Shower window flush with framing [Archive] - Ceramic Tile Advice Forums - John Bridge Ceramic Tile


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03-22-2019, 04:48 PM
Hi Everyone,

Thanks for you willingness to advise and brainstorm.

I'm working on a bathroom with a vinyl replacement window to be installed in the shower. To waterproof it I'm thinking of prepping the old wood window frame (the "rough opening" for the new replacement window) with some type of traditional rubber with adhesive, paint, or other waterproofing (any suggestions?) to send any water that gets in the window to the exterior. I read some suggestions to wrap kerdi membrane into the "rough opening" before installing the window, but seems to me like another type of waterproofing here would be more suited for wood than kerdi and that wrapping kerdi over a slope toward the shower on the inside of the house and then under the window on a slope away from shower on the exterior of the house might be problematic.

After this I was going to use kerdi membrane over cbu on the shower surround walls, wrapped into the window recess and kerdi fixed to the vinyl window frame. The main issue is that the vinyl window frame is just about flush with the wall framing.

Do you all have experience with this?

The sill extends into the room about 1.25" from the window frame. Is this sufficient for a thin strip of cbu? I could fur out the window wall, and even use two layers of cbu for that matter, so that the wall makes a nice 90 degrees with the end of the window sill. What recess amount is ideal to try to achieve with the aim of tiling right up to the vinyl window frame? I see that there exists pencil tile trim that I could use here, or perhaps a quarter bullnose type tile, or even a Schluter edge trim?

I was also thinking of nixing the recess, cutting the wooden window jamb as flush as possible with the vinyl frame, installing a single plane of cbu up close to the window frame and trimming the window with some simple pvc molding. I just can't picture how to waterproof the window frame/cbu junction well.

The picture shows a replacement window installed (I'm going to do it again because there is a weld split in the vinyl frame).

I'm also going to see if I can use this window in a different part of the house, so that maybe I can make the shower window smaller and only up high.

Thanks everyone.

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03-22-2019, 05:41 PM
I'd use some 1x on the walls to bring it out a little, then wrap the framing of the window with whatever wall board you're using. What you want in the end is for the Kerdi to be about 1/4" or so over the window jamb, which would be sealed with silicone or other sealant.

Kerdi won't adhere properly to wood, so everything has to be covered with some type of tile backer.

For what it's worth, sheetrock is a suitable backer for Kerdi, and it's what Schluter recommends. It's much easier to work with, and less expensive. However, if you prefer to use a cement board, that will work as well. It's good to know ahead of time that installing Kerdi over cement board is much more difficult, especially for a newbie, since CBU draws moisture out of the mortar very quickly.

03-22-2019, 06:30 PM
I'd approach it in a different way. Remove the old window frame and install a fixed window, creating a sill on the interior which will act as a niche as well. Movable sash on shower window is a yuck collector, although bulk water should find it's way out via the weep holes built into vinyl frame.

Old window frame would not be my preferred starting place. Most are not tied to the house frame all that well.

Actually, I'd make my own frame and have tile and waterproofing running up to glass, but it's more work and possibly a little daunting for one new to the game.

Kerdi board makes for a good window surround.

03-22-2019, 07:14 PM
Thanks Kevin and Peter.

Kevin - are you saying Kerdi needs a minimum wrap of 1/4" into the jambs or is that as far as you usually wrap it? I was going to wrap it all the way to the vinyl frame and adhere it there.

note taken about the drywall in place of cbu. like others, I'm not sure if I'm entirely comfortable with drywall and read that Durock isn't as thirsty as Hardie.

Peter- this window is one of those that wasn't tied to the frame well, it seemed to be floating. I added some framing on the sides and adhered the wood jamb to this framing and added some sill supports. Perhaps I can find another spot for this replacement window and look into changing strategies completely like you suggest.

Kerdi board as a window surround - do you mean in the jambs butting up to the window? or lining the jambs before window installation?

03-22-2019, 07:42 PM
Here's how I usually treat windows. Also put kerdifix where kboard meets window.

Sent from my VS987 using Tapatalk

03-22-2019, 07:52 PM
Thanks Ryan, that's mostly what I had in mind, minus the Kerdiboard.

