7 percent or 5 degrees is standard in most applications.

Please post photos if you can! I saved the macv post about adding sill mouldings to windows and I couldn't quite follow what he described. I would love to see how you do it.
Nan

* Posted by macv on Mon, Jun 21, 10 at 17:27

Cellular PVC does expand and contract with heat a bit more than wood but a window shouldn't be wide enough for that to cause a problem and keeping it a light color reduces expansion. Other than that the material is expensive, virtually indestructible, and doesn't need to be painted except to clean it up or change the color. Many windows are trimmed with cellular PVC these days.

Some popular brand names for window and house trim boards are Azek, Koma, Versatex, and ATW (Advanced TrimWright).

Here is a link that might be useful: ATW

Here is a link that might be useful: the ATW link

Thanks all - we are going with the 7 degree slope. It appears pretty standard and the brick rowlock below will be also sloped at 7 degrees to match. Does this sound right? It is a masonry (painted brick) house.

I figured you meant degrees instead of percent. I likened it to a 7% grade hill but never heard of it in carpentry :-)

5 degrees is typically standard, 10 degrees would probably be too steep astetic wise so 7 should be fine for drainage as well as looks.

The ATW Standard Sill has a 15 degree slope and the Historic Sill has a 7 degree slope.

The more important part of the profile is the slope of the bottom of the sill, the drip groove, and the notch for the top of the siding so water doesn't run back against that joint and enter the building. This essential detail is missing from all but a few modern window frames.

The sill diagram has a drip groove (I take it you mean the groove that runs along the underside of the sill?) and the slope at the bottom of the sill seems adequate but I don't understand where the notch for the top of the siding is that you speak of. I can't find it on the ATW sill either.

The sill they are proposing to create for me has the protrusion of the historic sill which I like because our casing will have a backband but is not as thick, which I also like because we will have a brick rowlock under it. This is basically so the Kolbe window won't sit directly on the rowlock. Just want to make sure it is constructed correctly!

Also I don't understand how the drip groove would even work if there was a brick sill under it? Am I missing something?

For a brick veneer wall the projecting sill brick would act as the drip. The only reason to have a sub sill in that case is to accommodate jamb trim which is not always used in a brick wall.

Here is a link that might be useful: brick sill detailing

We are using a jamb trim. Our architect specced a 3 1/2 inch casing with a backband. I like the thicker than a brickmold trim from this type of house so I am happy with that, and the addition of a pvc sill to catch the casing.

I guess my real question is if the pvc sill slopes at 7 which appears to be standard and adequate, and the brick sill slopes at 7 to match the pvc sill, is that going to create moisture issues. Every thing I have seen about brick sills says that they should slope at 15 degrees and I am finding it hard to fit it all together.

A rowlock brick sill has many horizontal mortar joints which will inevitably deteriorate and fail unless carefully maintained. To extend the life of the sill it should slope at least 15 degrees and there should be carefully detailed flashing installed under it. It also helps if the brick is not very porous and the mortar joints are tight, shallow concave and well tooled. Weeps are very important to allow the the sill and the cavity to dry.

A better detail is a one piece stone, cast stone or concrete sill but it is usually more expensive so they it is rare on a private residence.

See the recommended detailing in the link below.

Here is a link that might be useful: brick detailing

Thank you! I got an email from the builder who I really trust talking about the flashing detail below the window. We are also painting the brick (primer and paint is Loxon by SW) which should also decrease the porosity, at least that is what I understand my builder to say :)