Vernon B Posted August 31, 2007 Share Posted August 31, 2007 Terry following your interesting comments under the "damp testers" thread I wondered if you could shed any light on a problem I've had for a couple of years. Having experienced a number of water ingress problems when the van was new I armed myself with one of those inexpensive two pronged damp meters and now carry out regular checks. The thing is I'm getting high audible readings (certainly in excess of 20%) under certain conditions in an area of the roof lining above the drop down bed in this A Class. The roof lining is a soft fabric with a sponge membrane, only about 4mm thick, and it is bonded directly to the GRP front shell of the van. That shell has some cavities in it and is about 30mm thick. The readings are only present when it has rained and/or when relative humidity is above 65%. Now the dealer has confirmed that my readings are correct but having carried out extensive tests/experiments we're both of the opinion that the moisture is a result of some form of condensation rather than ingress. I should also say that even with extremely high readings the surface can be "dried out" very quickly with a small amount of heat - ie a 500w oil filled radiator placed 40cm under the area for 10/15 minutes. ["Dried out" is not a good term because the surface feels "cold" rather than "wet" to the touch and little different to other parts of the lining near by.] Although I accept that condensation is the most likely explanation I can't square that with the facts that:- a) It only occurs on one side of the roof and not the other - which is also exposed to vitually identical conditions b) It occurs on a surface which has some form of insultated backing but not on the adjacent cab windows which are exposed to the elements c) It responds to the application of heat but is not remedied by plenty of fresh air So I wondered if you had any thoughts and particularly if, given the surface involved, damp meters could give rogue readings. Thanks Vernon Link to comment Share on other sites More sharing options...
Old Git Posted August 31, 2007 Share Posted August 31, 2007 Vernon B - 2007-08-31 4:02 PM a) It only occurs on one side of the roof and not the other - which is also exposed to vitually identical conditions Hi Vernon Terry is the man who knows about these things, but is the "dodgy" area at the head end of the bed? It sounds too simple, but we breathe out a lot more water vapour than you might imagine. Just a thought - I shall be interested to follow the (probably) several diagnoses to the eventual conclusion Regards Dave Link to comment Share on other sites More sharing options...
Vernon B Posted August 31, 2007 Author Share Posted August 31, 2007 No Dave. This happens to be at the foot end, and despite what our feet might give off, it doesn't appear to be related to whether the bed or the van are occupied. This is a real mystery I tell you but I'd welcome any suggestions even that we might be hosts to a weeping Madonna! V Link to comment Share on other sites More sharing options...
Old Git Posted August 31, 2007 Share Posted August 31, 2007 Vernon B - 2007-08-31 4:38 PM No Dave. This happens to be at the foot end, and despite what our feet might give off, it doesn't appear to be related to whether the bed or the van are occupied. This is a real mystery I tell you but I'd welcome any suggestions even that we might be hosts to a weeping Madonna! V I'm disappointed now Vernon. My next comment was going to be about sweaty feet, but you beat me to it. What a spoilsport! Sorry - can't think of any other pearls of wisdom. If it isn't your hot steamy breath you'll have to wait for Terry to log on. Cheers Dave Link to comment Share on other sites More sharing options...
Terrytraveller Posted August 31, 2007 Share Posted August 31, 2007 Hi Vernon, I use the Wagner L609 Moisture detector http://www.woodcraft.com/family.aspx?FamilyID=3208 and this comes with a comprehensive adjustment table for different woods. I have found that some timbers used in MH/caravan construction will give a highish reading on my meter 10% - 14% is not suspicious, generally I look for 4%-8% as normal. Getting back to your problem, it seems you are suffering from condensation. If moisture beads have gathered above the plastic headlining, the meter will give a 22 plus reading on my meter. I have just set up an experiment with moisture beads covering plastic sheeting and the readings went off the end LED, so the reading you are getting is suggestive of the above conditions - try it for yourself. Perhaps you are getting condensation gathering because of airflow between the grp/aluminum roof and headlining. Stopping the airflow or increasing the airflow would help in reducing or stopping condensation occuring. The only other way to stop condensation would be equalise the temperature of the air gap between outer skin and headlining, and the interior, perhaps by gluing 1" polystrene slabs onto the underside of the cab roofing. Regards Terry Link to comment Share on other sites More sharing options...
