Installing an AC opening in a cinder block wall

Discussion in 'The Garage' started by manstache, Jun 19, 2017.

  1. manstache

    manstache Jed

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    I have an uninsulated garage with cinder block walls. They're painted on the outside and bare on the inside. Eventually, I'm going to insulate and you FF's have already advised me on the best way to do that. Before I do that, I want to install an opening for a large through-the-wall air conditioner. The wall I'd like to do this on is a load bearing wall about 32' long and 8' tall. There is a pressure treated 2x6 lying on the flat side along the top of the top course of blocks for the floor joists above (attic space) and rafters to sit on.

    I can punch out blocks with an air hammer I have relatively easily. I also have a spud bar and sledge hammer if I need to use them. I do not have a concrete saw and I'm not sure I really need one for punching out blocks and mortar for one opening. I realize I'll need one of those steel lintel plates going across the top of the opening to keep the above blocks from collapsing down, but I'm not sure how I'd go about installing one. For ease of closing things up, I'll probably frame the opening with pressure treated 2x8's so I can slide the AC in and secure it no problem.
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  2. VX Rider

    VX Rider Long timer

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    Just make sure your I beam lentil is at least 8 inches longer than your opening on each side, you should be fine.

    Hack out the space for the beam first.
    #2
  3. jdrocks

    jdrocks Gravel Runner

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    why not keep the AC unit high on the sidewall where it's out of the way? then you would just size the opening for the AC unit housing, conventional header, double jacks, and base plate, all PT material. temporary support under any overhead load.

    saw cut your block so you have a nice neat opening on both sides. make sure the housing drains condensate to the exterior. trim opening to suit.
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  4. manstache

    manstache Jed

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    @jdrocks, are you suggesting taking out the top 3 courses of block basically (19.5" opening) and framing up the pressure treated 2x6 that is lying up there holding the above joists? That seems a lot easier to do. How would I temporarily support that 2x6 while I'm hacking out the blocks underneath? At ceiling level in the garage it's about 8' off of the floor but about 14' off of the ground on the outside.
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  5. shovelstrokeed

    shovelstrokeed Long timer

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    You can make a lolly column out of a simple piece of pipe, a big chunk of all thread, a nut and a piece of plate. You don't use this to jack on the top plate but on the joist that would be in the middle of the hole. Doesn't need a whole bunch of pressure either. Then, once the hole is cut, slide a piece of 1/2" steel plate under the 2x6 and call it good. You can then remove the temporary lolly column.
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  6. manstache

    manstache Jed

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    That makes a lot of sense. I can do that, and I might even have a spare lolly column around here somewhere already.
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  7. shovelstrokeed

    shovelstrokeed Long timer

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    Now is a really good time to think about security.
    An air conditioner, by itself, is something that can easily be stolen. So you have to make sure it cannot be slid out from the outside.
    The hole makes a tempting access for the interior of your garage as well and your whole house if the garage is connected to it. Making the air conditioner impossible to remove helps but it is better to make sure the hole is secure from the inside as well. Given time and opportunity, a thief will breach anything but making him cut out a rebar cage could deter him enough that he will break into your neighbors garage rather than yours.
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  8. VX Rider

    VX Rider Long timer

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    Or put in a split unit...then you need only one hole through those blocks.
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  9. manstache

    manstache Jed

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    Point taken, but...if I put it at ceiling height, it's about 14' to the ground outside in an area where my German shepherds have free roam. If a thief wants to go through that to get into my garage, he can have my stuff and I'll take the insurance money. It would be a lot easier for him to break in through the entry door, anyways. A 115# wall AC unit isn't exactly easily stolen by one man, either.
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  10. manstache

    manstache Jed

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    I've gone through the split vs chassis unit debate in my head several times. A chassis unit is cheaper up front and cheaper to replace when it breaks, plus requires no special tools to flare lines or draw a vacuum.
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  11. sparkingdogg

    sparkingdogg Prisoner In Disguise

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    I wanted "nice" so I put in a mini split system. It cost a LOT of money even though I did the install myself and hired a tech to pull the vacuum and do start up. Then I had problems with the unit, several times.

