixings?
All in all there is a lot more to put right here than I first thought, however I do not need to rip the internal floor up too much and can bond the ply back to the metal. Not sure about the underneath as yet, hopefully that there is some metal to bond the new ply to otherwise I will need to bond it direct to the existing foam (which I can see will be painful in the removal process).

If anyone has undertaken anything like this and has words of advice, please feel free to let me know.

Many thanks

Darren

 

[haganap]

good luck mate. I love watching your projects. Done a few damp jobs myself over the years. Nothing of the degree you do though. I tell you one thing, theres a massive market for it.

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[DJL220]

good luck mate. I love watching your projects. Done a few damp jobs myself over the years. Nothing of the degree you do though. I tell you one thing, theres a massive market for it.

My next MH I will fully inspect for dampness and then get a professional to double check
If I knew as much this time last year I wouldn't have brought this MH, I'm fairly handy at DIY and can't justify spending thousands getting my Bessie repaired. At least when I come to sell her I can point people in the direction of these posts
Don't fancy doing this for a living though getting to old to be laying under MH's

 

[Gromett]

Cut away of flooring above. My understanding is the floor and wall construction are something like the rough sketch below, more investigation is required to fully understand the make up and how i'm going to put things right! I think the foam is bonded to the pine which is then sandwich and bonded to the ply wood upper and lower. The wall construction is pine timber frame with ply either side of the insulation.

The sides and the floor only seem to be held together once the side skirts are screwed on as I am unable to find any other fixings?

To be fair to them. If you are constructing from ply and need a sheet of insulation between then that is a logical way to do it. The ply/insulation/ply sandwich should be bonded to each other across their entire surface and this composite structure would be very strong and pretty light at an affordable price. The timbers should be screwed into the ply then screwed to each other along with some adhesive. It would be structurally strong if moisture is prevented from getting in.

The problem seems to me that they haven't done a good enough job on the engineering of the moisture protection.

If I was repairing this I would look to using the same technique but i would use hardwood for the timber. However, I would do a lot more to prevent it happening again.

Is it possible they didn't seal the tops of the outer trim and this allowed water down the inside of it and rusted out the screws and allowed water into the timber?

 

[Terry]

For bonding sheet material I would use Evostick but depending on what you use (Styrofoam/polystyrene)it can melt / attack some material so a test bit should be tried .If it does melt then ring Bostick to see what they suggest.
When your van was built the walls were simply sat onto the floor ......have a search on here about Swift rotting floors on 2005 / 2007 also on some 2009 models

 

[irnbru]

I enjoy looking at the pictures. You really are pretty handy. Do you think £££cost to buy then time and £££ of repair materials you were diddled or was it sold cheap due to the damp?. I'm just being a typical nosey woman In any case you will be able to admire Bessie with pride knowing you've done all the hard graft yourself. Well done this far.

 

[DJL220]

To be fair to them. If you are constructing from ply and need a sheet of insulation between then that is a logical way to do it. The ply/insulation/ply sandwich should be bonded to each other across their entire surface and this composite structure would be very strong and pretty light at an affordable price. The timbers should be screwed into the ply then screwed to each other along with some adhesive. It would be structurally strong if moisture is prevented from getting in.

The problem seems to me that they haven't done a good enough job on the engineering of the moisture protection.

If I was repairing this I would look to using the same technique but i would use hardwood for the timber. However, I would do a lot more to prevent it happening again.

Is it possible they didn't seal the tops of the outer trim and this allowed water down the inside of it and rusted out the screws and allowed water into the timber?

Hi Gromett
Thanks for your thoughts.
As always I have a rough plan for putting her back together, reaching out on this forum really helps to cement my thoughts. Like you I was thinking hardwood for the structure, I will use stainless steel screws and ensure that the water doesn't come in from the skirts. Bonding the ply wood as a sandwich shouldn't be to difficult to re-do with a little preparation and I will use buffalo board underneath.
I'm sure that the previous roof leak had something to do with the rot as well as the skirts not being sealed during manufacture. The previous owner had done some sealing, however I think the damage was already done.

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[DJL220]

For bonding sheet material I would use Evostick but depending on what you use (Styrofoam/polystyrene)it can melt / attack some material so a test bit should be tried .If it does melt then ring Bostick to see what they suggest.
When your van was built the walls were simply sat onto the floor ......have a search on here about Swift rotting floors on 2005 / 2007 also on some 2009 models

Good shout Terry on doing a test I have a small piece to practise on. I think the evo stick I have is the solvent free version. It's funny you only find out all of the info about a MH when things go wrong. As this is my first MH I will definitely do further research when I finally sell Bessie on and buy another one

 

[DJL220]

I enjoy looking at the pictures. You really are pretty handy. Do you think £££cost to buy then time and £££ of repair materials you were diddled or was it sold cheap due to the damp?. I'm just being a typical nosey woman In any case you will be able to admire Bessie with pride knowing you've done all the hard graft yourself. Well done this far.

