Loose Vinyl Siding seam under Window


This may sound a bit petty, but when I was inspecting this house it was very windy and I had heard this noise coming from this piece of siding vibrating at the seam under this window. It was locked in at both the top and bottom, however there was a lot of free play at the top where it goes in to the channel. Is something like this worth mentioning and if so, what should I recommend as a corrective fix?

Please advise,


It doesn’t look like they used any utility trim under the window at the top of the cut siding.

I guess a quick fix could be to apply some silicone adhesive behind it or do you think it should be something more drastic?

While we are on the subject of siding. Has anyone found a good flashing system for windows with integrated J-channel? I am finding several new installations with this type of window and vinyl siding. The water enters at the top and runs down the side and in behind the siding at the bottom.

Forgot the picture…


No adhesive, the vinyl needs to breath (thermal expansion). It wouldn’t be hard to pop the siding out and install what Larry has pictured, the utility trim, or “finish” trim, inside the J-channel below window.

Steve, as Larry said, there should be a piece of under sill trim there to lock the siding in place. Also, it’s never a good practice to have a butt joint under or over windows/doors. Check with the MFG. installations instruction but this should be a complete course of siding.

Randy, new construction windows are designed not to have conventional flashing. When the window is installed it should be caulked, after nailing the flange off waterproof membrane such as ice and water shield should be applied around the perimeter. Most siding and especially vinyl is not water proof and will allow water to penetrate it, this is why the vapor barrier installation is so critical and all the joints taped.
In my area, close to the ocean, it’s not uncommon to see two vapor barriers. I’ll post a link to an article from JLC about installing new construction windows.

Peter, Would you make a recommendation in this situation to have the siding pulled off around the windows and have the proper utility channel installed or just apply adhesive to the butt joint to keep it from getting caught up in the wind?

Peter, I noticed that you service the Merrimack, NH, area. I used to travel there on business quite a bit to a sister site to the company I worked for here in Salisbury, MD for 11 years. The company name was Filtronic Comtek on Continental Blvd. Small world. The jobs all went to China when a company in California bought them out in 2008.

Hi Steve, yes I would recommend it be repaired with at least sill trim. If the wind gets behind the siding it will come off pretty easy.

I was just over that way inspecting an apartment building. Lots of commercial stuff over there.

Thanks Peter and to everyone else for their comments and advice. Regards, Steve

There’s a vinyl siding installation article from an early-mid 90’s JLC with a detail to drain the water at the bottom of the side window “J” trim, and now intergral “J”, from its bottom to the “hook lip” of the horizontal siding where it moves to a panel joint or corner trim and drains away.