Question: I made a big mistake, after finishing our basement, with not hooking up the bathroom ceiling fan. Now we have rust on most of the metal ceiling grids. Short of replacing all the grids, is there anything than can be applied to them that would remove the rust? K. Phillips.
Answer: Identifying the exact cause of an issue that has caused damage or deterioration to a component in your basement is your first step to remediation. Unfortunately, replacement of the rusted T-bars in your suspended ceiling may be the only way to permanently prevent further corrosion and deterioration.
It is unusual to get an inquiry like yours, where the solution to the problem has already been identified, and likely remediated. I have seen this issue many times in basement bathrooms which have been improperly or inadequately ventilated. Most often it is caused by the lack of a working exhaust fan, but as in your case, it is sometimes due to an improper, damaged or disconnected duct coming from the fan. The results of this can often be more concentrated than with missing ventilation, as the moist air drawn from the bathroom fan is dumped into a smaller area. In your home, the small cavity above the ceiling would get the brunt of this moisture, making quick evaporation impossible.
From your submission it is not clear whether the rusting suspended ceiling bars are limited to the bathroom ceiling, or the entire basement. The approach to dealing with this may be different depending on which scenario is seen in your home. Firstly, if the rusty T-bars are only seen in the bathroom, then the solution should be quite straightforward. Since that is a small area, it should not be that costly to remove the ceiling entirely and discard or recycle the rusty metal components. I would suggest looking for replacement components made of aluminum, instead of steel, to prevent a reoccurrence of the corrosion. That is a strong possibility even with a properly vented exhaust fan, but may occur at a much slower rate. I would recommend contacting a commercial supplier of drywall and ceiling products, if not available at a retail home centre. Once reinstallation is complete, the original ceiling tiles may be reused, if not damaged.
If the moisture issue is more extensive, causing most or all of the metal bars in the basement ceiling to rust, replacement will be more costly. The extent of the corrosion will likely determine how involved the repairs need to be. If only a portion of the ceiling T-bars are moderately or badly rusted, especially if it is limited to the hidden portion above the tiles, then complete replacement may not be warranted. If there is only a small amount of rust on the unpainted upper steel sections, then they may be fixable. They may never corrode enough to be a structural or esthetic concern, now that the source of moisture is gone. Tiny amounts of surface rust on the hidden portion of the metal bars may be removed with steel wool, sandpaper, or a grinder. If that works, coating the cleaned bars with rust-resistant paint may nip the problem right in the bud. There are several brands of spray paint in cans, available at any paint supply, hardware store or home centre, which claim to prevent rust reoccurrence. They are very easy to use, but care must be taken to cover the already painted portions of the T-bars, to prevent overspray from the new paint.
If the corrosion is visible on the painted bottom portion of the grid, then there may be no other option than to take down and replace these members. If the rust is extensive enough to have penetrated the paint on these metal bars, it may be too late to prevent further progression. Also, that amount of rust would certainly have stained the ceiling tiles, which could also be affected by the moisture. While the metal ceiling grids have rusted due to condensation from warm, saturated air from the basement shower, the tiles may be affected in other ways.
Most suspended ceiling tiles are made from some form of compressed wood fibre, which may be highly absorptive. If they are subjected to high humidity conditions, over a long time, they will probably warp. In worse cases, brown water stains can occur on the painted surface, which may be hard to cover up, even with good paint and primer. Also, the rust from the sweating metal T-bars may have permanently stained the tiles, making reuse difficult. Again, if there are a limited number of damaged tiles, replacement will be the easiest solution. If the entire ceiling is in bad shape, then sealing and painting the visible side of all the tiles after removal may be an option, but will still be quite labour intensive.
Knowing that the corrosion on your basement suspended ceiling bars, and possible damage to the tiles, is caused by excessive condensation from a missing bathroom exhaust fan will allow the issue to be immediately stopped. Unfortunately, if the rust damage to the T-bars is extensive, the only solution is removal and replacement with new building materials.
Ari Marantz is the owner of Trained Eye Home Inspection Ltd. and the past president of the Canadian Association of Home & Property Inspectors — Manitoba (cahpi.mb.ca). Questions can be emailed to the address below. Ari can be reached at 204-291-5358 or check out his website at trainedeye.ca.