Charlieme Posted August 31, 2007 Share Posted August 31, 2007 The angle of the vehicle perhaps, moisture rising to the highest point? Is the insulation weaker at that point? Are there holes in that side of any insulation The insulation could be porous on one side Link to comment Share on other sites More sharing options...
davenewellhome Posted August 31, 2007 Share Posted August 31, 2007 Hi Vernon, am I correct in thinking you brought this van to me a few months ago? If so I'm sorry to hear you still haven't resolved this conundrum. I too look forward to seeing what suggestions come up 'cos I'm as baffled as you. D. Link to comment Share on other sites More sharing options...
Vernon B Posted August 31, 2007 Author Share Posted August 31, 2007 davenewell@home - 2007-08-31 7:15 PM Hi Vernon, am I correct in thinking you brought this van to me a few months ago? If so I'm sorry to hear you still haven't resolved this conundrum. I too look forward to seeing what suggestions come up 'cos I'm as baffled as you. D. Hi Dave - it's the very one. I think we should explain that you were doing a couple of other jobs on the van and since I was still in discussions with the dealer I asked you to see if there was anything obviously amiss - your expert eye at least established that it wasn't straightforward. Anyway I thought it would be useful to piggy-back the damp tester thread and it hooked Terry who as you see has come up with some useful observations. So let's see what else emerges here. Regards V Link to comment Share on other sites More sharing options...
davenewellhome Posted August 31, 2007 Share Posted August 31, 2007 Vernon B - 2007-08-31 7:52 PM davenewell@home - 2007-08-31 7:15 PM Hi Vernon, am I correct in thinking you brought this van to me a few months ago? If so I'm sorry to hear you still haven't resolved this conundrum. I too look forward to seeing what suggestions come up 'cos I'm as baffled as you. D. Hi Dave - it's the very one. I think we should explain that you were doing a couple of other jobs on the van and since I was still in discussions with the dealer I asked you to see if there was anything obviously amiss - your expert eye at least established that it wasn't straightforward. Anyway I thought it would be useful to piggy-back the damp tester thread and it hooked Terry who as you see has come up with some useful observations. So let's see what else emerges here. Regards V Quite agree Vernon, your story seemed familiar and when I checked your profile I thought "I know that 'van" (lol) . As I said I'm as intrigued as you are about it. D. Link to comment Share on other sites More sharing options...
Charlieme Posted August 31, 2007 Share Posted August 31, 2007 Does the good side/area have a better air circulation around/through it. Is the moisture the same side as your cooking area? If so moisture from cooking/heating is moving via tunneling or gaps in the interior bodywork and insulation to then collect in one specific area. Also when it rains you say, I assume you have a fridge/freezer, is this the same side as the 'moisture condensation' problem? Is moisture either (a) coming in the air vents then circulating inside the bodywork and rising to the roof by fridge heater or (b) an area above the fridge is becoming 'wet' at times then vapourising due to the workings of the fridge mechanism and then travelling via the interior bodywork to your damp area. You don't say if you are moving or static when the dampness occurs. Moisture (hot or cold) can be funnelled in from the engine compartment and again find its way through the bodywork. The water must start from a warm source such as cooking of fridge working, the vapour then very simply finds its way upwards to a suitable point where you detct dampness. I assume you have a domestic water heater somewhere. When in operation moisture in the air surrounding the heater will rise, finding a path to the top as above. Do you have a leaking hot air system? Finally you should be able to keep a diary of when the dampness occurs coupled with what appliances you've had working that day. It's pretty simple really, hot air rises and condenses when chilled. Link to comment Share on other sites More sharing options...
Vernon B Posted September 1, 2007 Author Share Posted September 1, 2007 Hi C&m that's a pretty thorough/useful checklist. Let's take them one at a time:- On the face of it both sides have the same amount of air circulation. The "damp patch" is on the passenger (left hand) side. This is above a drop down cab bed and the moisture occurs whether the bed is down (as it always is when the van is not in use) or raised. This bed drops really low and produces a very large open area. As for when its closed up, I've put a stack of pillows on the mattress to block the space, and still get these readings. The problem is unassociated with the use of any appliances. It occurs when humidity is high when we are using the van/appliances or when humidity is high when its not use - like at present when its been "off the road" for a month. I get these readings after a run (when the bed is up of course") or when the van has been stationary/unoccupied for a long period. There is no obvious "tunneling/funneling" effect in this area. But it is at ceiling level where the GRP shell probably offers less insulation than the main roof area. There are no roof lights/vents above the bed, but there is a Heki near by. There are no obvious sources of "heat" especially when the van is off the road, although it is not that far from the engine bay and I'm not sure if any "heat" comes off any of the electronics - like the alarm. But the thermometer I have in area does not indicate the presence of such a "hot spot". The van is stored in a south facing position but the problem only occurs on relatively damp/cold sunless days. Its a real "b" isn't it? V Link to comment Share on other sites More sharing options...