Pretty sure the novice purchaser (a year ago) brought the wrong MH! I checked the van with a damp meter but missed the spot I am repairing now. I even tapped and proved the floor from underneath but it didn't feel that bad.
The materials will cost a few £'s and as you say at least I will know the job is done.

 

[DP+JAY]

I've done it & find this to be the best glue.

https://rover.ebay.com/rover/1/710-...0001&campid=5338547443&icep_item=153923979833
Sticks well to the outer skin too.
DP

 

[DP+JAY]

I've done it & find this to be the best glue.

https://rover.ebay.com/rover/1/710-...0001&campid=5338547443&icep_item=153923979833
Sticks well to the outer human skin too.
DP

Just make sure you have plenty of disposable gloves& use them, it's very difficult to remove from human skin.

 

[DJL220]

Just make sure you have plenty of disposable gloves& use them, it's very difficult to remove from human skin.

Thanks for the advice, have purchased a bottle and will let you know how I get on. Lucky I have loads of gloves too

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[Gromett]

Hi Gromett
Thanks for your thoughts.
As always I have a rough plan for putting her back together, reaching out on this forum really helps to cement my thoughts. Like you I was thinking hardwood for the structure, I will use stainless steel screws and ensure that the water doesn't come in from the skirts. Bonding the ply wood as a sandwich shouldn't be to difficult to re-do with a little preparation and I will use buffalo board underneath.
I'm sure that the previous roof leak had something to do with the rot as well as the skirts not being sealed during manufacture. The previous owner had done some sealing, however I think the damage was already done.

I am in awe of your skills, perseverance and patience on this project. Far bigger than I would have taken on...

Can I suggest you do look at fibre glass and epoxy as a means of protection and structural integrity. I suspect that you may find it useful in rebuilding and protecting. The beauty of the technique in my view is that it not only provides structural integrity at the joins but it also seals the wood and prevents any further ingress. You can get epoxies that will soak into the end grain of lumber and into the edges of ply which combined with the fibre glass would do an amazing job at protection will strengthening.

The boatworks today link I gave in a previous post is worth giving an hour to. You may rule it out, but the techniques I am sure you will find interesting. In many videos he does epoxy over ply. But I have seen his use the technique to make foam based and even balsa wood composites for structural stuff.

Good luck with your project and I hope this bit finally sees the end to your hard work and you can start using your van to it's fullest.

 

[DJL220]

I have a question about joining plywood to the existing ply underneath the MH once I have cut out the rot. After further inspection the ply top and bottom of the sandwich is only 6mm thick and so rules out biscuit joints or dowelling.
The top ply is only going to be cut back by approx 300mm from the wall and underneath around 500mm. Thought it would be best to stagger the cuts too.
What is the best way to join without losing too much strength in the floor? The only good thing is that the area of floor is under the sofa and not a walkway.

Options I can think of are: -
simple butt joint
Butt joint and bond in thin aluminium under both sides of the joint (that's the method on the top side)
Lap joint ( difficult to do well underneath the MH)
Attach aluminium plates underneath and bolt through the floor (risk of dampness!)
Dish out the wood and use fibreglass and/or epoxy
Worse case replace the whole floor

Someone out there must have done this before and I really could use a steer on this one.
Thanks guys

 

[68c]

I did a similar repair to a 1999 Swift Sundance about three years ago. I found the metal sheet is only about 2" x 6" and was placed in strategic positions to give something for the internal furniture to be screwed to, I just used thicker ply so did not refit the metal. I followed boat repair techniques having repaired an old plywood Mirror Dinghy. Epoxy resin works much better than fibreglass polyester resin although it is dearer. You can get a very thin epoxy resin, almost like white spirit, that will soak into the rotten wood. Keep applying it until no more will soak in. Being a two part resin and hardener system, It will then set chemically and reinforce the wood. Repair sections of wood can be pretreated with epoxy resin and bonded in with a thicker resin. Epoxy resins stick very well to themselves. You can get a powder filler that you mix with the resin to make it as thick as want. The epoxy resin can be used on the foam insulation, it will not dissolve it. An old caravan repair method for delaminated floors was to drill lots of holes and inject the resin to stiffen the whole thing up. Read up on boat repairs, not surprisingly they also suffer from damp problems.

 

[TheBig1]

butt joint the ply, stagger the cuts to retain integrity and bond an extra strip of ply over the exposed joint underneath before sealing it all. Use 2 part epoxy glue to rebond the sandwich, which is what was used originally. Only knock up enough glue to bond the part you are working on and can use in about 8-10 minutes max. once set, it's a good permanent bond

If you can't sort good hardwood then use treated timber for the structural bits and again epoxy and screw it in place

 

[Gromett]

I did a similar repair to a 1999 Swift Sundance about three years ago. I found the metal sheet is only about 2" x 6" and was placed in strategic positions to give something for the internal furniture to be screwed to, I just used thicker ply so did not refit the metal. I followed boat repair techniques having repaired an old plywood Mirror Dinghy. Epoxy resin works much better than fibreglass polyester resin although it is dearer. You can get a very thin epoxy resin, almost like white spirit, that will soak into the rotten wood. Keep applying it until no more will soak in. Being a two part resin and hardener system, It will then set chemically and reinforce the wood. Repair sections of wood can be pretreated with epoxy resin and bonded in with a thicker resin. Epoxy resins stick very well to themselves. You can get a powder filler that you mix with the resin to make it as thick as want. The epoxy resin can be used on the foam insulation, it will not dissolve it. An old caravan repair method for delaminated floors was to drill lots of holes and inject the resin to stiffen the whole thing up. Read up on boat repairs, not surprisingly they also suffer from damp problems.