I'm going with 3x6" subway tile which I guess is relatively cheap so I'll have to take another look at using Kerdi board in place of cbu. seems pretty slick

03-22-2019, 07:58 PM
On a separate note, the bathroom tub doesn't span the entire width of the room. I thought that I could use this to incorporate a nook out of the side wall by the shower head while still providing a continuous floor to wall surface for a shower curtain.

Will this present any difficulties that I, as a newbie, can't even imagine?

03-23-2019, 05:03 PM
Should be ok, I dont see any real issues.

03-25-2019, 06:53 AM
Thanks Ryan.

Another question:

I can get rid of a small strip of tile in my layout by tiling about 1 1/2" shy of a full 3' of cbu width. Will 1 1/2" of cbu and then the cbu to greenboard transistion be difficult to finish and paint over?

03-25-2019, 09:01 AM
In a dry area you can finish that joint and CBU the same as a drywall joint and it should be equally invisible.

My opinion; worth price charged.

03-25-2019, 09:17 AM
Great. It's 6 in. outside of the curtained shower, so I'll plan on that.

03-27-2019, 06:59 AM
Is there any advantage to designing the shower surround wall one way or the other?

The tile would either be set parallel or perpendicular to the tub - any difference?

And in terms of waterproofing and possible water run off to the floor from the tub?

Any thoughts? Thanks again.

03-27-2019, 07:03 AM
Also, decided to use Kerdi board, would have liked to try the Durock system, but it's a bit of a drive to pick up those components.

03-27-2019, 07:25 AM
The Durock Shower System components are available from Amazon, Leighton.

03-27-2019, 07:53 AM
Concerning design and intersection of elements.

I find it's almost always better, both looks-wise and execution-wise, to offset surfaces rather than trying to keep them in plane. There are exceptions, of course, but it's something to bear in mind.

Houses and components of houses are not truly square, flat, coplanar, level or otherwise perfect. This coming from someone who wants them to be, 'cuz his first jobs were in cabinet shops...

03-27-2019, 07:58 AM
Thanks CX,

I decided on the foam backer as opposed to the cbu or drywall and membrane as it seems the costs are comparable and the former cleaner and easier.

In such, I ruled out shipping and delivery of Durock's panels. I see the membrane up on Amazon, but not the panels.

I think I'll stick with Schulter, Durock for the next bath.

05-02-2019, 10:59 PM
Hi all,

I've just about finished furring the bathtub/shower surround back/window wall out and will now start on the side wall framing.

I have to sister a few of the 2x4's on one side wall because they're not 16 OC for the Kerdi board and because, in one corner, there isn't enough stud exposed to accommodate a Kerdi screw and washer.

Given that there's a wire run through the side wall studs, will non continuous sisters amount to a secure enough attachment point for the Kerdi?

I was going to run a sister alongside the existing studs from the ceiling to just above where the wire runs through the stud and then again starting just below the wire down to the bottom plate. With enough fasteners and even adhesive, is this adequate?


05-03-2019, 05:48 AM
The non-continuous sister will be fine, Leighton, it isn't load bearing so it only needs to support the weight of the foam board and tile. A fist full of #9 X 3" construction screws in a zig/zag pattern down the face of the sister(s) will be more than sufficient. Add adhesive if it makes you feel better.

05-03-2019, 08:18 AM
Thanks for the reassurance Dan.

I got the back wall pretty dialed in - flat and plumb. What approach do you all recommend for getting the side walls 90 degrees to the back wall? I measured the 3-4-5 triangle and the walls are actually pretty good. Is there a more precise method, without any special tools?

05-03-2019, 09:13 AM
Squaring the end walls to the back wall can be tricky. It's unlikely you'll be able to move the studs in the back corners so you'd have to alter the plane at the front. Depending on the layout (and the extent of your demo) dong that may result in a lippage issue where the backer board meets the drywall.

Really depends on how out they are.

07-18-2019, 10:06 AM
I'm now back to the shower walls after taking a break to stiffen the floors. It was a lot of work - moving ducting and plumbing, sistering a bad joist, installing a mid span beam with new footers, blocking, removing subfloor and installing 2 layers of plywood - but the floor's pretty solid now.

