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Question DetailsAsked on 1/11/2018

The ceiling tapes are sagging. No obvious leaking point is found. Why does it happen?

Our ceiling tapes are sagging, which started two weeks ago. It happens at multiple place in our living room (vaulted ceiling) and our kitchen (has an attic). We have open kitchen to the living room. We called several roof companies, and they give us different answers. No obvious leaking point was found. One company think it's roof vent related, and suggest us to change all the vents. Since they see mold in attic but no discolor to indicate the leaking. Another company think it's bad nails under the shingles, and suggest us to install hundreds flash cards over the whole roof. Totally confused and don't know what we should go with.

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I would guess you have paper tape rather than fiberglass mesh tape on your drywall joints - that generally peels loose a lot better, both because it absorbs moisture, because it has a pretty smooth and non-porous surface so it does not bond well, and because there is very little push-through of the drywall joint compound in application, so it acts more like a "tape" which can peel off, rather than as an embedded "reinforcing mesh" like the fiberglass does. Course, paper tape can make getting the joint smooth and finished easier because of its smooth surface, so many drywall tapers still use it even in new homes for speed - can eliminate a couple of taping drywall passes - though I personally recommend fiberglass tape for ceilings because of the peeling thing.

It would take an eyes-on inspection to tie the cause of this down, and evidently you have run into the problem of several contractors saying different things, so you are rightly confused. Many (most ?) roofers are not really trained at all in attic moisture issues, so you commonly get conflicting an sometimes dead wrong recommendations like spraying the underside of the roof with foam for instance.

First - the peeling. There are two normal causes for this - putting on the joint tape without first layering on a layer of joint compound for ti to embed in, so the tape is only very marginally bonded to the drywall at its edges and maybe (if perforated, which some cheap ones are not) by tiny spikes of joint compound through the perforations. The other, far more common cause, is moisture getting to the tape and dampening it - sometimes from the inside against a cold ceiling (especially with cathedral or vaulted ceilings) but in that case almost always if the interior surface moisture was high enough to cause tape peeling then you would have moldew/mold starting to form on the ceiling itself unless it is very cold - generally starting at the edges against exterior walls, or the highest points in peaked/cathedral/vaulted ceilings.

But, if you are in the recent cold spell, this could be the cause - in which case (if still that cold) running the back of your hand over the ceiling in that area would likely give you a "damp" feeling -maybe not free water on the surface, but a damp feeling, and the joint compound might feel soft even through the paint. (BTW - normal house ceilings are sprayed with a flat paint and commonly only one coat andmany times no primer, so the paint is not a good barrier against moisture transmission.)

If you have lived in this house for quite awhile and this is a new thing, and occurring at several locations as your say, not just one place, if you have been enjoying the recent "chilly" weather, it could well be this is largely an isolated case of the extreme cold causing condensation on the underside of the ceiling or in the attic, wetting the tape enough to make it peel - which would be indicative of a moisture "problem", but may or may not be one that would be considered a long-term or permanent issue which needs more than a joint repair (with fiberglass tape). This tape peeling might or might not be related to the mold in the attic - I have seen a lot of attics with might mildew or mold with zero structural or ceiling damage - especially in areas where it goes from near-freezing to very cold conditions in just a day or two as fronts move through, causing condensation and frosting of the attic moisture during that time, which then thaws out when it warms up and forms light mildew/mold.

Would also commonly have visible condensation on the underside ofthe ceiling in the coldest outdoor weather if the ceiling getting cold and condensing interior moisture was the problem. If you have been having record or near record cold conditions recently, this is quite likely a good portion of the issue - ceiling condensation as the cold attic pulls the ceiling inside temperature down below the dew point at the cold drywall, causing condensation - same reason moisture condenses on colder bathroom mirrors and windows in cold weather. Again, can happen in any ceiling but higher up in peaked or two-story high ceilings is more common - both because the moist warm air rises up there and then cools at the surfacde, generally combined with poor circulation to remove the now higher humidity air up there so the humidity rises as the air cools, creating a little cool, damp microclime. I have even seen, in a couple of rare severe cases in true winter areas, fog forming in a high, poorly insulated peaked ceiling with very cold attic above it, and in a couple of cases frost formation on the underside of the ceiling. This is where ceiling fans reversed in the winter to circulate warmer air up there come into play in many cases.

