I need to cut a square in wall for a A/C unit. How do I go about doing this. I have a skill saw, and a saw zaw, what is the cheapest way to make this hole? I would like a very clean straight cut. The only worry that I have is that when I start cutting chunks start falling off, which is what I don't want. Or would you maybe recommend another tool that would do the job?

 

Well, lost my reply....heres the short version

I used an angle grinder and abrasive masonry discs. I liked the control it gave me. Also the disc will cut any wire lath or flashing you may find. Might be able to use a similar disc on the circular saw, but may be tough on the saw from the grit and dust.

Eye and face protection, dust masks are a must.

Sawsall (reciprocating saw) may catch and tear out chunks..not sure.

Do you have real multicoat thick stucco with wire lath or the foamboard and thin topcoat that is pretty common now?

 

I think that is what I have wire mesh and two coats on top of that I do not think it is too thick. I Think that the disk method will probably be the one.

Anything else that you think may be helpful to know?

 

Well, if its finished inside, cut that first so you can see what you really have. Easier to patch the interior if you need to adjust

Watch for wires and pipes running though your needed area.

If you can possibly do it, use a window instead. Repairing the stucco later will be a major pain. Prior owner did that in my garage instead of just using the window 6" away..I have no idea why.

Is this a small stand alone window type A/C? Make sure the vents in the case will clear the outside surface, can't block the airflow.

 

This is what I plan on getting

Frigidaire at Lowe's: 12,000-BTU ENERGY STAR Window Room Air Conditioner

I would use the window only problem is that the windows have security bars on the them. The windows are also tall and thin, I don't even think the A/C would even fit in the window. That was why I went for the hole in the wall instead.

As far as the stucco it has not even been painted yet if I cut off a little more I can even seal it with the stucco repair stuff that comes in a tube right? I just don't want to take off more than I really have to.

 

Yes, If you have to, you could caulk it. When I replaced the old cooler in my garage, I caulked, added trim and caulked again....wide eaves on the roof, and little rain here, so no real issue.

You may want to get some flashing put up under the stucco, then put in the A/C, if weather might be an issue.

Again, I'd suggest measuring your wall thickness, then checking to make sure the vents in the case of the A/C will clear.

No off the shelf units will clear for me, but my walls are 7" thick.

 

I think I may be in your exact situation. I hope I can find one locally.

 

An angle grinder does give you good control, but unless it's a 7" grinder, it might not cut deep enough. If you can follow a line, and your vision isn't impaired by lots of dust, (that was a joke) I'd suggest a skilsaw, with a 7 1/4" diamond serrated blade. Be sure you're cutting the hole about 1/4" bigger than the box of the unit, and try to get the hole perfectly level and plumb (so that it's square... with diagonal measurements being equal). Level a line, then use a framing square to finish the outline of the opening. Try to cut as perfect of a hole as possible on the first try.

After the stucco is cut out, you'll want to install a woodbuck in the framing, (which may involve removing drywall, cutting some studs (from the inside) and adding a header above the opening) and line the perimeter of the woodbuck framing up with the edges of your masonry opening. After it's all framed in, I'd recommend lining the opening with a rubber membrane such as Grace Vycor Plus. Apply a strip on the bottom, then the sides, then the top, lapping each layer over the next, running the exterior of the membrane out onto the cut edge of your stucco. This will help protect the opening from water intrusion in the event that the sealant ever fails around the A/C box. You don't want water getting behind your stucco!

As Gunguy mentioned, be sure those fins are beyond the exterior surface of your wall. The A/C may have to be recessed into the wall a little bit to make this happen. You can always build a jamb around the interior of the opening and trim it just as if it was a window opening.

And check and see if the A/C unit needs to have any slope when you go to install it. Many units need to have a few degrees of slope so that condensation doesn't accidentally run into the house should the weep holes get plugged with debris.

 

Just got the blade, as far as the rubber membrane,can I get that from Home Depot or Lowes ? How much should it cost?
I would like to put a molding on the inside around the unit.But what about on the outside? If I make a 6" frame going around will that be enough to hold the weight of the unit, or should I put some brackets to hold it up. I plan on screwing the shell to the 2 by 6 frame and then shove in the unit.

As far as the fins, I have about 10" before I get to the fins so I think I am okay as far as that. I think I may only need about 7" at most.

 

They should have something, just ask for window and door flashing tape. There are a variety of brands... hopefully they will have one that has very sticky butyl. Some brands are better than others as far as the stickiness goes. The surfaces being bonded must be clean. It's not very expensive... maybe $20 for a roll.

Screwing the box to the woodbuck should be sufficient, provided the woodbuck is securely attached to the rest of the framing.

 

Now I know what a woodbuck is, thank you for responding.
Tomorrow will be the day!
I will let you know how it went.

As far as the outside trimming (Stucco Side), any suggestions on how to finish it, stucco, caulk, 2 by 4 wood frame?

 

The whole point of cutting a nice hole that is perfectly square, that is only 1/4" bigger than the box, is so that you can just caulk around it once you have it installed. You'd want to use some good polyurethane sealant, such as Sonneborn NP1 or Vulkem 116. Try and find sealant that's approximately the same color as your stucco for the best appearance. Cut the nozzle quite wide so that you get a good bead that's at least 1/2" wide.

 

Am I supposed to cut my square 2" wider for the 2 by 6 frame that is going around the shell of the unit?

Can you look at this?

Creative Homeowner - Dream ~ Design ~ Create.

They cut just as you said from the outside, but they took a big chunk from the inside .Is there another way of doing this without so much damage? I do plan on finishing it with a nice wood trimming, the way they did it I will have to use paint and patch up the drywall. I don't even think I have the paint to match up to the wall color. Did they over kill that job?

 

The way they did it is fine for their situation. They installed the A/C below an existing window which is good, because there is already a header over the window. You didn't indicate where exactly this A/C of yours is going, did you? Or are you just picking a spot on the wall and saying it goes "there"? As I mentioned earlier, you may need a header over this thing if there isn't one, and that will require removing some drywall inside.

But to try and answer your question, if you don't mind some wide trim around the A/C unit, you will cut a hole in the drywall that is about 1 1/2" wider on each side than the hole in your stucco. The hole in your stucco is 1/4" bigger than the A/C box. The hole you cut in the drywall would then be 3 1/4" wider than the A/C box. You would frame up a rough opening, or woodbuck, that will fit into that space (after cutting studs as needed) and it can then be attached to the existing framing. After the A/C is installed, you would need to trim the face of the opening with something wide enough to cover the cut edges of the opening. 2 1/4" casing comes to mind.

There's nothing wrong with the way they did it on that website, other than I wouldn't make the opening 1/2" bigger, since that's too much room, IMO. I also like the way they crammed about 8 steps into "figure 8". It went from no drywall on the wall to being all patched up and painted, with the A/C unit installed! LOL And the only reason they removed all that drywall was because they wanted to expose all the framing so as to tie it in a little better. Nothing wrong with that. But if you don't want to open up any more wall than you have to, I think you're on the right track.

 

Thank you so much.

Since the room is the shape of a rectangle I am putting it on one of the short sides. About 6" above an electrical outlet. About 2.5 ft above the floor. On the opposite side of the unit I have a restroom. The hope is to cool that room also by leaving to door open.Beer 4U2

 

How did this turn out? I am going to attemp the same thing on my newly built garage and am a little nervous about cutting the stucco.