So now I'd like to finish the shower fixture wall. I can make the wall length to suit the tile layout, but as I'm trying to calculate exactly how long the wall should be in order to accomodate 5 horizontal 3x6 subway tiles butted up to each other, I get the sense that this is risky business. I take into account 3/32 for back wall mortar thickness, 5/16 tile thickness, 1/8 caulking between back and shower fixture wall, 30 of tile length, and another 1/8 caulk line.

The non staggering 3x6 pattern works well on the back wall framing a window and also on the wall opposite the shower fixture wall and I would like to stick with it. Also, two full tiles from the back wall is almost precisely the distance to the center of the tub drain. But if you all think that switching to a staggered pattern would be more forgiving than having to create an exact length wall than I am open to bringing the possibility of this up to everyone else involved. I figure I have to set the length of this wall based on something, and 5 full tiles seems better than ending up with, for example, 1/2 tiles on the outside corner and then wrapping the inside corner short tiles on to the back wall. But I'm also not sure what else to do.

Is there some better way to approach this? Like make the wall slightly shorter than I expect the final tiling to be and then cut the back inside corner tile slightly shorter to fit? Or wait to finalize the wall's length after installing kerdi board and tiling part of it so that I'm exactly sure what the final total tile length will be? The attached photo shows head on the wall in question, the left hand side of it is the 3 1/2" deep 90 degree turn that can be moved in either direction parallel to the wall in order to change the total wall's length.

07-18-2019, 02:40 PM
I'd hold the pattern back from the outside corner a bit and plan on trimming the tile in back corner. 1/8 or 1/4" will not be visible after you get the whole shebang up.

Another factor to consider would be how the visible edge or outside corner of tile will be handled. Bullnose? Schluter profile?

07-18-2019, 03:37 PM
Thanks Peter.

I was planning on that 3 1/2" strip being bullnose so the corner caulk line will be in the same plane as the shower fixture surface. But it could be switched so the caulk line was on the 3 1/2" strip and the bullnose on the shower fixture surface. Is this just personal preference?

Either way, does it end up that part of the 1/8" caulk line goes over top of the mortar thickness beneath the bullnose tile?

Is the 3/32" thickness a fair estimate for a 1/4" square trowel?

07-18-2019, 05:06 PM
I think I'm getting what you're driving at. Even though it's technically a change of plane, I'd grout all parts of that corner wrap. Which way to wrap is dealer's choice.

You're probably close on the 3/32, but I'm not seeing where that comes into play in the overall scheme. Unless there's some compelling reason not to, my sequence would be back wall first then end walls. I'd set from the outside corner back to inside corner knowing that I can trim to fit.

Coming from a cabinet building background, I know how the precision bug bites, but for me there has to be a little wiggle room with tile. If you haven't already, lay your tile out on floor with spacers and make a "story stick". An old technique that I find invaluable throughout the job.

07-18-2019, 05:57 PM
Sorry, I should have explained that picture. That is looking straight at the shower fixture wall with a cross section of the back wall to the right.

To determine the shower fixture wall length, I am measuring from the back wall framing and so was trying to get an idea of the thickness of the back wall kerdi board, mortar and back wall tile so that I have an idea of where the shower fixture wall tile will start (on top of the back wall tile).

I'd prefer grouting that outside corner with the bullnose tile. I think it would look better. Would you stick with the same thickness of grout as that in between the field tiles (1/16")?

Would you stick with caulking for the inside corners? At 1/8"?

I'll do that - tile back wall, then start from bullnose corner and work toward inside corner. Good idea. And the story stick.

Yeah, I see this attempt at 32's is a bit too much. But once I get an idea of the total length of that wall, I'll subtract a bit off so that I can plan on trimming the inside corner.

Thanks for the replies - I'm pretty eager to get into the tiling after all the prep. work. Hopefully it pays off.

07-18-2019, 06:59 PM
Yes on the grout joint, same as others. On many small bullnose tile the bottom sort or turns up and creates V of sorts when mated at right angle. So that joint, once grouted, will appear to be a little larger. Same goes for radius edge tile. Mock it up to check. Visual is more important than actual measurement.

Tile strikes me as an exercise in fudging here and there to get it to look right. It's just the nature of structures like houses. They're crude by cabinetmaking standards and absolutely flawed if judging by metalworking standard, FWIW.

08-03-2019, 07:43 PM
I installed the kerdi board on the back wall - it is furred out a bit and so is sitting about 1/4" off the tub deck.