Lacking indications of that, moisture is most likely coming through from above - the mold in the attic would tend to indicate that could be the cause, or at least a portion of the source of the moisture. Getting in the attic (remember to step only on framing not on the top of the ceiling drywall) at a point over the worst peeling tape and pulling back the insulation would probably reveal moisture in the attic insulation if that is the source - either from a leak (which should be a distinct wet and/or moldy spot in the insulation if from a specific point roof leak or leaking roof penetration duct), or from general wetness in the attic.

General wetness would normally be from condensation and/or frosting in the attic due to excessive moisture leakage from the house into the attic (through ceiling and wall penetrations and/or incomplete vapor barrier right above the ceiling drywall) combined with inadequate attic venting to remove it, or excess moisture coming into the attic from leakage or venting directly form the house through vents. For instance, kitchen and/or bathroom (latter is most common) vents emptying directly into the attic rather than venting outdoors is a very common cause of this - sometimes (against code) intentionally done that way by the contractor just to save the time and money of doing the roof penetration, sometimes because the ducting was stubbed up but not correctly tied into by the roofer when the roofing went on if that was done after the fans and exhaust ducts were installed.

On the nail issue: yeah, those hundreds of cards (patch pieces ?) over the roof would look real good even if they worked - and come resale time would pretty much guarantee to scare most buyers away, and the buyers not scared off would probably have a contingency item requiring total roofing replacement for the deal to go through. I would stay away from that guy - because "cards" would not be very waterproof, being just a "patch" on the roof - sort of like slapping duct tape over something to make it temporarily "waterproof" Even if "glued" down with asphaltic mastic, I would also expect to be seeing some of those peeling off in not manny years - defeating the purpose. Assuming he meant cards of shingle material or ice and water shield or water barrier or such, even if they stuck down well and sealed, exposed to the sun without a covering stone chip layer (like shingles have for that purpose) to protect from ultraviolet weathering those would not last well anyway. That strikes me as a Rube Goldberg approach for a shingle roof. It is done for repairs on flat built-up (layered tar and tarpaper) flat roofs using the built-up method to imbed a multi-layer patch, which might be where he got the idea, but not here - if done that way would be glaring black patches all over.

If one wanted to waterproof the nails I would either cover them with asphaltic mastic (which has limited life so would need redoing every 5-15 years) applied with putty knife as a sealant over the top with sand scattered on top and embedded to protect the tar from weathering (which cracks it), or carefully (if shingles are not so old they crack in the process) pulling the nails one by one using a properly shaped slotted prybar slipped in under the shingle and pried up to get the nail head up high enough to remove with a prybar or diagonal cutters without breaking the shingles (like you do to replace a broken shingles strip), then asphaltic mastic injecting the holes with a caulk gun to fill the hole through the shingles and the water barrier which has been leaking, then renailing with next larger size stainless steel roofing nails (larger so they fit tight in the existing hole). Technically one would renail at the "correct" location, which is several inches up under the overluying row tabs - but bending back those tabs to nail in under them like that is likely to cause a lot of cracked and broken tabs on all but a fairly new roof. VERY labor intensive too. But personally, I doubt, unless maybe if the nails were also too short so they are "jacking" or working up in the holes, that you would get much water into the attic from them anyway - most of it should be stopped at the water barrier membrane under the shingles and run down the roof under the shingles on top of the membrane, dripping out under the shingles at the eaves. Anything which got through the waer barrier would then have to get around the nail through the sheathing, which would swell up around it when wet, making for a pretty tight place to wick through. For instance, shed roofs with roll roofing (which is basically just roll shingle material) are nailed right through the exposed roofing material along the edges, and if done right do not leak appreciably, so I really do not think the nails are the issue, or at least not the primary issue here. (The above refers to asphalt "composition" shingles, not wood ones - taking them up to renail in the right spot is pretty much a lost cause because so many will break in the process.)