Charlieme Posted September 1, 2007 Share Posted September 1, 2007 OK so you're using a meter now but how did you notice it in the first instance? What's a Heki? You filled the immediate space with pillows and it still appeared so it does seem to creep around and through the bodywork Have you tried disconnecting the battery(s) so's to eliminate any heat source. Having said that you would probably have to remove them for a spell. Link to comment Share on other sites More sharing options...
Brambles Posted September 1, 2007 Share Posted September 1, 2007 Hi Veron, Hard to visualise exactly the lay out of your van roof but reading through all your comments I suggest you have an area of damp in an adjacent wall to the side that is showing condensation or a winscreen leak at top. I suspect it is slowly drying out making the air in the roof cavity damp and it is condensing. I think you need to thourally check ajoining walls directly next to the 'damp' roof area. I don't think you have said what your initial ingress of water problems where, but could water from this still be absorbed somewhere and drying out. Also a good check on all exterrnal sealed areas, but assume you have done that. There is no doubt in my mind you have some residual damp or moisture getting in somewhere and you need to find it, try and think laterally, how about any front facing lights attached to top of roof moulding, or mirror bracket, etc. Also check the front windscreen rubber moulding seal is sound and no leaks, remembering the water could get in one side and travel all the way to the other before being absorbed up into the roof lining. Just some ideas!!! If your roof linijg is tucked into the winscreen rubber then my money is on that leaking and being absorbed and evaporating to condense on roof. Jon. Link to comment Share on other sites More sharing options...
Vernon B Posted September 1, 2007 Author Share Posted September 1, 2007 Charlie&me - 2007-09-01 10:15 AM OK so you're using a meter now but how did you notice it in the first instance? What's a Heki? You filled the immediate space with pillows and it still appeared so it does seem to creep around and through the bodywork Have you tried disconnecting the battery(s) so's to eliminate any heat source. Having said that you would probably have to remove them for a spell. These are pretty searching questions C&m you're not a former copper by any chance? A Heki is a brand of large roof light. Mine is situated in the middle of the roof about a metre or so from the area. Heki's allow for some ventilation even when fully closed. How did I first notice it? Longish story but early on there was some staining of the lining. Unfortunately by the time I noticed that it had dried out but nevertheless it was returned to the manufacturers who resealed all critical joints. Following that experience I damp test it regularly, which established that the "thing" hadn't gone away. When readings are v.high I disperse moisture with a low wattage heater. Probably because of that I have experienced no more staining - thus far. Certainly the "pillow test" does suggest ingress from within the body or externally. I should perhaps mention here that the extent of the affected area can increase in size depending upon the magnitude of the readings. The shape of the area is always the same - basically a band running parallel to the side of the 'van, from the start of the cab section down to front. The band can be from 100mm to 380mm wide depending on the readings. I don't have the facilities to put the van undercover but the dealer assures me they have and the high moisture readings do re-present when they've done that. I haven't witnessed that. I have removed some of the internal trim to inspect obvious seepage points and by that I'm pretty convinced that this isn't "normal" ingress. Let me explain that a little further: At first sight the "band" shape of the damp area suggests that the moisture is coming from the seam joining the side wall to the cab roof shell. Now I've removed some internal wall cladding to reveal that the roof lining overlaps behind this cladding forming a 40mm overlap with the wall. This overlap is "bonded" to the wall but strangely never gets "damp". It doesn't even draw the dampness back from the affected area. And remember the lining is a soft fabric with a sponge backing. If water was entering from the side seam it would be impossible for the lining overlap not to get damp. I also considered the possibility of moisture seepage through the GRP shell, by what they call osmosis, but visual inspection of the gell coat has apparently ruled that out. I haven't thought of disconnecting the battery to remove any heat source. So there you go. I don't want to give people the impression I'm inviting solutions in order to take pleasure in knocking them down and I think yours and the other points have been very useful in testing my own thinking and actions. I have formulated a couple of other theories which I'll share a little later, but for now I'd like to see if anything else surfaces. I have 6 months of the ingress warranty to run so if there is a manufacturer's liability here I obviously need to pinpoint it pdq. So far they've relied on their willing, but nevertheless inconclusive, endeavours to placate me. Of course some people might say - "so what, its only a bit of moisture" - but would they be happy to let a potential time bomb keep ticking away? Thanks again for your thoughts. V Link to comment Share on other sites More sharing options...