    If I could do it again, I would go with a window unit in a heartbeat. Wouldn't even think about doing a mini split system, unless conditions dictated it. It's not very hard to cut an opening in block. And if the unit craps out, you get another one.

    My mini split crapped out just out of warranty. The factory guys did do me a solid, and covered the PCB under warranty. But... they shipped the wrong PCB's a few times, used UPS ground, and did a whole lot of dicking around. The mini split ended up being down for 3 months, which was the entire cooling season, and it was 100* nearly the whole time. Had it been a window unit, I could have easily popped a new one in and been done with it.
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  12. broncobowsher

    broncobowsher Long timer

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    Do you own a 4½" angle grinder? If not a trip to Harbor Freight and some concrete cut off wheels to go with it. Going primitive on the wall to open it up generally creates collateral damage to the neighboring blocks that you want to save. Making saw cuts (grinder cuts?) seperates what you want to remove from what to save.

    Are the blocks hollow or are they back filled? Sometimes they will only backfill some of the cavities to make a solid column. Expect to find vertical rebar in those.

    Sucks that it is a load bearing wall. Is it a second story it is holding up or just roof load?
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  13. gmk999

    gmk999 ____ as a Rotax

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    I wrestled with the central vs split vs window units on my last house. Even with existing ductwork as I rember the central was $2800. the split was i think $1800. window units were $150. We ended up doing the window units in the bedrooms for the few months that it gets hot here and they were enough with the room doors left open to keep the downstairs cool when we needed it. (basically weekends for three months). I figured that I would be buying a new one every few years but never had to. We split up and she sold the house after 5 years anyway.

    As far as through the block goes, Saw cut the block the size of the unit case from a mortar joint and down so you can put a lintel in the joint if needed. Make sure you have a slide in unit that can work in an 8” thick wall. Fasten the A/C housing to the block as directed . slide the AC into the housing. Easy peasy. You can cut the block with a diamond blade in either a skilsaw or prefered, a Die grinder
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  14. manstache

    manstache Jed

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    I have several 4-1/2" angle grinders and a 9" angle grinder too. I think I even have a concrete wheel for the 9" one.

    The blocks are hollow.

    The roof is a Gambrel style and there is a second floor above the garage that currently is just used to store stuff. I might finish it out at some point. The garage is totally detached from the house and about 100' away from the house.
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  15. jdrocks

    jdrocks Gravel Runner

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    the 2x6 you see is called the top plate. i don't know what kind of loads land on that plate in your circumstance, could be roof, floor, ceiling, wall, or a combination...or if the framing members are exposed. if framed 16OC, you can pick a location for the opening where you only have to temporarily support a couple framing members. the work is straight forward with common framing practices for the new opening, as if you were installing a new window for example.
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  16. Texas Aggie

    Texas Aggie Been here awhile

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  17. trailer Rails

    trailer Rails Washes hands before going to the bathroom

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  18. JCool

    JCool Long timer

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    A 120 volt unit will use twice the power of a 240.
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  19. MJS

    MJS Long timer

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    Not really. Power is measured in watts. Watts = amps x volts. The amperage at 120 volts will be twice the amperage for 240 volts at a given wattage but the power used is the same. Your electric usage/bill is measured in watts.
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  20. trc.rhubarb

    trc.rhubarb ZoomSplat!

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    As mentioned early on, don't forget to account for the pitch so it drains properly.
    Also, if it is humid where you are, don't discount the effects cooling will have with regards to condensation on your tools.
    You will find that most cases are a standard size for a given tonnage and you can just swap the removable A/C tray vs the whole unit in a failure.
    This allows you to go for a more permanent mounting solution. I've bolted mine from inside the case and then sealed with expanding foam on my old/now rental home.
    Three of them in place for almost 20 years and they are more secure than the front door.
    #20