If the nails are exposed on the roof - i.e. not in under the leading edge of the next uphill row of shingles, then even if that were the cause of the problem, I would be expecting to see a blackening around the leaking nails, and probably general brownish and/or haloed staining on the underside of the sheathing (the plywood or tongue and groove which the shingles are nailed through). If bad enough to cause drywall tape peeling, then I would be expecting a pretty general staining on the sheathing and a lot of black streaking downhill from at leaat some of the nails. Also, if the wetness is from actual roof leakage, generally you would have specific spots of significant wetting, and if enough to cause drywall tape peeling would probably also be causing attic insulation matting and staining and drywall ceiling staining in the same areas as the water starts leaking through the drywall. Or water pooling in the attic, especially if you have plastic vapor barrier on top of the drywall as most house since about the 60's/70's have, which then runs out at seams in the vapor barrier which are not watertight or to openings in the ceiling drywall so stains around light fixtures and any other ceiling penetrations like fire alarms.

Of course, how old your roof is also affects the decision if it looks like the nails are contributing to or causing the issue - if it is nearing its normal life (commonly 20-30 years with most asphalt or untreated wood shingles, 30-50 years with long-life heavy duty asphalt or treated wood shingles)

You can find a LOT of other previous questions with answers in the Home > Roofing and Home > Insulation links under Browse Projects, at lower left.

A bit of detecting might revea lthe cause of this. For instance, if the mold is predominately or totally on the underside of the sheathing, and especially if the sheathing is soaking wet (not just surface damp) or "punky" then wetting of the sheathing due to leakage from above would be the primary suspect - so a reroof job would normally be the cheapest solution because if the nailing is the problem then pulling and sealing every nail and resetting it in the correct placerequires essentially a shingle-by-shingles tearoff and replacement - so a total tearoff and reshingle (with new water barrier underneath too) would almost certainly be the cheaper solution. Plus incremental removal and renailing will result in some damaged shingles - so the replacements, even if concentrated in one place rather than scattered around the roof, might make for a roof appearance which would be opjectionable and/or inhibit resale.

If the attic framing and sheathing both have mold or mildew on them, but the insulation on the attic "floor" does not have matting or mold or staining or wetness from actual saturation, then condensation/frosting on the underside of the roof in cold weather would be my first guess as to the cause - with generally high attic moisture due to inadequate ventilation.

If the insulation is locally matted or mold-spotted, especially if under specific spots like roof pipe or duct penetrations, or in dalmation spots under specific nails, then dripping from the penetrations or nails (which can also provide the moisture to also cause mildew/mold on the framing and underside of the sheathing) would be suspected. Ditto if there is staining or actual wetness on the framing below the insulation fill line or under the insulation - on top of the drywall ceiling or overlying vapor barrier between it and the attic floor joists or lower chords of trusses.


Certainly the peeling tape needs to be pulled back and redone - but not much sense doing that till the proximate cause if fixed.

With the mold in the attic, if more than just possibly a few spots where there might be specific leakage, excessive attic moisture would be the primary suspect. You talked about attic "vents" - the attic (unless totally within the "conditioned space" so heated and air conditioned with the rest of the house) should be well vented. Flat roofs are a special case and commonly use rooftop mechanical or fan-powered ventilators to keep up the air changes in the "attic.

Typically, with normal peaked roofs as you presumably have, since you have shingles, eave venting (including a greater area of corresponding ventilation through any soffit covers under the eave overhang) allows inlet air into the attic to provide ventilation air circulation. With peaked roofs the normal and "best" solution, and except in rare "trapped air" cases with odd-shaped roofs much better than roof "mushroom vents" or such, is to provide ridge venting (special types are available for heavy blowing rain and snow areas to prevent blow-in to the attic) along the ridges, which lie over a slot cut in the sheathing to provide for airflow at teh peak and ridges of the roof.

Lots of discusssions can be found in the Home > Roofing link under Browse Projects (at lower left) about condensation or frosting in the attic in very cold weather if you have a lot of gaps in the vapor barrier letting air in from the house - so properly (using rock wool or fireproof furnace duct contact rated sealant around any "hot" flues like chimneys and furnace flues) sealing at least around duct and pipe penetrations from the house as part of the job can help cut off that source, as can properly sealing around ceiling light boxes and fixtures - replacing vented "can" type roof lights with types which are airtight to prevent household air penetration into the attic. (BEwreon airtight cans about what bulb you use - many cannot handle incandescent light and require special "Type R" or LED/CFL bulbs to avoid overheating). A complete job includes pulling back the insulation and sealing ALL penetrations and openings, including proper taping of joints in the vapor barrier (hopefully there is one there), sealing around wire and pipe penetrations through ceiling and tops of walls, etc.

