How To Trim A Window Exterior

There'due south goose egg like having a few gaping holes in the perfectly adept exterior walls of your firm during rainy flavor to make you fully appreciate that windows in your house will either be a blessing, or the bane of your existence. Depending on how well they're installed and the kind of flashing you use. Also, at present may be a skillful time for you to buy stock in caulk.

Yous may have been around hither a few weeks ago when MysteryMan thought he was going to take to call the exorcist because my head was spinning around on my shoulders with the strength of my rage at the improper window installation situation we had going on.In retrospect, I'thou even so not sure if I would have rather risked the stability of our relationship past trying to install them ourselves, and at this point it is what information technology is.

Then that no one else has to stumble upon the proper flashing and trimming techniques the way I did, here's what I learned…

Flashing (not the kind that goes on at Mardi Gras)

Here'due south what a window should await like that has been properly installed:

Annotation:

Flashing at the lesser that sits under the window. Everyone tells united states of america the roofing rubber we used was overkill, but do you want to have water in your firm? Me either.
House wrap should be tucked inside on the sides and bottom of the window.
Firm wrap should be folded up at the acme (and able to be folded back downwards after the window record is on.
For windows that come with an integrated nailing flange that has to be aptitude out (Marvin) they volition also accept corner pieces that must be properly placed and caulked.

Here's the problem with DIYing some of your business firm addition… all the tradesmen we've worked with like to play a game called "that'due south not my job". It goes like this "I'll install your windows and attach the corner pieces, but I won't caulk them considering… that's not my job. The siding guy does that."

Then it's up to y'all as the person who has access to the internet and therefore the wealth of the ages to be informed of these things and then that you don't accidentally trim your windows out without caulking the corner pieces. Not that I'd have any feel with that.

Ok, at present that everything is caulked, it's fourth dimension for the window record. Foil on one side, and some kind of tar based don't-get-this-stuff-on-your-wearing apparel stickiness on the other side. Seriously. Don't become it on your clothes. Or annihilation else y'all don't desire stuck to the window.

Showtime with the sides. The record gets applied 3″ over the top border (enough for the top strip of tape to overlap it) and about ane/two″ up onto the side of the window. The height should start under the top flap for the house-wrap, so this image is a little misleading.

The side pieces should run 4″ down over the flashing at the bottom.

The top piece runs 4″ out over the side pieces, and under the acme flap of business firm wrap.

And and so the summit flap gets folded down over the window tape, and the seams are taped upwardly with house wrap record.

Seems like taping might be a more appropriate term for it.

That'southward all at that place is to the flashing that needs to exist washed before y'all put on the trim. I'll show you how our condom flashing piece works when we install the siding. (Which god help me meliorate exist sooner rather than later.)

Let'southward trim something, shall we?

Trimming

First lets talk well-nigh trimming basics. Window trim is basically just four pieces of woods, no matter how you wait at it, but some ways are fancier than others. Here are some things to consider.

Materials– There are lots of materials y'all tin utilise – fiber-cement trim boards, extruded aluminum trim from the window manufacturer, or plain former wood. For amend or worse we're going with cedar siding on the house, and rough sawn cedar for all of the fascia and trim.

Sizes-Your trim should stick out past your siding, and since nosotros're using a 1″ overlaping siding we needed at to use 2x rough sawn lumber to trim in the windows. With a thinner siding you could use 1x material. Mutual widths are iv-6″. Honestly I've seen some windows with half-dozen″ siding, and unless they are huge, they await a little overwhelmed past that thick trim. But, much like permed bangs were in the eighties, information technology'south a personal pick.

Corners– You tin miter the corners or utilize a straight cut, and let me but give you lot an opinion on this. Don't miter them. One, it'southward a hurting in the ass. Two, equally the woods expands and contracts (which will exist much worse on those thin corner pieces) they're going to pull away from eachother and look similar crap). 3, the miter cut is a perfect channel directing h2o downward towards the inside of the window, which is exactly not where it should be. I cut the start trim pieces every bit miters, lined the up, and realized I was a complete moron and went dorsum to make them square cuts.

Sills– The sill tin be a larger piece of wood, it tin can have a bevel on it, or some fancy particular, or just be a straight piece of wood similar the rest of the trim. It largely depends on the way of your firm and the look you're going for. We made the trim a simple foursquare, since our wavy-edged siding is going to steal the prove. If information technology e'er gets installed.

As for the actual installing of trim, here'southward how we did it.

This is a properly flashed window:

Hey look! My start mitered board is now relegated to "spare board for measuring".

We put the measuring board in place and then measured to the lesser of the window, which ended up being adequately accurate.

After the miter/chop saw was used to cutting the side boards to length, we ran them through the table saw and took a little more than than a blade width off to adjust for the nailing flange, so that the trim would lay flat.

Which, of class, meant that the board needed to be primed once more.

Then the boards were attached, using the the spare board at the acme to brand sure they were flush.

The fasteners are stainless steel 3-1/2″ ring-shank nails. Two at the height, centre, and bottom.

And so, the elevation and bottom pieces were measured…

Same process for trimming the boards down to fit flush to the wall with the nailing flange.

Interesting, on any of our "double" windows, at that place was a protruding piece of metal where the windows were joined.

The reason for this escapes me, other than to give me an excuse to apply my chisel.

Perfect fit. Hither's our finished window.

I'll go dorsum and do touch upwardly paint on the ends and over the nails.

Besides, we'll caulk any space between the window and the trim to make sure water doesn't wick its way back inside and in that location volition exist an additional drip cap over the trim from that fun day I spent using the brake, but nosotros'll go into that when the siding fun begins.

