I am interested in your opinions on gabrel roof problems. I have ben handed a project that requiresz the venting of this roof. It sweats terribly at pesent and is ruining the interior walls. The venting of the roof is a no brainer, but am wondering what the thoughts are on the shingle siding on the steep pith of roof/wall. This home sits with total exposure to the elements including 6 of 7 days sun here in the high plains of montana. I think the walls are getting super heated , and retaining this solar gain , while the evening cools and with zero venting are creating condensation probs. I am afraid that even with the upper roof vented that the walls will still sweat? I’ve never dealt with a gambrel roof before but my hunch is that a wood siding would better serve this home by releasing the heat build up better. A shoddy builder really did the home owner a diservice on this one. Not only is the roof unvented it is only a 2×6 roof and stuffed with r 38 and the framing leaves alot to be desired. Any thoughts on this t-lock shingle siding would help. thanks, Fup
Discussion Forum
Discussion Forum
Up Next
Video Shorts
Featured Story
Listeners write in about haunted pipes and building-science tomes, and they ask questions about roof venting and roof leaks.
Featured Video
Highlights
"I have learned so much thanks to the searchable articles on the FHB website. I can confidently say that I expect to be a life-long subscriber." - M.K.
Replies
Fub,
The shingles aren't black or really dark by any chance?
You may have to run a powered exhaust system in this attic if what you say is the cause. Is there not even a ridge vent?
Gabe
Yes the shingles are dark, red and green.No there is not a ridge vent. This was done by a fly by night "carpenter " around ten years ago. Every thing he touched has gone to#@$!. Without redoing the whole roof, the owner does not want to spend the $ , I am thinking of extending the upper roof tails to create a drip line that will clear the walls, as the windows are leaking too.In the new eave space I think that round vents in each rafter bay along with a ridge vent would create enough draw too vent this puppy. I am also thinking that it may help to vent the walls by drilling holes inthe top plate to let out moisture from the walls. This is gonna be a project where one will have to open her up and see what this guy did when first building it. What's your thought especially on the shingled walls. I would love to rip it all off and go with a nice cedar shiplap. It would add to the houses effect as it is at it's core an old log homestead on first level. To be honest I'm not sure I want to even tackle this one without some clear realizations from my friend/ owner that we are gonna have to feel our way through this on .... Thanks Fup
The one question I haven't seen asked nor answered is where is the water coming from?Andy Engel, Forum moderator
Fub,
To even come close to this one is a guess at best.
IF the house is a/c'd and there was NO insulation whatsoever at the intersect over the windows, NO vb and not sealed, I could almost imagine moisture droplets forming over the top of the window headers.
Has anyone checked the humidity level in this house?
Gabe
R-38 in a five inch space is really only about R-11 and probably not that since it is wet and maybe moldy. I'm thinking gut and re-doo from inside with sleepers to increase space and vapour bar before new Sheet rock. Maybe foam too but how much interior space can they afford to lose? It could be a cold roof on the outside, your cedar siding idea would make it a rainwall, sort of.
Gabe, where is fred on this one? LOL Good example of how his theories on dense pack with no vent is unacceptable.
Andy has the most important point - control the moisture at the source so it doesn't find its way into the wall/ceiling.
Excellence is its own reward!
Piffin,
I don't discount anything on this one. There has to be more than the lack of ventilation theory.
Would be nice to have pictures of the damage.
Gabe
Lack of decent ventilation
Lack of proper insulation
Lack of sufficient framing
Lack of vapour barrier sealing
and possibly abuse of the envelope
right?Excellence is its own reward!
Maybe.
Maybe he has a hydroponic grass growing operation in the basement.
Maybe the dryer vents into the house envelope.
Maybe he has a running stream under his slab.
Maybe.........
Gabe
That's what I meant by abuse of the envelope...Excellence is its own reward!
If you've got a good crop, how's that abuse?
Gabe
Piffin, I don't think you can discount un-vented dense-pack based on this example, which doesn't use dense-pack cellulose. I suspect that there are a whole bunch of things done wrong in this house. Do a web search on the Build America program, and you'll find plenty of examples of succesful unvented roofs.
Variables, there's lots of variables. I can point to vented roofs that ice dam every winter, and unvented roofs that don't. And vice versa. I think that either approach can work, if it considers the whole house and not just one factor.
In that particular case, I'm surprised that there's any problem because I think of Montana as a pretty dry place.Andy Engel, Forum moderator
It is dry, but like in the mtns of Colorado, the nights are EXTREMELY cold which increases the contrast and amy of condensation. Lots of occupants also add plenty of humidifiers to keep from having dry nasal tissues which cause spontaneous bloody noses too. That added interior humidity incontrast to below zero temps outside increases the need for a vapour bar and ventilated spaces. I've lost count of the number of calls I had out there for roof leaks that truned out to be condensation - especially on north sides and above baths and kitchens, the sources of moiosture.
You've got to absolutely 100% stop the moisture from geting into the attic space or ventilate it regardless of your insulation plan. I agree you look at the whole package and this house is lacking lots.
Excellence is its own reward!
Thank you all, yeah this house is a mess. The nbuilder really screwed this lady over! No vapor barrior, no vents etc. on the gamrel there is no attic space, just sheetrock to the rafters and plywood !/2 in. with insul stuffed between How about framing the upper roof with 2x10, and leave space above insul for vent out the soffit?replacing the sheetrock is gonna be manditory, so vapr at that juncture. Would holes at top plate of wall allow moisture to escape out the soffit vent? Just an Idea. There are cheap bubble skylights that Id like to replace with some nice velux windows, never had a problem with them leaking and may hold in a bit more heat than thos cheapies. There are windows on the walls place to framing with no dormer, so moisture goes down the shingled wall and finds it's way into the home as well, can you say start over! Fup
Let's get serious for a bit.
IF the occupants have a normal lifestyle and there is as much condensation occuring as you say, the first thing that would come to mind would be a total envelope failure.
You would have to work it from the inside.
Remove all drywall on the exterior walls, strip and clean all insulation.
Skip the ventilation theory.
Use pu foam and seal that sucker all round, including behind the plugs and every crack nook and cranny. The next day paint the foam.
Install a good bathroom exhaust fan and kitchen exhaust not a recycling filter type.
Cover with drywall and finish.
If that doesn't work, back to my hydroponics theory and the grass crop.
Gabe
I'm on board with that idea!Excellence is its own reward!
Piffin,
If you want to come aboard, you will have to bring a fishing rod.
:) Gabe
Gabe, this is scary. We agree on something. Andy Engel, Forum moderator
You must mean about the fishing rod?
Gabe
Maybe that too. Andy Engel, Forum moderator
And here it was that I thought you were mad at me for not leaving with the rest........
Gabe
If you look at my website which is the house I built http://www.cliffordrenovations.com you'll see the two gambrels I slaved away over. Been here now almost five years and havent had any problems and I have dark asphalt architecuals over it. My suggestion would be to see if theres at least an inch of air space between the roof sheathing and the insul. If not ya gotta do whatcha gotta do. Easiset of all the two solutions is rip the interior rock. and then the insul. Install foam baffles to the sheathing to a ridge vent and soffet vent. I know I know easier said then done but without that air space the homeowners are doomed.
Be well
Namaste'
Andy
It's not who's right, it's who's left ~ http://CLIFFORDRENOVATIONS.COM