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| Trimming a window correctly is one job
that begins with good design and ends with proper technique, especially
if the design is anything more elaborate than picture-framed casing. |
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| Stool forms the foundation for every piece
of trim around a traditional window, so always begin with a dimensional
drawing, even if it's a rough sketch, so you can calculate the length
of the stool precisely. |
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To create a pleasing design, make the outside
of the window casing plumb with the ends of the window apron beneath the
stool. |
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O.D. Of The
Casing
To find the length of the stool, start by determining the O.D. of
the casing (O.D. = outside dimension; I.D. = inside
dimension). Measure the I.D. of the window jamb and add twice the width of the casing (include the width of the backband),
and twice the jamb reveal--that's the amount of jamb which is exposed
just before the inside edge of the casing. The OD. of the
casing is also the O.D. of the apron.
O.D. Of The Stool
To get the length of the stool, double the Stool & Cove Profile,
then add that measurement to the O.D. of the casing. First add
twice the thickness of the cove molding that projects past the edge
of the apron--once for each end of the apron. If the stool
has a bullnose edge, add the extension of the bullnose twice (that's
the amount the bullnose extends beyond the bottom of the stool).
Finally, add the stool reveal.
The Stool Reveal
The stool reveal is the space between the cove molding and the bullnose
on the front of the stool (see Fig. B). On window stool that doesn't
have bullnose, the reveal is the distance between the cove molding and
the bottom edge of the stool (even stool without a bullnose profile
isn't usually milled square but beveled about 5 degrees out toward the
top). The reveal can be any number--1/4 in. to 3/4 in., though the larger
the reveal, the deeper the stool. Deeper stools are more attractive
in spacious homes with tall ceilings and windows. But the reveal
should be consistent all the way around the stool--on the sides and across the front. It's easy to maintain a consistent
reveal because most stool is manufactured much wider than necessary.
The extra width is meant to be ripped off the back so that reveals can
be consistent. To determine the width of the stool pictured above,
I added the following:
1/4 in. {reveal} + 3/4 in. {cove molding} +
3/4 in. {apron} + 1 1/2 in. {the distance from the face
of the wall to the sash--minus 1/8 in. so the stool will just clear
the sash!} = 3 1/4 in. = Width of Stool |
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Simple Arithmatic
Determining the length of the stool may seem confusing,
but it's really simple arithmatic. Here's an example taken from the
window pictured above, using Windsor
One Greek Revival moldings.
O.D. OF CASING
[3 1/2 in. {casing} + 3/4 in. {backband} = 4 1/4 in.
+ 1/4 in. jamb reveal = 4 1/2 in.
4 1/2 in. X 2 {both sides} = 9 in.
Width of window jamb = 35 1/2 in. + 9 in. = 44 1/2
in. = O.D. of Casing and Length of Apron
ADD FOR STOOL & COVE
PROFILE:
3/4 cove molding x 2
= 1 1/2 in.
3/4 in. Bullnose
x 2 = 1 1/2 in.
1/4 in. Stool reveal x 2 = 1/2 in.
3 1/2 in. = Addition for Stool & Cove Profile
Total Add for Casing & Stool/Cove = 12 1/2 in.
TOTAL LENGTH OF STOOL = 48 in.
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| After ripping the stool (see Stool Reveal above), cut the stool
to length. To maintain the bullnose profile on the ends, cut outside-corner
miters on both ends. The length of the stool is measured from
the longpoint or acute angle of the miters (see "Miter Terminology"). |
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| Next, cut self-return caps from a scrap of molding, one cap
for the right end and one for the left. |
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| Glue the caps to the sill... |
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| and secure them temporarly with spring clamps. |
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| That way, when you nail through the mitre, the self-return caps
won't slide around and ruin the miter. |
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| Nail through the long-point of the miter, too. 18 ga. 1 1/4
in. brads work well. |
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| Temporarily secure the stool against the window opening.
Use a pair of scribes or a tape measure to make sure the stool is perfectly
parallel to the sill. |
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| Shim the stool away from the wall if it's closer to the sill
at one end than the other. |
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| Only then can you scribe the horns or ears. If the stool
is parallel to the sill before scribing, then once the ears are cut, the
stool be will meet the still perfectly just as the ears touch the wall. |
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| Use a small panel saw to cut the ears... |
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| and a jig saw or handsaw. |
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| Notice the second little scribe I made to follow the profile
of the jamb. |
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| That way the stool will lap over the jamb slightly and reach
closer to the sash for a tight-weather-seal fit. |
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| Fasten the stool to the sill with nails (more on fastening in
a minute). |
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| Install the jamb extension next (if it's needed) with 18ga.
brads. |
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| The casing can be mitered, glued, held with spring clamps, then
nailed in place, but... |
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| You'll get a tighter and more durable miter with a spline joint.
Be sure to clamp the material to a work bench. Hold the router firmly
against the casing, but don't push hard against the material or the router
will rock and the joint won't be flush. |
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| Use a 1/4 in. slot cutter in a router. Mark an X on the
bottom of the casing and make sure the X is always down. |
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| A spline cut from 1/4 in. mdf will fit snugley in that slot,
ensuring a perfectly flush joint. |
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| Glue the slot before inserting the spline, and glue the shoulders
of the joint, too. |
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| Be sure to rip the spline 1/8 in. narrower than the combined
depth of both slots, or the miter won't close up tightly. |
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| Nail the casing to the jamb with 18 ga. brads; nail the casing
to the wall with 15 ga. or 16 ga. 8d finish nails. |
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| Install the backband next, and start with the head. Measure
the o.d. of the casing and cut the backband head to that dimension, from
short-point to short-point (obtuse angles--see "Short-points and
Long-Points" under Trim Techniques) |
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| Glue and cross-nail the backband miters. |
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| Use the same o.d.-of-casing dimension for the ogee molding,
but measure to the long-points of the miters. Start with the head. |
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| 18ga. 1 in. brads are perfect for installing the ogee molding
and will leave small nail holes. |
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| Now the stool can be fastened up into the bottom of the casing,
with nails or screws. |
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| Install the apron next. Notice that the apron is cut with
self-returns on both ends and the o.d. of the apron, from long-point to
long-point, equals the o.d. of the casing. The stool should also
be nailed down into the apron. |
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| The cove molding--from short-point to short-point--is cut to
the same dimension as the apron. |
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| The cove m olding self-return caps must be 3/4 in. long, from
the short point to the butt cut. Be sure to cut these pieces off lengths
that are long enough to hold safely against the miter saw fence (at least
8 in. long). |
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| The cove self-return caps can be glued with hot glue or... |
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| fastened with a 23ga. micro pinner. |
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