I'm not sure exactly how to proceed with the end wall opposite the shower fixtures. The tub flange is essentially 1/2" high that slopes inward for about a 1/2" at which point the tub deck continues sloping in the same direction. The tub is not square to the wall in question, but the wall is flat and I didn't fur it out at all so as to avoid any depth inconsistencies where the kerdi meets the drywall.

I was planning on fixing the kerdi board just above the tub flange, most like the "flush to the flange" version that Schluter recommends. When I do this, over the 28" or so of the tub, the front of the board goes from about 3/8" in front of the top of the flange in the corner to about flush with the top of the flange at the tub's front.

If I were to go this route, the issue will be where the bottom of the tile ends up. The corner with the back wall will be fine, I think, if I fill in the 3/8" gap with kerdi fix. Here the tile can come down to the tub deck. But where the front of the kerdi board is actually flush with the tub flange, the tile won't be able to come as close to the tub deck as that in the corner.

Is furring the wall the only solution? Can the back of 5/16" ceramic subway tile be ground down?

08-03-2019, 09:18 PM
Hi again Leighton. Looks like some progress.

I'm not following all the lead in, but I'll answer the last question first. Yes, one can judiciously grind the back of tile. Sometimes just clipping the corner off with wet saw or grinder is all that's needed. Be sure to dry fit first and leave clearance between tile and tub. I wouldn't recommend trying to plane a whole tile but have done nearly that once or twice. Don't tell anyone.

You can take a tile and slide down to tub deck to check what material would have to be removed. If it involved more than a few tiles, I'd think about furring wall out more. As long as tile isn't landing directly on tub you're good. Bear in mind that wall will build out a bit with Kerdi Band and thinset.

I suspect you're finding out that almost everything deviates from the theoretical ideal. The concise modularity of tile attracts many DIY'ers only to find out that houses aren't build to same tolerances as most tile.

08-04-2019, 07:57 AM
Thanks again Peter. Slowly but surely.

When I first assessed the bathroom walls and floors I was impressed at how level and square they all were - but after flattening and shimming, boy, it could have been a bit better😄 Definitely not to the precision that tile wants. I'm embracing the anticipated art of fudging.

I've definitely had to let things go - like trying to get the fixture middles to line up on a grout line - it's close though and I'm eager to see how it all pans out. But I do plan on waiting to install the shower niche until after I have a few courses of tile down and grout lines established.

After a second look, the tile on the flange should work - I'm going to shim out the walls a bit more, plan on feathering the drywall difference, and grind tile backs a bit.

08-04-2019, 02:53 PM
Which would you recommend?

1. Feathering an 1/8"+ offset 8 ft. vertical kerdi board to drywall seam

2. Feathering an 1/16" offset 8 ft. vertical kerdi board to drywall seam and grinding the lower 1/4 of 1 1/2 subway tile (5/16" thick), or

3. grinding the lower 1/4 of 3 to 4 subway tile

08-04-2019, 03:43 PM
I might have the transition from backer to drywall be the hub of the decision wheel. One target needs to take precedence or it becomes a tail chasing exercise.

Splitting differences is often a workable solution, but only you can really make the call 'cus I can't see the whole picture from here. If you were to take some off the high spots, could that tapering situation be diminished?

I have done things from choosing the lesser of evils to shimming entire walls based on end goal and not compromising function. Budgets can figure into that too, but I had the good fortune of working for folks that knew my credo was real. "If I wouldn't do it on my own home, I won't do it to yours, and I'm a fussy SOB.

08-08-2019, 03:44 PM
I'm going to split the difference. I did some test grinding on some tile backs with a RotoZip and diamond wheel and it's a lot easier than I thought it would be.

On the window well treatment: I have the 2" Kerdi Board strips placed around the window and set in Kerdi Fix. Is it best to put screws in the top horizontal and vertical pieces and leave the sill without screws and washers? Sucks that there isn't much felt around those washers on such a thin piece of Kerdi, but so it goes with a window in the shower I suppose.

In my mess ups I noticed that Kerdi Fix doesn't adhere very well to the Kerdi board bare foam.

08-08-2019, 03:49 PM
Oh, and what's your preferred kerdi board to drywall transition? Both to ceiling and wall, not a wet area.

