if you're new to carpentry have never installed wood trim before then this step-by-step video is
exactly where you need to start the window we're working on today is an older existing window that
previously had drywall returns which we removed in last week's video but even if you're working
on a new construction window all the techniques that we're going to be covering today will work on
those as well the trim we're using today is 1 by 4 primes pine which will be painted and installed
with no mitered corners now if you're using stain trim or a different wood that requires mitered
corners no worries I'm gonna covered miter joints in this video as well the first step is to figure
out the reveals around the window the reveal is the amount of space from the edge of the window
jamb to where the trim begins normally between 1/4 an inch to a half an inch I personally always use
a quarter inch but this window has an existing blind that needs to go back so I'm gonna have
to go with a half inch reveal to make sure that this thing fits to mark the reveals on the window
you can use a small piece of half-inch wood or combination square marking the side gems and the
top gem in a few different places just make sure once you get to the top upper corners your reveal
lines intersect making a 90-degree angle when it comes to the bottom reveal it generally needs a
larger space so that the lower sash can operate more easily so in this case we're gonna go with
a 1 inch reveal now that the reveal marks are all done let's move on to the sill and extension
jams the sill is the flat piece at the bottom of the window and the extension gems are the pieces
of trim that extend the window jambs flush to the sheet rock let's start by finding the sill
measurements the simplest way to find the silve is to take a piece of casing and lay it flat against
the wall then measure from the window jamb to the face of the casing here the measurement is 3
and 5/8 from there add the amount of distance you want to sill to extend beyond the casing normally
that's somewhere around 3/4 of an inch giving this cell a total depth of 4 and 3/8 to find the
sill length we're going to use the half-inch reveal mark that we made on the gym and this
little mock-up that I made of the extension jamb and the casing put the mock up in place and line
up the extension jam side with a half inch reveal mark next make a new pencil line on the right side
of the trim marking the finished position on the right side the window once that's done go ahead
and make a mark on the left side of the window as well before we move on I want to make sure that
you see this quarter inch reveal on the mock-up and it needs to be there if you're going to make
one of these and we're going to talk about making this reveal once all the extension jams are up on
the window now that both sides are marked take the measurement between those two lines and transfer
that to the sill then add an inch and a half to that measurement for extending the sill beyond
the casing both to the right and to the left by three quarters of an inch after cutting the sill
to length and width it's time to make those sill notches now I know that's a lot of information
coming at you all at once but stay with me because once we get past building the sill things going to
move a lot faster and be a lot less confusing to find the knotch length locate the centerline of
the window and of the sill then measure from the window center line to the right stud then center
line to the left stud deducting about an eighth of an inch in each direction once you have both
those measurements transfer those to the sill by measuring from the sills center line to find the
knotch depth measure from the jamb to the face of the drywall on the right and on the left because
sometimes those measurements are different then transfer those measurements to the sill now that
we have the notched lengths and depths all marked out on the cells time to move on to check the
squareness of the window to the wall to do that place the speed square against the window jamb
and adjust a tee bevel so that it's tight both to the wall and to the square now if I compare
the tee bevel angle to the square you can see that the wall angle is actually less than 90 degrees so
if I was to make a 90 degree perfect notch in the sill the sill would fit tight against the jam and
the corner but open up as it gets towards the end therefore to get the sill to fit tight everywhere
always use the tee bevel angle along with your layout marks to draw the notches to install the
sill line up both center lines and the one-inch reveal marks on the gym double check that the
sill is actually Square to the window adjust with shims if needed and fasten with finished nails now
if this feels all complete and everything is laid out it's time to move on to building the extension
jams but before I show you that I just want to stop and just welcome anybody who's new to the
channel and said if you want to continue to lower this please consider subscribing to the channel
and leave a comment below your voice is important to me so let's move on to extension jams to get
the width of the extension jams measure from the window jamb to the face of the drywall in four
different areas most of the time the measurements are close enough that you can split the difference
and use one number for all three pieces to get the length of the two side extension jams measure from
the sill to the upper window jamb reveal and add three quarters of an inch and you'll see why in
a second for the top extension jamb length simply measure from the right reveal to the left reveal
once the pieces are cut assemble unit with the top extension jam between the two sides and that's why
we added the three quarters of an inch glue and fasten everything was finished nails to install
simply place the whole assembly in the opening lining everything up to the reveal lines and
fasten with finished nails as a word of caution be careful not to let the nails push the extension
jams off your reveal marks you might have to use wood shims or a pry bar behind the extensions wild
nailing next go around the extension jams and mark all the quarter inch reveals like you saw
on the mock-up you can do this by using a piece of wood or in this case I'm actually going to
use a combination square to get the length of the side casing measure from the finished sill to the
upper extension jamb reveal mark once cut to that measurement install on the reveal lines nailing
into this stud with finished nails and into the extension jamb with smaller finished nails or Brad
nails now if you were using mitre trim you would simply measure just as you did from the sill to
the extension jamb review mark but this time that measurement would be the short end of a 45 degree
miter from there you could work the top piece next measuring from the short end of the mitre
on the right to the left side quarter-inch reveal mark once cut install that miter joint lastly the
left trim piece measure from the finished sill up - the short end of the previous mitre mark
cut and install a helpful tip for fitting miter joints is not to nail too close to the current
minor you're working on until you've had a chance to fit the next miter joint that if you need to
make any micro adjustments you can do so before nailing it off and I hope that makes sense if
it doesn't leave me a note in the comment section below alright back to our trim the next step is to
install the inch and a quarter half round molding which I made in the shop from the 1x4 Prime the
hip casing in the apron our last and the good thing is is that they're actually the same size
to get those measurements measure from the outside right to outside left casing and cut to pieces
to install add nails into the framing header and into the sub sill below for the apron well it has
been a long day but doesn't it look good what a difference from just the sheetrock returns to this
so a little bit of caulking priming painting all that I think it's gonna look really really good so
if you guys have any questions I know we covered a lot so please hit me up in the comments section
I'll do my best to help you guys out thanks for watching today and I'll see you in the next video