Vinyl siding window trim

Does anyone out there use a vinyl siding unzip tool to check flashing, dripcap, jchannel detail at the top of windows? If not, how are they checked? With this gap, how do I know if water is getting behind the siding and if it is, are the windows flashed properly? I haven’t looked at houses with vinyl siding until now and theses gaps around the windows worried me a bit. Can these areas at the tops of the windows be sealed with backer rod and silicone caulk?

Divekar 010.jpg


I don’t take siding off any more than I take shingles off to look underneath.

But with that said, many installers do a poor job with the windows. Do a search. Here’s a start:

I do pay attention to the insides of the windows, for example…water stains on a side jamb of the window or the casing would probably not be from sweating glass.

Well yes Larry, I’m well aware of other inspection points regarding windows, but thanks for the tip. And as far as vinyl siding goes, I believe it is pretty easy (depending on the length of the piece) to zip and unzip the lap above the window. And while I realize it does go beyond standards to do this, it would give a more complete picture of the situation (especially if it was a relatively new installation where no other clues of leakage where present). If the tool and the procedure was quick and easy, and had no downside (such as possible breakage of the siding) it might be a good to be able to see these details. That’s what I’m asking. Tell me, do you look under the first course of shingles for a starter course or at the sheathing? I’m interested in ascertaining all of the information that is available so I can give a better report. There is nothing wrong with going above the minimum. Now please, feel free to not refrain.

The down side is when you are asked why you didn’t take a look under all of it. Of course you are certainly welcome to go as far above your SOP as you wish.

Yes, I do.

As I am, within my SOP.

No there isn’t, usually, everyone has to set their own limits.

I already didn’t with the “:p” . :smiley: :wink:

I did several searches, and was only able to find general info about flashing. Nothing that addresses inspecting techniques of the exterior details. It seems to me that using that cheapo trim piece instead of a more traditional trim, precludes the use of a drip cap. Also, I’ve seen conflicting opinions on whether or not the area can be sealed with backer and caulk.

Here’s one method for windows that come with nailing fins as part of the unit but, especially for “hammer on” fins, I too like to see the drip cap.

I’ve never seen backer rod and caulk used like you describe with vinyl.

The backer rod and sealant are window mfgrs. spec. Very seldom is it done reguardless the cladding. Look at page #5 Although this is pella info the same info is on most windows.

Larry, nice photo. But what about builders that don’t use any type of wrap under the vinyl? How much of a concern is that?

It looks like the rod and caulk is going between the J channel and window.

I thought James was referring to the gap between the J channel and siding.

To me, it’s better to have it there but worse if the window isn’t flashed correctly or at all…educate, educate.:wink:

Larry, part of the flashing, as indicated by your picture, involves building wrap. Again, how significant if there is no paper–if you bend back the siding at the window and see wood, what would you say and is it “significant”?

I’ve seen that lots of times.

Theoretically, the installer is trying to keep the water on the outside of the siding but, for sure, water and sheathing don’t belong together.

Is it significant?..depends, I would say, on the amount of water penetration and damage or damage potential if new.

Unfortunately, around here you see many builders installing windows onto OSB sheathing without proper flashings. Building paper (house wrap) is not required for vinyl siding (Table R703.4) but good builders install it.

Yes I will remove siding to visualize flashing if I have any concerns. To many times I find no flashings at all. Not to many applicators around here know how to prevent moisture from entering behind causing damage in the long run.

This is with stucco for cladding. But no moisture barrier and bad flashing was/is the real problem.