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Question DetailsAsked on 3/13/2017

Water leak from second floor bath to first floor ceiling through light fixture

we had a accidental water leak at the master bath at second floor and it started dripping down to the living room in the first floor through the ceiling light fixture. We immediately stopped the leak and dried the master bath. The leak through the ceiling light fixture stopped shortly after that. I called up my insurance company and informed about the leak too. The contractor may arrive within a day or two. Meanwhile, I'm wondering what precautionary steps that needs to be taken. I don't have much experience as a homeowner and thus little worried about the damage. The leak stopped completely but I do see some water patch around the lights and in some other spots on the ceiling. I'm little worried that water may have clogged in the ceiling and may lead to mold formation and could possibly weaken the ceiling. How are these conditions repaired in general? How much it usually costs to fix? Appreciate your valuable inputs.

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2 Answers


I would tape off the switch for that fixture till the ceiling area is dried out - ditto to any other lights or fans mounted in that same ceiling, just in case they are wet and might short out.

Assuming your ceiling is visually flat, or the low point is at that light fixture (likely, since it leaked out there), the chances of a lot of water weight being up there is pretty small. Usually, living room light fixtures include one pretty much in the center of the ceiling, which is normally near or at the center of the supporting joist spans so is also the low point due to natural joist sag, so usually the water drains out at the center light fixture opening and doesnot build up significantly elsewhere on the ceiling drywall or plaster.

If you have any other visible low spots, to be on the safe side you could take a screwdriver (normal size phillps head one works well for this) and poke it though the drywall or plaster in any noticeable low spot(s) in the ceiling (not at a tape joint, if you can tell where they are, to avoid joists) to provide a drain point - having a bucket ready of course to catch the maybe up to a gallon or so of water which might be in there. To avoid hitting joists, you can start with a finish nail driven through the drywall to make sure you are hitting an open spot before punching a 1/4" hole with the screwdriver. Remember, this is only if you have other noticeable low spots - which will typically show up within 4 hours or so of the leak as water-stained spots or drips.

Now- until a Water and Smoke remediation contractor gets there - the more you can dry it out the better. In the bathroom run the ceiling fan for several hours at a time (not continuously - they are not necessarily rated for that), and preferably (beware of pet or child risks) running a large (like 20-24") fan so it blows air into the room forcefully across the floor from the open doorway will dry out the flooring, commonly without visible damage unless a wood-based laminate or plank. Sometimes vinyl/linoleum will peel or buckle, depending on how much the water got in under it. Tile usually does not get damaged unless the water stayed there for a long time and started seriously swelling the subfloor underlayment (plywood or OSB or particle board or such). Of course, the better the construction methods used, the less likelihood of damage - i.e. marine plywood behaves better than Interior/Exterior which bahaves better than OSB or particle board.

The ceiling I would not worry too much about - just make sure the house humidity is kept low - which might mean (depending on household humidity and outdoors conditions) letting some lower humidity outside air into the house from time to time by setting up cross-ventilation between windows. If not in heating season in your area, additional A/C operation can help remove the moisture from the house - as of course will turning off any humidifier for a few days, be it on A/C or furnace. A fan aimed at the ceiling light area could help reduce moisture in the drywall.

OF course, pay attention to safety - if you have to be out of the house at times, personally I would not leave the fans running unattended - especially if there are pets roaming the house.

Usually, a short-term one-time wetting like this does not cause damage to the framing - just water stains it, but usually the water evaporates well enough just through the wood and drywall to the household air to prevent noticeable mold or mildew growth as long as the surrounding environment is kept reasonably low humidity and airflow is keep high. Then after the contractor uses fans and forced-air flex ducting into the subfloor to dry out the subfloor area and the top surface of the drywall, remediation is completed by painting the affected areas with Kilz or similar mildewcide and stain-blocking paint, followed by repainting (usually the entire affected wall(s) and ceiling(s) to get a match, with finish paint in the desired color.

Bathroom flooring - depends on amount of wetting and type fo flooring whether it needs replacing or not.

In rare cases, usually only if there was enough water weight to crack or collapse the ceiling (rare that it builds up that much before leaking out), or if the drywall is some of the high-sulfur stuff from the Southeast a decade or so ago so it forms corrosive sulfuric acid, then the drywall needs to be replaced. And if the drywall happened to be the corrosive type, sometimes any wiring or metal piping up there has to be replaced too, because some of that stuff is NASTY - corrodes metal nearby within just a day or so when wet. (Note - in very old homes the same thing happens in some houses built before the 70's, when nsome very high-sulfur drywall and plaster got into the system - mostly in the Pacific Southwest because it came out of a plant in Arizona or southeast California, as I recall. Actually turned a pretty birght orange when it got wet, and was corrosive enough it rashed and damaged skin while working around it when wet or sweaty - I remember having a "sunburn" around the neck for weeks one time because of drywall dust going into the shirt collar.

If water got into regular light fixtures the bulbs are removed and they are usually blown and aired out till thoroughly dry, then tested for operation. If low-voltage fixtures and the transformers got wet, those should be replaced - ditto to transformer-on-bulb or transformer-on-socket lamps. If LED or CFL or Halogen bulbs got wet, some contractors will dry them out well then try them - others like me do not trust them if water ran over them and will replace them because a damaged CFL or LED or Halogen bulb can do some nasty things when it shorts out, including throwing off glass and molten ceramic and plastic sparks.

Ditto if a ceiling-mounted fan unit got wet inside - at a minimum it should be THOROUGHLY dried with a fan, then tested. Personally, I would not retain a fan where the motor or interior wiring/transformer got wet - some drips off the light arms only I would dry and test and replace any wetted non-incandescent bulbs. (Regular incandescent bulbs are pretty water tight so they are not normally hurt by a bit of water running over them).

Answered 3 years ago by LCD


Answered 1 year ago by qwe

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