One thing I did not mention - though this would usually result in a spot leak in the ceiling - if you have any water pipes in the attic for water heater or such, check for possible leaks contributing moisture.

Who you go to for the "answer" is a tough call - because a roofer is likely to say new roof is the solution, an HVAC contractor is likely to say mechanical lroof vents, an insulation contractor likely to say more insulation, etc. For an independent opinion, and to evaluate whether the mold has led to rot requiring some structural repairsor sheathing replacement too, I would say you now need an independent architect or engineer with a lot of remedial house repair design experience (not just a designer, many of whom have rarely set foot in a real attic) or perhaps a very experienced "old school" Home Inspector, to peck around in the attic and check for wetness and where the mold is and such using a moisture meter and BRIGHT light.

Oh - on the mold in the attic once the moisture source is remedied - if a light fuzzy coating which rubs off easy (not deeply stained into the wood), sometimes just a mildewcide spraying to kill it, ideally combined with a borate solution to inhibit future similar molding/mildewing, can usually take care of it. If heavy, then commonly full removal of the insulation if also mildew/mold impregnated (commonly is if there is a lot of attic mold), a physical and chemical (kill and brush/vacuum) removal process is done on the framing and sheathing, followed by any repair needed to any rotted spots in the sheathing or framing, then followed by spraying with mildewcide (boric acid base or other chemicals), and finally sealing openings into the attic and insulation replacement. Mold Detection and Remediation is the Search the List category for the mold removal and treatment, though any actual framing repair needed would be a Carpenter - Framing or Roofing company's type of work. If a bad case, where serious remediation of the attic is needed including mold removal, repairs, insualtion replacement, treatment, etc usually yuou would get a general contractor on board to handle the entire thing under one contractor, using subs for the specialty work.

Any work requiring replacement / repair of framing will almost certainly require an architect ro engineer's remedial design to be able to get a building permit and for the contractor to work to - so having an architect/structural engineer do the inspection and develop the solution is the first step toward that.

Note if insulation is taken up for mold remediation reasons, I STRONGLY recommend that sealing penetrations allowing airflow from below be done before mildewcide spraying and new insulation is put in - both because that will eliminate moisture which may have been causing or at least contributing to the problem, and also because new insulation would likely be done to current standards (so about twice to three times as thick as previous) for energy conservation code compliance, which can unfortunatelyk more readily trap moisture in it, potentially causing new moisture problems in the insulation and bottom parts of the framing because of the restriction and colder temperature at the top of the insulation, which can cause condensation and frosting in the insulation itself if it is thick. This sort of moisture trapping is more common with blown-in cellulose or natural fiber insulation than with fiberglass - which not only does not absorb moisture as readily but also does not support milkdew/mold nearly as readily.

I emphatically recommend AGAINST foil barriers in attics - generally (in my opinion) they do not work in the long run as dust accumulates on them, can commonly trap moisture, and are commonly grossly falsely advertised and even if the claims are true, are usually grossly overpriced for what they promise to deliver. It is a developing technology that is FAR from being ready for general residential use, and many of the applications and products actually violate good thermodynamic and moisture-control principles and aggravate attic issues, causing new problems which can be very serious in some cases. Good airflow (through an unheated attic) is by far the better and safer solution.

Good Luck - and remember solving this might be an incremental thing - like solve moisture buildup issues (better interior ceiling or attic ventilation with ridge venting for instance as a first step), then see if that solves the issue before taking more extensive steps. It is also possible (though mold in the attic does call for some ventilation or moisutre control there) that this was related to the extreme cold, and redoing the joint taping with fiberglass tape and water-resistant taping compound. Not available everywhere, but is at many lumberyards and probably all drywall and plaster wholesale supply houses. Might be enough to solve the peeling issue. Commonly sold as "moisture and mold resistant joint compound", advertised usually for use on bathroom walls and ceilings.

Answered 10 months ago by LCD

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