Vernon B Posted September 1, 2007 Author Share Posted September 1, 2007 Brambles - 2007-09-01 2:59 PM Hi Veron, Hard to visualise exactly the lay out of your van roof but reading through all your comments I suggest you have an area of damp in an adjacent wall to the side that is showing condensation or a winscreen leak at top. I suspect it is slowly drying out making the air in the roof cavity damp and it is condensing. I think you need to thourally check ajoining walls directly next to the 'damp' roof area. I don't think you have said what your initial ingress of water problems where, but could water from this still be absorbed somewhere and drying out. Also a good check on all exterrnal sealed areas, but assume you have done that. There is no doubt in my mind you have some residual damp or moisture getting in somewhere and you need to find it, try and think laterally, how about any front facing lights attached to top of roof moulding, or mirror bracket, etc. Also check the front windscreen rubber moulding seal is sound and no leaks, remembering the water could get in one side and travel all the way to the other before being absorbed up into the roof lining. Just some ideas!!! If your roof linijg is tucked into the winscreen rubber then my money is on that leaking and being absorbed and evaporating to condense on roof. Jon. Good points Jon. I guess it is possible that the original ingress was "sorted" by the factory (see earlier reply to C&m) and that there is still residual moisture in the GRP cavities - but it's taking a long long time to dry out. The winscreen seal is something that neither I or the dealer have considered, and you might be on to something. The winscreen seals are not that impressive and given the configuration of the cab it is possible that the moisture is tracking up from there - very worthwhile checking as its certainly more plausable than the side joints (again see reply to C&m). Me thinks its worth dismantling a few more bits! Good stuff thanks V Link to comment Share on other sites More sharing options...
Charlieme Posted September 1, 2007 Share Posted September 1, 2007 No I'm not a law man, its just that I've been around for 80 years and was at one time a trouble shooting engineer for the motor trade, also worked in the vacuum industry and space research with a variety of gases, air being just one so I've met a number of puzzles in my time. It may be quite simple that the insulation at that point is the weakest link. Suggest making a diary of every move and findings. Link to comment Share on other sites More sharing options...
Clive Posted September 1, 2007 Share Posted September 1, 2007 Is the GRP slightly porus? Link to comment Share on other sites More sharing options...
Vernon B Posted September 1, 2007 Author Share Posted September 1, 2007 Right Guys - Further to Jon's suggestion I've just come in from removing a section of interior panelling that runs across the front winscreen. Think of this as a pelmit between the winscreen and the section of the cab that contains the bed. There is no dampness or evidence of dampness behind this panel. In fact the dampness stops immediately at the top edge of the panelling - as if the pressure of the fixings prevents moisture travelling any lower down. In my opinion this shows that the moisture is moving down from above, not up from a poor winscreen seal. Worth doing - rules out another possibility. Jon's other observation is also a very good one - what if moisture is trapped in the cavities of the GRP moulding following the resealling of joints at the factory? This would be consistent with what I'm experiencing but those joints were resealed nearly 12 months ago. So here's my next question. Can anyone suggest away of drying out those cavities without undertaking a wholesale removal of the roof lining. From what I understand from the dealer (and they weren't absolutely clear) the GRP roof shell has a number of chambers or cavities. I was wondering if I could drill a pilot hole in the affected area and some how "draw" the moisture out by way of a length of plastic tubing - ??? Any thought? With ref to Clive's thoughts I pretty sure were not looking at porus GRP here. V Link to comment Share on other sites More sharing options...
Brambles Posted September 1, 2007 Share Posted September 1, 2007 Hi Again, Is this 'band' of damp were there is a cavity in the Glass Fibre structure of the roof to hold insulation, or indeed wood? If so it could be damp has got into the insulation or wood and not much wil be needed to change the thermal conductivity properties. Hence when the outside temperature drops this area cools inside quicker and you get the condensation from just 'normal' levels of humitity in the van. I see no reason why you cannot drill some very small pilot holes and probe with your damp meter. If there is damp inside then removal will be difficult unless the structure is porous to some extent to allow air to be pumped or sucked through. Probably best to cross that problem if established wether moisture exists in the cavity or not. What I do not know is how the roofs on A-classs are insulated in the structure. Fibreglass matting (easy to suck water out but may compress the matting) . solid insulation like polystyrene foam (unlikely as solvents in manufacturing glass fibre moulding would dissolve, some other type of foam (imagine moisture could be sucked out if it absorbed in there in the 1st place). Wooden parts are damp - these can be dried out by drilling pilot holes and I have seen somewhere pellet things you insert that soak up mositure and you keep replacing until moistuire level has fallen. Just ideas and hope it helps. Jon. Link to comment Share on other sites More sharing options...
