Vinyl siding drip cap

This window mounting block was installed with vinyl siding cladding. It seemed tight at the window sash to vinyl connection. Would you recommend drip cap flashing with this installation? It was on bottom floor well below the eave. Thanks.

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That window has an integral “J” channel all around the unit…to make it easier/convenient for the siding installer. DUH!!! This style of window was invented by, of course, a window manufacturer without a full knowledge of good building science and practice. It’s being sold extensively in my area but I would never install one in my house.

Hopefully they did great flashing above, behind and on top of the the nailing fin…full Flexwrap or similar around the opening including a sloped sill plate (or premade sill drainage returns), high quality caulking between the flange/Flexwrap/sheathing membrane that the window’s installed on and another layer of Flexwrap/similar over the nailing fin after window installation and before the siding.

You may have to live with seeing that feature for a while until it shows up as a major gaff and gets changed!


You sure ask a lot of the installers. :smiley:

This type of new construction window is common in my area and works well if installed correctly. I’ve install hundreds of these windows on my projects over the years without a problem, but as Brian pointed out the installation is key, many times these windows are installed by the framers and your lucky if they even pull the building paper down over the header never mind using any type of membrane to seal the nailing fins.


What do you do at the sills to kick the water out?

Found this Article relevant to this subject;

Hope it helps.

Marcel :):smiley:

Here is another.

Carl, the windows I install have a sloped sill with weep hole to allow water to drain out.

What do you do in the sill of the opening under the window?

On a normal installation with vinyl siding we wrap the nailing fin with Vicor or some other rubber membrane then add under sill trim and cut the siding to fit. Remember no vinyl siding is 100% water tight but this method works well.