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Question DetailsAsked on 2/2/2018

who do i call first for water stain on celing. Right below the attic. Appears to be in center of house pitch maybe

went up in attic and rafters appear wet. We have a roofer coming tomorrow but want to be sure it might not be something else. Will they know if it is something else or just try and sell us a new roof or vent cover.

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From the posting date looks like I might not have gotten to this answer before your roofer came, so issue may be solved by now. But anyway, in case not resolved or in decision status still here are my two cents worth.

Since you can get into the attic, check out these possible sources:

1) look on underside of roof - if a single wet spot then you have a roof leak at or uphill of that spot - an external check for leaking flashing or missing roofing would be needed

2) like above - if coming from or immediately downhill of a roof penetration like a vent, an on-the-roof check for leakage around the boot or seal around the pentration would be in order

3) if leaking around / through a bathroom or kitchen fan, two common causes for that - a leaking roof vent (or missing cap on one), or

4) interior air passing through a ventilation fan and condensing/frosting up either inside the cold roof vent, or in the ducting - or if the duct is not tightly connected to the roof vent, escaping and frosting up in the attic on the underside of the roof and on the framing. When it thaws out, it can then run down around or inside the ducting and come out at/right next to the fan unit. If this is the cause, commonly (when still quite cold in attic) has a burst of wetness coming down in the first minute or less after the fan is turned on, as the warm air passing through it melts the frost/ice.

5) of course, if leaking right at/adjacent to a water pipe or A/C drain or water heater in the attic, could be from that - though sometimes such a leak can run non top of the vapor barrier wuite a way, so in that case requires tracking the wet insulation back from the ceiling leak point.

6) you said "appears to be in center of house pitch maybe" - the pitch is the measure of the angle or slope of the roof - like a 4:12 pitch, so I presume you instead meant the ridge, not the pitch. If coming from centerline of a ridge with ridge vent installed, could be from blown-in rain or snow - rain can blow/splash in during driven rain events, and snow can blow in if not a ridge vent type specifically designed to prevent that (and even then can occur to a lesser amount with very fine, dry "powder" snow). Snow can then sit on the insulation till it melts. If it melts faster than warming conditions can evaporate it and the insulation does not retain the meltwater, can then wet the ceiling below. Look for a stripe of snow under ridge vent, ridge vent packed with snow and melting out and dripping, or wet stripe on insulation right under the ridge vent.

7) if no visible source in the attic, check the attic insulation at the ceiling leak point - then follow the wetness back to its source by tracking the wet insulation - bright flashlight is helpful for seeing where it is wet if fiberglass - cellulose usually easy to track by matting and drker color of wet insulation. Might be dripping from right above the ceiling leak point, or might be running on top of the vapor barrier (which is usually between the ceiling drywall and the bottom of the attic trusses or joists) from another source point further away.

8) rarely, if you have a lot of moisture coming into the attic from the house through unsealed ceiling penetrations and fans and lights, utility pipe/cable penetrations, lack of vapor barrier, fanducts not connected to an exterior vent hood, etc the attic can, in very cold conditions, build up quite a large amount of frost as the water vapor condenses on framing and the underside of the sheathing. In very cold areas I have seen commonly an inch or so of frost and as much as about five FEET of heavy frost buildup in attics (enough to cause ceiling drywall failure in a number of cases and even framing structural failure in a few cases) - if this melts quickly due to a rapid warming event, can saturate attic insulation and cause staining/drips on underlying ceiling, commonly running alone top of drywall or vapor barrier and then coming through at the center of the room (low point on the framing/ceiling) or through near-center light fixture penetrations.

If ALL your rafters look wet, that could well be from heavy condensation or frost buildup if you had a recent cold spell - which might or might not be the cause of your issue, might just be coincidental that you saw it and that occurs every cold snap (which would be indicative you have excess interior moisture coming into the attic). A slight dampness 9not soaking wet) is NOT necessarily indicative of a real problem if you had a rapid major drop in outside temps, which could have caused the natural outside moisture in the air to condense or frost up in the attic (as a frost haze, not in thickness) which can then dampen the sheathing/framing as it melts off when conditions warm up. Commonly this appears as frost/dampness only on the exposed framing, not the underside of the sheathing, because the rising warmer air and daytime heating from above can makes the sheathing too warm to cause the condensation/frosting - it can occur only on the exposed rafters and framing/trusses as warmed moist air blows through the attic, condensing on the colder wood framing. Common on sunny side of houses, where outside air is warmed as it rises along a sun-exposed exterior wall (commonly south or west side) so has high moisture level from melting/evaporating snow on the ground, but when it gets into the shaded attic hits the colder framing.

9) when you said center of house pitch, if you meant at/near a penetration or a valley, especially if you have had recent warming (or even intense sunshine in daytimes) or rain on snow, you might have water backup in snowpack or behind glaciering or an ice dam on the roof. That usually occurs within 3-6 feet of the lower edge of the roof, and almost always (unless you have eave thaw cables) is associated with significant icicling/ice damming at the edge of the roof.

But - if the eaves have melted back, sometimes that leave an exposed snowpack further up on the roof, which then freezes at the lowwer edge during the night and forms a snow/ice dam at that point midway up the roof, which can then cause backup of water under the shingles and leaking through the roofing to the attic. This also happens if someone rakes or melts the snow off the lower edge of the roof only, and sometimes with solar heating of the eave area and underlying wall, leaving the higher snowpack in place so the normal freezeup of meltwater and rainwater freezes mid-slope instead of icicling up at the lower edge as it usually would. This can be bad because in almost all roofs the ice and water shield installed to prevent leakage from ice damming is only on the lower 3-6 feet of the roof slope, so a mid-roof backup can get in under the shingles above the area protected by the ice and water shield.

Good Luck - and bear in mind that unless you have generally deteriorated / damaged roofing (or it is all coming loose in the case of tile roof, because of crumbling mortar) a total reroof is generally NOT called for.

Answered 2 years ago by LCD

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