flashing detail

[S.Joisey]

Any bright ideas on how to flash a through the wall air conditioner?

The last unit I installed didn't have any specs from the manufacturer, so I made do with peel n stick and coil stock. Would like something a little more tested, tried and true.

[Bill Robinson]

It would be easier to make a suggestion with a few more details.

Exposure, overhangs, exterior cladding--stuff like that.

With no more to go on that what I see here i would suggest flashing like any other through-the-wall penetration.
Integrate with the WRB if there is one and then flash in shingle style.

Drain down and out.
Down and out.
Bill R

[Happy Home]

Originally Posted by Bill Robinson

Drain down and out.
Down and out.
Bill R

Amen to that....

Are these Zoneline ? I've sprayed auto body rustproofing (black) in the bottom and up a few inches on the sides of the inside of the can. Weep holes checked.

[S.Joisey]

A through the wall AC unit into a vinyl sided wall.

I'm looking for a better way than cut a hole in the wall, stick the AC sleeve in, J all around it, and hope the water isn't too down and out (or drown and out).

The units are much different than a window, No place for head flashing, no nailing flange.

[gburnet]

Originally Posted by S.Joisey

A through the wall AC unit into a vinyl sided wall.

I'm looking for a better way than cut a hole in the wall, stick the AC sleeve in, J all around it, and hope the water isn't too down and out (or drown and out).

The units are much different than a window, No place for head flashing, no nailing flange.

How about putting the AC sleeve in, then applying P&S around the perimeter, say about 9" wide? Lap the P&S onto the inside of the sleeve for a weathertight seal. You could go so far as to add another piece of P&S on the "sill" of the sleeve, overlapping the piece on the outside. Once all that is done, trim it like a normal window - pre-assemble a frame that has a sill nosing, casing legs & head. Install that & put a head flashing on it, taped to the sheathing & with the WRB lapped over it.

[tom struble]

i think the main thing is to make sure the unit has proper pitch to the outside

[Pete Engle]

I deal with these in multistory EIFS construction all the time, and there's no easy solution.

My preferred method is to start by wrapping the RO jambs and sill with peel & stick, and integrating that with the WRB. If I can get the crews to do it, I specify a piece of 1/2" lath on the inner edge of the sill to make a back dam, and to force water towards the outside. Then we set the PTAC sleeve in the RO, making sure to pitch it properly to the outside. With EIFS, the joint between the sleeve and the EIFS is sealed with backer rod & caulk, all the way around. This works pretty well, because the sealant joint stops most of the water, and the sill pan diverts any small amount that still manages to leak in. Still, about half of them leak because either the weep holes get clogged with construction debris, or the very shallow back dam in the sleeve (some less than 1/8") gets overwhelmed when the wind blows and depressurizes the building.

If you're doing vinyl, I'd recommend still doing a backer rod and sealant joint, just do it between the peel & stick and the sleeve. Use a sealant compatible with the peel & stick. Leave a couple of weep holes in the sealant at the sill, or install weep tubes through the sealant. This is a lot of work, but that joint will be shielded from the weather by the vinyl, and will probably last the life of the house.

[Anthony B]

What about a sill pan similar to what you would use for a door or window? Place that in the RO, then set the sleeve with pitch.

SJ- are you supplying the sleeve?

Anthony

[S.Joisey]

Originally Posted by Pete Engle

I deal with these in multistory EIFS construction all the time, and there's no easy solution.

My preferred method is to start by wrapping the RO jambs and sill with peel & stick, and integrating that with the WRB. If I can get the crews to do it, I specify a piece of 1/2" lath on the inner edge of the sill to make a back dam, and to force water towards the outside. Then we set the PTAC sleeve in the RO, making sure to pitch it properly to the outside. With EIFS, the joint between the sleeve and the EIFS is sealed with backer rod & caulk, all the way around. This works pretty well, because the sealant joint stops most of the water, and the sill pan diverts any small amount that still manages to leak in. Still, about half of them leak because either the weep holes get clogged with construction debris, or the very shallow back dam in the sleeve (some less than 1/8") gets overwhelmed when the wind blows and depressurizes the building.

If you're doing vinyl, I'd recommend still doing a backer rod and sealant joint, just do it between the peel & stick and the sleeve. Use a sealant compatible with the peel & stick. Leave a couple of weep holes in the sealant at the sill, or install weep tubes through the sealant. This is a lot of work, but that joint will be shielded from the weather by the vinyl, and will probably last the life of the house.

The back dam sounds like a good idea. I used beveled siding on the sill on my last one, but it seems the wind could drive the rain up the slope. A dam in back of it would help. Backer rod will help, too.
Seems the idea is to figure that water is going to get in somehow or other, and make sure it has a way to drain out once it does.
The only thing I've added in the past is a piece of aluminum flashing at the head that comes out from the wall 4 or 5" - get the water away from the wall and make the wind work harder if it is going to blow it back.

What's a weep tube, Pete? Use any old piece of tubing? Or are these specifically made for the purpose?

[TSJHD1]

I see motels being built quite commonly with these units. They probably have that detail worked out...I'd go find one and talk with the super. There's one being built in my town right now. It has brick veneer. I could put you in touch with the builder.

Tom

[J.Buesking]

I've done several hotel exteriors and they where all pretty standard details from several different architects. They hung a sleeve out and we used caulk backer and NP1 Sealant.

[NW Architect]

None of the details "typically" in use are any good. You tend to need to add some sort of finned perimeter to the sleeve, THEN (and only then) can you treat it like all your other window openings. the challenge is that the sleeve needs to be set before the "fins" can be added.

"Fins" are always added in the sequence sill-jambs-head, and the corners lapped onto each other.

If the cladding is rainscreen, or there is a deep trim, a heavy gage, aluminum-faced peel and stick works well.

If the depth is not there, or you are working in the wet, get some brake metal angles; 3" x 1/2". Stick 3/8" x 1/8" closed cell foam weatherstripping tape to the narrow leg. Butt the weatherstripped brake metal to the sides of the sleeve. Snip and flatten the bits extending beyond the sleeve. Either nail each fin off to the wall or pop rivet to the sleeve. Seal the little pee holes at the corners.

[tom struble]

most of the residentail sleeves ive seen are open at the bottom,you cant flash against the compressor unit

[NW Architect]

Hmmm. Really? All the through wall units I've ever worked with have 4-sided sleeves.

Absent a bottom on the sleeve, besides water penetration potential, what keeps the breeze from blowing in around the mechanics?

[tom struble]

from the ones ive seen there is a chassis gasket that gets wrapped around the chassis just before the unit is fully pushed in
apparently there are different types of thru the wall sleeves