Q: The front porch and garage of the 1912 house I co-own have been rebuilt to accommodate two cars. When it rains, there is a leak in the part of the garage that was added. Also, when we recently had the front of the house washed we noticed a leak along the line where the porch meets the house. Is there a sealant you can recommend that will stop this in the short term? I know this is not likely a long-term solution.
A: Your remark about a sealant being a short-term fix is correct. We would be willing to bet that down the road you’re going to need some new flashing.
But for now, welcome to the world of caulk. Walk into Home Depot or Lowe’s, and we guarantee you’ll be befuddled by the selection.
We’ve always used an acrylic-latex-silicone-blend caulk. As the name implies, it is a hybrid. It’s easy to apply and has proven to be durable. The ones we’ve used can be painted, so they’ve always worked well whether we’ve been caulking joints in wood siding, weatherproofing windows and doors, or sealing joints on interior moldings.
But building material manufacturers are always seeking to improve their products. Plywood has given way to oriented strand board, and an alternative to real stone these days is ground granite bonded under heat and high pressure to produce faux granite. The same is true for caulk.
According to an article in Fine Homebuilding magazine, there’s a new sheriff in town — hybrids that defy classification:
"Modified-silicone polymers like DAP’s Side Winder and OSI’s Advantage represent the newest type of sealant available. They are difficult to classify because they combine the chemistry and benefits of water-base, silicone and polyurethane products into one sealant. They are expensive but worth the money for sealing important outdoor areas like windows, doors and vents.
"Like latex and acrylic products," the article continues, "modified-silicone polymers are easy to (apply with a caulking) gun. Like silicones, they can be applied in extreme temperatures and can withstand rain almost immediately. Like polyurethanes, they are incredibly durable and adhere well to almost all substrate material. They are flexible, paintable with water-base paints (use a latex primer before coating with oil-base paints), have a lower VOC content than solvent-base synthetic-rubber products, cure quickly, and don’t shrink.
"The combined weatherability, durability, and flexibility of these new hybrids may make them the best product for sealing around exterior penetrations like windows, doors and vents. At this point, the only known downfalls of modified-silicone polymers are that they are expensive and new.
"Although the manufacturers put all their products through rigorous testing, modified-silicone polymers have been on the market for only a few years, not long enough to prove their worth to demanding builders and homeowners."
So, although we would plan on flashing the area correctly at some point to keep the water out, we suggest you give one of the new hybrids a try. You’ll probably need only one tube, so it won’t break the bank and it might solve the problem for longer than either you or we think.