08-09-2019, 11:06 PM
I talked with a Schluter rep. about screws through the Kerdi board around the window. They're needed. So I'm going to fill the screw holes and the washer fang holes with Kerdi Fix.

He did say I could get away with just Fixing the Board window sill though because the Band over top of it Fixed to the window and adhered to the sill with thinset would likely additionally hold it in place.

08-23-2019, 06:05 PM
I finished installing Kerdi Band and am nearly ready to begin tiling.

I used Schluter All Set and followed the instructions on the bag for using it to apply a membrane, but that mix still came out to stiff. With more water the band definitely sits flatter to the wall.

So around the shower window where I made outside corners for the recess there are spots with a build up of 4 layers of band. Adding to this too thick an application of thinset under some layers of band, I'm looking at some buildup that I think I should address before starting to tile. In looking at these built up layers with the 3x6 subway that I will install up to them, it seems as if I will be able to stay flat with tile if I can get a thinset thickness of 3/16" or so.

But I just finished practicing setting some spare 4x4 tile with a 1/4" notch trowel and with good coverage the thinset thickness underneath is slightly more than 1/16". Does this seem correct? This leads me to believe that I should float some thinset on the walls to flatten them before I start putting up the subway tile.

If I do this, should I just feather out from the high spots of band or spread thinset over all of the wall to bring it all up to the same level as the high spots?

I've read on the forum that some haven't had any problems while laying subway tiles over up to 3 layers of band, but I'm afraid the build up I have will definitely present difficulties.

08-23-2019, 08:49 PM
Anytime I need to float out a floor or wall, I never free hand it. I apply the thinset or filler and use a straight edge to remove the excess. Ride the straight edge on the thicker area that's built out and taper it gradually down to nothing with the longest straight edge as possible. The more gradual the fill is, the less noticeable it will be.

08-24-2019, 01:39 PM
Thanks Davy. I used a 12" drywall knife as a straight edge to fan out some thinset around the window corners. I'll put a level on it later to see the difference it makes.

08-24-2019, 01:49 PM
I'm planning to put Schluter Jolly trim around the window and niche. Seeing this picture got me thinking about which direction I should orient the trim so as to best encourage water runoff from the sill.From the picture it sure looks like to me that the best way would be to make it so the sill is the vertical part in the picture. Does it matter which way its oriented?

08-24-2019, 01:53 PM
Looking at your pic, if the 4 corners of the window have the build out, I would get the outside edge all the way around straight first. I'm talking about from one built out corner to the next. Then, once that has set, use a 2 ft straight edge to go from the edge of the window to the corners, ceiling and tub.

The flatter you get the walls, the less grief you'll have installing the tiles.

08-24-2019, 02:05 PM
I'll do that - looking at that photo, I was thinking I should have just done the whole wall.

I had that wall really flat before putting the kerdi band on. I'll definitely do more to reduce build up next time.

08-24-2019, 02:17 PM
Heed Davy's advice, Leighton. While large tile can bridge some of what you're describing, those little 3 x 6 will want to follow the terrain. Smoothly blend the planes as far as you reasonably can.

Doing it now rather than trying to float little tiles even when setting (which rarely works very well) will pay off in the long game. One saving grace is that many, if not most, subway tiles have a pillowed edge which helps disguise discrepancies.

I would probably use Quadec or Rondec to visually balance both sides. I almost always use a sill, so only putting metal on 3 sides, but know how it's gonna evolve before you start. I would put the profile on the jamb and not the backwall, it will also build up a bit...makes life easier.

08-31-2019, 04:34 PM
I skimmed more thinset on all of the back and one of the side walls. I'll flatten the shower fixture wall with more thinset once I install the niche and band it.

I leveled a ledger board and set 2 rows of tiles. When I removed the ledger board, small bits of kerdi band came up with it.

The top of ledger board was about 2 inches above the tub deck and so about dead center of a 5" wide band that bridged the kerdi board to tub junction and also covered the boards lower most screws. When I set the tiles on the ledger board some thinset worked it's way in between the ledger and the wall. When I removed the ledger the next morning the outermost layer of the band adhered to the ledger and pulled away from the wall in about three spots. The area of spots of peeled away band are about 1" long by 1/2" high.