Vernon B Posted September 1, 2007 Author Share Posted September 1, 2007 Hi Jon - thanks for that. I'm at a loss about the structure of this GRP shell and so is the dealer apparently. It might be that the insulation is simply an air void. One of my theories is that I'm only getting moisture readings in a particularly area because the manufacturer failed to add an insulation material in that spot - but I'm guessing. It would certainly be helpfull if anyone here had a knowledge of how these things are built. Anyone??? I doubt if it would be timber (weight/practicality) but hope it might be some form of fibre rather than nothing at all. V Link to comment Share on other sites More sharing options...
flicka Posted September 1, 2007 Share Posted September 1, 2007 Vernon No experience of this myself, but could it be a problem that it is an area where collects warm humid air, which then does not have anywhere to "fall" as it cools and therefore retaining all the damp air in the space. If so I would suspect that a number of "A" class M/H's could suffer from the same malady. If you check your when the bed is lowered and the bedding is not in contact with the roof lining for damp, IMHO it would indicate condensation being trapped in this area. Link to comment Share on other sites More sharing options...
Charlieme Posted September 2, 2007 Share Posted September 2, 2007 I dont like drilling holes but a vacuum cleaner could be used for suction. Perahps you already know............but Putting moisture absorbant material inside a cavity does'nt remove the moisture, it collects it, you then have to remove that material yourself and dry it before starting the process again. Just had another thought...........when the area is damp you said you use a heater it then becomes dry in a set amount of time. Where does 'that moisture' go to, if it disperses leaving you 'dry' and does not return for a set time then the moisture is not from the vehicle interior, for it would simply re-appear in the same place again. Sounds like its creeping in from elsewhere. A test.....when you are totally dry, boil a pint of water in a saucepan with the lid off and see if it progresses to your suspect area, this could prove some of us right or wrong. Link to comment Share on other sites More sharing options...
Old Git Posted September 2, 2007 Share Posted September 2, 2007 This will be the totally blind leading the partially sighted, but if it helps what is clearly a very tricky problem . . . . Is it water that is causing the meter reading? As I understand it they don't detect moisture, but variations in conductivity, and other substances might cause this I guess. When I had a caravan there appeared an area about the size of a dinner plate under a window which gradually developed into a rash. There were dozens of tiny sharp lumps appearing under the surface skin which were quite visible and the surface was very rough to the touch, but a moisture meter gave inconsistent readings, a bit like this problem. With the help of a caravan engineer I did all the right things, removing one variable at a time etc. but could never establish a consistent and repeatable pattern - though I'm sure there was one even if neither I nor he could isolate it. It lasted for several months, then slowly disappeared just as it had arrived, and eventually left no sign of ever having been there. After much head scratching and discussion with the engineer (who had become quite intrigued by the problem) he concluded that it might have been an area that had trapped some solvent or glue or similar substance during manufacture, which was slowly finding its way out. Its position under the window led to instant thoughts of water ingress of course, but he thought in the end that this was coincidental - and since I kept the caravan in identical conditions for a further five years with no recurrence or damp problems, I think he must have been right. This might be complete drivel in relation to this situation, but the daftest idea from one person sometimes triggers a solution in the mind of another - and I hope this might help. Regards - and good luck with the investigation. Dave Link to comment Share on other sites More sharing options...
Brambles Posted September 2, 2007 Share Posted September 2, 2007 I have a suggestion to try and track this down, might be daft. maybe not. Dry an affected area, then stick a piece of polythene over it sealed around the edges with sticky tape. Wait until moisture appears again, or sooner, and see if damp occurs under the polythene, would not have to be a large area..just a section of affected area. WHY? To see if damp is indeed passing through the GRP. GRP is not imperverous to water. I have also been reading up about GRP and if damp got in before the GRP had fully cured or had other problems then the initial leak could have affected it adversly and made it more porous. Anyway, assumming there is a pool of water in a cavity and possibly saturated some insulation then it could indeed slowly migrate through the resin. The polythene test might prove or disprove this idea. Jon. Edit - corrected some typos - this keyboard cannot spell as well as my last one! Link to comment Share on other sites More sharing options...
Charlieme Posted September 2, 2007 Share Posted September 2, 2007 And yet another suggestion When completely dry get the hose out and spray very lightly like rain the outside body in one area at a time, this could take some days but may lead to finding a moisture entry at the opposite end of the vehicle. The damp area of insulation material you describe may contain a chemical that readily absorbes moisture, as another member said perhaps there is a composition of chemicals in the lining that has not 'proved and set' correctly. Can you supply a picture of the offending area? Link to comment Share on other sites More sharing options...
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