I would follow this advice. In addition if possible you could use a multi tool to create castellations in the ply to increase the surface area of the join then place a strip of aluminium over the entire length of the castellated joint bonded with epoxy and fibreglass.

The castellations would be even better if you can get access to the top of the joint as you could then apply the epoxy fibreglass to the top as well as the bottom. The joint would then be stronger than the wood itself. You could then skip the aluminium strip.

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[DJL220]

I did a similar repair to a 1999 Swift Sundance about three years ago. I found the metal sheet is only about 2" x 6" and was placed in strategic positions to give something for the internal furniture to be screwed to, I just used thicker ply so did not refit the metal. I followed boat repair techniques having repaired an old plywood Mirror Dinghy. Epoxy resin works much better than fibreglass polyester resin although it is dearer. You can get a very thin epoxy resin, almost like white spirit, that will soak into the rotten wood. Keep applying it until no more will soak in. Being a two part resin and hardener system, It will then set chemically and reinforce the wood. Repair sections of wood can be pretreated with epoxy resin and bonded in with a thicker resin. Epoxy resins stick very well to themselves. You can get a powder filler that you mix with the resin to make it as thick as want. The epoxy resin can be used on the foam insulation, it will not dissolve it. An old caravan repair method for delaminated floors was to drill lots of holes and inject the resin to stiffen the whole thing up. Read up on boat repairs, not surprisingly they also suffer from damp problems.

Thanks 68c for your detailed advice. Have had a look at boat building this morning and think the West system epoxy fits the bill nicely. Will go for the longer working time 105 + 206 mix with filler as needed. I will make a lap joint on the lengths and butt up against the widths and coat with epoxy during and after completion.
My Bessie still has the original ply covered with the vinyl sheet acrosss the rest of the flooring, would it be worth removing all of this and epoxying the whole floor before painting? I really doubt that the ply is marine grade when built in 2006.
Thoughts?

 

[DJL220]

butt joint the ply, stagger the cuts to retain integrity and bond an extra strip of ply over the exposed joint underneath before sealing it all. Use 2 part epoxy glue to rebond the sandwich, which is what was used originally. Only knock up enough glue to bond the part you are working on and can use in about 8-10 minutes max. once set, it's a good permanent bond

If you can't sort good hardwood then use treated timber for the structural bits and again epoxy and screw it in place

Thanks TheBig1
Struggling to find wood of the right size in hardwood and no longer have all my old woodworking equipment Didn't have the room in the garage!
Will try and complete a lapjoint on the ply lengths and butt joint the sides with epoxy. Might have to use treated timber as it's the nearest size I can get for the structure

 

[DJL220]

I would follow this advice. In addition if possible you could use a multi tool to create castellations in the ply to increase the surface area of the join then place a strip of aluminium over the entire length of the castellated joint bonded with epoxy and fibreglass.

The castellations would be even better if you can get access to the top of the joint as you could then apply the epoxy fibreglass to the top as well as the bottom. The joint would then be stronger than the wood itself. You could then skip the aluminium strip.

Have the multi tool at the ready and has been used loads in the MH so far! Had a look at the YouTube videos on boat repairs this morning and with the help from the guys on here now have a plan.

 

[68c]

Perhaps you could chamfer or taper the edges of the old and new wood to give a wider contact area, its called a Scarfe joint, lots of info on Google. Will the repair area be visible after the repair, if not any vinyl off cut would do. In my case I had removed all the internal furniture so I lai d a new sheet of vinyl across the whole floor.
I took the opportunity to put a 'drain' hole under the toilet/shower area, similar to a gas drop out, just in case I had a future leak in that area.

 

[DJL220]

Perhaps you could chamfer or taper the edges of the old and new wood to give a wider contact area, its called a Scarfe joint, lots of info on Google. Will the repair area be visible after the repair, if not any vinyl off cut would do. In my case I had removed all the internal furniture so I lai d a new sheet of vinyl across the whole floor.
I took the opportunity to put a 'drain' hole under the toilet/shower area, similar to a gas drop out, just in case I had a future leak in that area.

This is the underneath of the MH as you can see I have cut away the waterproof barrier (some form of vinyl I think).
It's really thin but has caused a lot of issues on my MH.
I was thinking of removing all it and coating in epoxy and then painting with a black paint.
Have already cut the vinyl flooring inside and will replace this at a later stage of the project ;-)

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