Will cleaning these spots of thinset and spreading some kerdi fix be sufficient to maintain waterproofness? It was just a layer of band that pulled away, not all of it down to the thinset between the band and the board. In order to get another piece of band over top of the spots with a 2" overlap, I would have to remove tiles in the first row that I set. I can get some photos tomorrow.

Thanks again everyone for the help.

Houston Remodeler
08-31-2019, 08:17 PM
If you have the 2 inches of overlap you'll be fine. If in doubt, add some kerdi fix

09-02-2019, 07:40 PM
Thanks Paul. I'll probably skim some Fix across them. Here's a couple photos of the Band flesh wounds (they're upside down) and the progress.

Also, I left about a 1/4" gap from the back wall end tile to the side wall because the gap decreases up to the ceiling. Can I fill this with thinset or should it be filled with caulk? The last photo shows the area.

09-03-2019, 03:21 AM
that white stuff on the kerdi is just the fuzz layer so thinset bonds better the water proof layer is in the orange layer... IMHO anyway... so dont worry at all about this.

09-03-2019, 05:27 PM
Yeah, roger that, I'm on to worrying about other things.

Should that entire gap from back wall end tile to side wall be filled with silicone?

09-07-2019, 12:04 PM
I'm looking closely at the Schluter niche that I picked up. The felt doesn't wrap around the niche corners and the white foam is visible. Looks like the majority of the edges are filled with some type of adhesive or sealant but there are spots where I can't see any.

Is this normal?

09-07-2019, 07:11 PM
They're made from 1/2" Kerdi Board, right? I've never really looked at Schluter's niches, but the ones I make look similar although I use Kerdi Fix to assemble.

I don't think you have any worries there.

09-08-2019, 09:09 AM
Yeah, it's out of 1/2". For some reason, probably the price, I was expecting something without seams on the edges.

09-08-2019, 09:17 PM
Hey Peter, how do you usually address where a vertical Schluter profile around a window meets the window's sill? Leave a gap to fill with grout or caulk?

I'm going to do like you usually do - three sides of Schluter trim and a sill. I got some bullnose tile to create a sill - am thinking this will be better than having a continuous grout line that runs the length of the window sill just upstream of a Schluter profile.

09-08-2019, 11:47 PM
I've kinda adopted sill,(window or niche) curb top, bench top and often vanity c-top all from same material as my standard fare now, but if I were doing one with bullnose I'd be inclined to go all the way around with same bullnose or profile 4 sides.

If I'm doing sill in stone or engineered stone, I almost always put "ears" on the sill and those cover the profile. I'll leave space and caulk.

Not a window but you get the idea...

09-09-2019, 05:40 AM
I like that Peter.

09-09-2019, 08:55 PM
Looks really slick Peter.

I found the porcelain bullnose at a second hand store and I'm going to use three of them to make the sill. They're black whereas the rest of the tile is green, otherwise I think I'd use the bullnose all the way around the window as well.

Will afternoon sun through the window on this black tile sill cause any issues?

09-09-2019, 10:33 PM
Will afternoon sun through the window on this black tile sill cause any issues?

I would probably hang something over the window for a couple of days after the tile are installed so they don't get too hot, if that's a possibility. You want them at room temperature for a few days during the drying process.

09-17-2019, 07:20 PM
Thanks Kevin. I set the sill pieces and covered the windows for the last few days during the afternoon to cut down on the heat.

I'm now working around the window where there's considerable tile cutting needed. I may have some help from my brother in law for part of a day and was thinking either he or I could cut tile while the other sets it.

Would it be a bad strategy to install tile all the way up both window side jambs and then all the way up the two vertical columns on the wall that flank the window? The tiles in these spots all need to be cut and this method seems like it would be most efficient for a temporary two man crew. My concern is that the grout lines might get a little skewed. I'm not all that concerned with the vertical lines as there is some play in the gaps at both of the wall's ends and the tiles here are covered up by the side wall tiles.

Any thoughts? It seems like common and best practice is to progress upwards evenly amongst the walls.

09-17-2019, 10:20 PM
Pencil out some plumb lines for your head joints based off the layout of your tile. Then layout some tile on the ground and reference the lines for your cuts, pre-cut a few rows and check them to make sure that itís a viable method for a little bit of a production style approach. For the inside jambs of the window set your edge the scribe mark and cut all your pieces and set them in one go. Of course keep a level out to maintain as your encase the window.