Pella Subsill Question

[TSJHD1]

The windows for my addition are Pella wood windows. They are not clad, only primed. They have no installation fins or exterior trim applied. The exterior trim will be 5/4 PVC flat trim, applied after the windows are installed. So the window jambs will actually sit flush with the wall sheathing.

These windows were shipped with a wood subsill. You can see the actual piece on page 30 at this link: http://pellaadm.com/userdocs/Documen...tionAccess.pdf. It is the 5 3/8" x 1 7/8" subsill, part # 250H.

I have a problem. The rough openings provided on the plans, and with the window order did not allow the extra room needed to install the subsill! Lovely. I have installed exterior accessories that extend the sill before, the type that you just apply to the window/wall framing after the window is set. So I never thought much about it.

But now that the windows are on site, and after looking at the Pella PDF, I see that these are different.

I really do not want to alter the rough openings. It appears the me that the only part of the subsill that will be seen is on the outside of the window. And since my walls are 2x6, and the subsill is only 5 3/8" wide, the inner face will only end up flush with the edge of the window jambs, not the edge of the jamb extensions.

So my question is: Can I just rip off the part of the subsill that would have been under the window, set the windows, and then apply the subsill to the outside? And if so, what extra precautions should I take to make sure this method won't create any other issues (moisture intrusion into the joint between the subsill and the window/framing, or leaks of any kind)?

Should I have caught this error? My thinking is the sales rep should have made a note on the window order, or brought it to my attention.

Oh, I did frame the openings with a double sill, so it won't be too hard to make the framing change, but the subsill will still be a bit too thick.

Thanks!

Tom

[calvert]

Tom, I'm not sure if I can answer your question meaningfully, but I do have a few suggestions/observations:

1). Would trimming the subsill to the thickness that is defined by the depth of the two underside dadoes give you enough clearance for the unit to fit the rough opening? This would at least give you some subsill under the unit and you could extend out the portion that you need for an appropriate drip line.

2). I am sure the wood used in the unit is treated with a preservative/water repellent but how does cutting into it affect the nature of the depth of the treatment and consequently any warranty?

3). As far as creating a water tight joint at the interface of the subsill and sill you might check out a few items, including Sika 291,
3M 5200 or Dolfinite bedding compound. Of course all of these measures would also be backed up with a suitable flashing detail depending on the exterior cladding

As far as whether or not you should have caught this...I would say yes. And I might add that I certainly have missed things too.

[TSJHD1]

Calvert- Thanks. Great idea on #1. I'll check it out. At the very least, maybe between removing one of my framing sills, and doing what you suggest, I can make it work without having to cut (rip) the subsill.

Part of me does feel I should have caught this... but one thing's for sure... It's going on my checklist!! (Always something to learn in this business, isn't there?)

Tom

[ThingOfBeauty]

If you haven't wrapped the openings, I personally would choose to get rid of one of the rough sill pieces.
Two is definitely redundant, and it seems safer to just use the window sill that comes with the unit, everything else being equal.
If you have a lot of work invested in the current openings it might be different. A call to Pella Iowa to see the function of the sills might be in order. Also, do you know how they are fastened? Sometimes these pieces are easy to remove, other times they are glued and stapled and it will take hours and probably split a couple of the sills you're trying to keep.
I've definitely learned a thing or two from Advanced Framing. Leaving out the second sill and some of the cripples is standard procedure for me now.

[tjbnwi1]

wooD exterior unitS: Use frame dimension plus dimensions below. This dimension includes the use of standard 1-1/8" wood subsill.
frAme ROUGH
mASonry
Brickmould
width
height
+1-7/8" +1-7/8"
width
+ 3-1/8" + 6-3/8"
height
+ 3-1/8" + 4-3/4"
STD + 3/4" 3-1/2" + 3/4"
For clad and wood units with HurricaneShield® impact-resistant glass, see the product installation instructions or refer to local building code requirements.

The above is off of page 19 of the linked guide. did the specs sent include the note. If not, this is not on you, if it did........

I agree with Doug, loose one of the sills(or loose both and install a 1x sill.. You may have to plane the sub sill down a touch, if you only loose one. Treat it with the primer for Windsor One.

Tom

Tom

[TSJHD1]

Doug- I am adamantly against using 2 rough sills when I frame window openings. I think it comes from carpenters being lazy, and wanting the extra framing so it is easy to nail on the apron when trimming the window. But I've always held that by that logic, we should frame walls with 2 bottom plates so we don't have to locate the studs when running baseboard trim. Plus, I believe we frame with too much wood overall, so anytime I can eliminate some unnecessary framing I will, especially since it allows for more insulation.

However, all that being said, I framed these windows with 2 rough sills because that's what my boss told me to do. His reason was in case we had to adjust the RO to help get the windows lined up as called for on the plans (architect wants muntins of windows to line up with nearby doors). So this was one time it was good that I followed directions that went against my own convictions!

The subsills were sent loose, so no issues with removing them from the windows.

We've pretty much decided to remove 1 rough sill, and rip the subsill down to 1 1/2", only in the area that sits directly under the window. That way the exterior sill will still remain the same height. I picked up some polyurethane sealant to seal the joint where the subsill and the window meet.

And btw, these windows do sit proud of the wall sheathing by 1/4" as in the detail (the order showed 6 9/16" jambs, so I assumed they sat flush, but the actual units measure 6 13/16"-- another "slip" from Pella...), so I will also need to rabbet the exterior casings. Fun stuff indeed! (really-- I enjoy that type of work.)

Tom

[TSJHD1]

Tom- no notes re the extra height required were with the specs. We are going to alter the subsill (slightly), and with removing 1 of the rough sills, this will work fine. Thanks for the tip on treating the subsill after cutting into it.

Tom

[tjbnwi1]

If you replace the remaining sill with 5/4 will that give you the room without altering the window.

If the note was not there, this should not be on you. The Pella rep especially should have noted it. Live and learn.

Tom

[TSJHD1]

If you replace the remaining sill with 5/4 will that give you the room without altering the window.

If the note was not there, this should not be on you. The Pella rep especially should have noted it. Live and learn.

Tom

Removing just the top rough sill was quick and easy. We just ran the subsills through a table saw to get the rest of the needed clearance. On to the next task...

Tom