To see how we put all these steps into action (and our strategy for DIYing the trim together with only small-scale violence) y'all tin cheque out my article and accompanying video on Old House Web: The All-time Laid Plans: DIYing Your Way Through Window Trim

As yous tin see, nosotros did go into a pretty skilful groove.

For now, things are looking much more substantial with the trim on.

And also slightly more than chaotic.

Eh, making messes is one of my natural talents.

17 Responses

Bravo! Aye, y'all SHOULD take "overkill" measures when flashing doors and windows. I have maintained private islands in the tropics (and other places) and shoddy window installations make for tons of extra piece of work downward the line. By the time you realize that your windows take been leaking for YEARS, you have a ton of costly damage to repair. When I congenital my house here in the islands, I even wrapped the rough opening lumber with protecto wrap and tucked the flashing into my courses of hardieplank. Current of air driven pelting from hurricanes hither kills, but I've replaced windows and rotten sills, framing elsewhere too. Top notch piece of work, as always. Thanks for sharing.
Not bad to properly install windows. Waste of coin to do it over vertical mulch (OSB). It's used everywhere. And will be replaced everywhere within the next decade or so. We are all suckers for good marketing of planned obsolescence. This is i of the worst examples out in that location. Don't be fooled. Proper sheathing matters.
1. I completely agree! OSB subfloors in kitchens and bathrooms volition smashing over time. Accept a pet that pees in the house? More swelling. High humidity? Y'all guessed it. Over time, using OSB will be looked back upon as the greatest mistake whatever contemporary contractor is making. Evidently and elementary, it is Non worth the savings.
How practice yous install the window when you are not taking off the siding. Under our siding is black paper from the 1950's. Do y'all accept to piece in new house wrap?
1. In case anyone else needs the reply to Pat's question:
  
  Exactly my state of affairs: house from the 50s, tar newspaper over sheathing, nether aluminum siding. The respond is, you can't unless y'all have downwards the siding. And I oasis't found any siding pros who will do it — it'southward as well hard to accept aluminum down and put information technology support and have it expect like new, and so they decline. The best shops will only tear down and replace. So if yous wanted to put in a new window, and wrap it well, you'd probably have to take down your siding, repair sheathing, wrap, install the window, and then cut the siding every bit you reinstall information technology around the new window.
  
  I took downwardly about six courses under a large window that was leaking horribly. Well-nigh of the tar newspaper was gone, the sheathing horribly rotten, ant nests, ugh. Cleaned it all out to the studs, re-sheathed, and I'grand using tyvek up to the lesser of the window and am taping information technology nether an upper course of tar newspaper which is however intact. Non perfect, but should be adept for a few years until we take the whole house re-sided. $200 in materials and a solid day'due south work.
  
  Like the page, btw! Thanks for the closeups on the taping details!
  
  br
Do yous need to caulk under the window sill? I take blood-red cedar clapps on my firm.
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prissy pics on installing a window but I accept always cut the window trim to overlap the sides. the sides should run past the lower trim so there is a natural rain baste edge and the lower trim is only cutting the width of the window and caulked to produce the baste border.
as for chads comment near strand board, there is nothing wrong with strand board. been using it at least 25 years myself and we don't take a problem with it. building a house with overhangs nosotros always run plywood there, around tub enclosures for built in tubs, but strand on the rest of the house. yous have to properly flash information technology, and run edifice paper or firm wrap to go on it dry or it will rot just as fast as plywood.
A lot of the things that are true of windows are besides true of doors. Make sure you go them well fitted and they'll serve you well letting you and friends enter and get out but keeping out the cold and unwanted neighbours. Poorly fitted and they'll exist a living nightmare in maintenance costs and cold draughts.
Wonderful article.
Practice you lot have any thoughts/recommendations virtually trying to install wood trim around windows that are already installed in aluminum siding.
Everything works fine now only nosotros would like the await of forest trim. Is in that location a skillful style to do this?
Thanks.
It looks like at that place are a lot more steps to installing window trim than I thought. I was nether the impression the kit would basically just slide into the frame, merely information technology looks like at that place is some cut involved. I'g non particularly handy, and so information technology might merely exist best for me to hire a great contractor to brand sure the job gets done properly. Thanks for the awesome information!
Great tutorial for a beginner like me! Clearly explained, well illustrated, and a fun read! Thank you!
Aid, re trimming exterior with Hardie Board trim, some how all trim (particle lath)got wet, nails rusted, perchance I over caulked, starting from scratch, questions- I accept not seen information technology on other homes, but does the trim above the garage door need a drip (?, "L" shape flashing, and all windows, if and so, then thing how well your paint status is, water (wet) gets behind siding and needs a way out or air? or is the trim left open (over garage door merely) on the underside to permit air and h2o to escape?? need Code 3 reply, so I can exercise the right thing before we become our moist weather and rain! Cheers, Rick, Rescue,CA
1. I would put z-channel over whatever piece of wood trim that surrounds a door or window (including garage doors.) You really don't want any moisture getting behind a piece of trim or you're going to have the rot and rust eventually.
  1. I meet some putting over the window and when when the trim is installed, thay add a piece over it too. Two pieces of drip cap flashing now. What is your thoughts on that?
My new windows are installed and quondam vinyl siding is removed. My contractor did not put any of the window tape on. Then he nailed crude, red cedar boards effectually the windows. Side by side he installed LP Smart siding which butts up side by side to the crude cedar trim. He said he volition install an LP siding drip edge over the top of each window.

Do we need the window record?
Doesn't the reddish cedar need stained before information technology is installed?
Do nosotros caulk betwixt the window and the red cedar?
Do nosotros caulk between the blood-red cedar and pre painted siding?
Any other suggestions? thanks
I think that you bring up a very important point of flashing the exterior top trim. Information technology is never brought up.