Would sand make something a single leaf? or what else?

TomM · Post by **TomM** » Sat Feb 25, 2006 12:24 am

I need to plug up a small window so that it is only a single leaf and matches a concrete wall for STC.

I have a dark tint on the window so it looks black on the outside.

I want to put several layers of OSB to plug up the window, but I know the glass will act as it's own leaf if it's not tight against the window. This is impossible to do with wood.

So I was thinking, if I can fill the space between the wood and the window with sand, will they join as 1 leaf??

So when I build my inner studio walls, that will only be the second leaf??

If sand is no good, what else could I use that would fill in this space?

knightfly · Post by **knightfly** » Sat Feb 25, 2006 3:03 am

Tom, didn't we cover this a few weeks ago? Or have things changed enough to void the previous babblings??!? Steve

BTW, keep nagging me about the duct boxing frame idea so I don't completely forget when there finally comes a time

TomM · Post by **TomM** » Sat Feb 25, 2006 3:24 am

Hey Steve, We did cover it, but after reading over it again and again... I think what you were saying was based off of a 2 leaf window plug... Unless the regular insulation would create a single leaf if packed tightly enough??

The metal window frame and handles to slide it open make it too complicated to fill in all the air-gaps completely with EPS board.. So I was looking for something that could fill in all the air-gaps... sand would be kind of easy... except for the top part after I got sand filled into the bottom

I posted it separately because I was hoping to get this taken care of this weekend... and keep my other latest issues separate

The other question is how do I attach all this stuff to the concrete? Rather than renting a nail gun for such a small project (and seeing that it shouldn't require an extremely strong bond...just supporting several layers of OSB or MDF vertically in the concrete window opening, could I just use liquid nails and 2X2's around the edges (so facing in the room) with liquid nails on the side to the concrete and the side to the OSB boards. The builder's choice 290 liquid nails says it's ok for wood to concrete..

And finally I see a lot of opinions as far as what kind of wood to use against concrete in a basement. Can I just use regular OSB?

knightfly · Post by **knightfly** » Sat Feb 25, 2006 7:43 pm

If you're still talking just about the window, using glue to hold wood may be problematical; sand is HEAVY. Likewise the glass; if you're talking about putting wood at the inner surface and filling between the existing glass and wood with sand, I think you'd be asking for trouble.

Acoustically, if it held it would become a single mass; then the air gap and your inner wall would finish the equation. You can't pack insulation tight enough NOT to be considered an air space. You can, however, get it high density enough to act as a solid in terms of multi-leaf effects

If your inner wall will have at least 8" or more air space between it's mass and that of your concrete wall, I'd just put a 3 or 4 layer plug in the window (silicagel between it and the glass, as well as insulation) and LIVE with the 3-leaf you create; heavy layers in the plug, heavy layers in the inner wall, and a wide air gap between them will lessen the third leaf effect of the glass quite a bit. Sometimes you just gotta break the rules or never get it done... Steve