Glass block basement windows

[ClutchBeta]

I'm replacing my old leaky basement windows with glass block panels fabricated by a local company.  I've done 2 out of the 7 windows, and it's going pretty well. The one problem is that there are more tool marks than I'd like on the finished edges.  My situation is a little different than what you usually see. The glass block window is set pretty much flush with the outside of the cinderblock foundation, but there are bricks outside of that.  In order to keep everything sealed and shedding water I have a 45-degree curb between the bricks and the window. The curb ends up fairly wide--maybe 2-3 inches, but still less than the width of my trowel. The attached cross-section picture shows what I'm talking about.

So here's my question: What can I do to minimize the tool marks on this fairly large and prominent strip of mortar? Could I be trying to finish it too early? Too late?  Getting into the inside corner with the trowel is kind of a pain and on the sides of the windows it's too narrow for anything but the tuck trowel.

[Jon Bon]

OK I think I understand.

You have too many tool marks (that you made) on your finished concrete edge? So you are sloping the mortar away from the window to water will shed but you are having a hard time with the finish on that?

What you can try is place the concrete while it is pretty thick and holds its shape. Get everything where you want and filled in. After about 20-30 mins you can hit the surface with a spray bottle that will allow you to work out the small imperfections. You can also use a plastic scrapper to help clean up the ridges and then broom finish for a consistent finish at the very end.

[Cadman]

I didn't see it in your diagram, perhaps it was omitted for clarity, but did you install a brickmould cap/flashing before setting the glass block? This will help shed water and your mortar curb need only be quite small (practically no tooling required). Plus it eliminates problems with thin mortar cracking from freeze/thaw cycles (if you're in that type of climate).

[ClutchBeta]

No, there's no flashing.  I'm having trouble seeing how I could put it in with the opening already finished. Wouldn't the flashing need to go underneath the top course of bricks? Here's a picture of the opening after taking the old window out. I could put flashing over the gap between the cinderblocks and bricks, but the curb would end up being the same size.

Jon Bon, I'll definitely try the spray bottle trick next time. Thanks!

[zolotiyeruki]

I think what they're saying is that the flashing should go under the first course of glass blocks, and on top of the brick.  Yes, it'd be pretty wide, but then you wouldn't need so much of a curb.

[Cadman]

Yes, I'd absolutely put flashing under the first course of blocks and bring it out over the brick now that I see your pic. A sheet metal fab shop can bend something up in 8-12' lengths if you provide a profile sketch, then all you have to do is cut it to length on-site. This will also keep moisture from absorbing into the porous top of the brick which is pretty standard here in the midwest.

[ClutchBeta]

Sorry, I've been out of town.  Do you mean like this?  I can see the advantages from an engineering point of view, but it just seems so...ugly...to have sheet metal covering up the bricks. It's already much more watertight than the jank-ass wooden windows that used to be there. You can see in the photo how much water got around them just from me hosing off the outside before starting demolition. Also, I'd have to do the same on the sides and maybe even top of the window to really seal up the gap between brick and concrete.

[Cadman]

Yep, just like that. No need for it on the sides or top, you'll still seal those gaps with mortar. it's just at the base where water sheeting against the glass will try to get in. The flashing need only overhang the brick a 1/4" or so for a drip edge and is usually available in lots of colors to match your brick so it shouldn't look too ugly. Our local box store chain even has a sheet you can download so you can design your own sheetmetal profile, pick a color, length, etc. and it's in your hands in a few days if you want something crazy.

All that said, with these being basement windows you're probably fine with straight mortar, but you're back to the tooling conundrum.

[paddedhat]

What trowel are you using? A 1-1/2" margin trowel should give you a glassy, tool mark free surface. Keep the trowel face clean by wiping it on a rag. Repeated passes should bring "cream" (which is essentially a mix of water and cement) to the surface. Pull the margin trowel from the corners toward the center,  while slightly lifting on the back edge, so it doesn't drag.  Spraying the surface can get tricky as it can lead to streaking and staining. I have done very similar mortared edges when installing very rough slate on walls. With a little practice, they should look great.