How to lay a concrete slab for air conditioner?

[robjow]

Installing a Split system and wanting to put the outdoor unit on the ground under the window there. What’s my best option? Buy a pre-made concrete slab or lay one myself? Will a solitary slab (I’ll fill the rest of the triangle up with rocks) liable to become not level over time as water and erosion shifts the sand around it?

I had heard mounting with brackets on the wall should be last option due to vibration/noise

thankyou all

[Jewelleryrescue]

Hi  @robjow 

Great your getting air con they are pretty economical these days.

Just in case no need to worry to much about air con vibration as these days they much  quiter and soft starting not like the old ones switching on at full boar and you can always slip a bit of  foam under the mounts and between the wall.

But in your space  under the window I would simply buy a  pre made slab saves alot of effort

For  example 

Anston 600 x 300mm Rectangular Concrete Paving Slab I/N: 3451549  $14.56

https://www.bunnings.com.au/anston-600-x-300mm-rectangular-concrete-paving-slab_p3451549

I would  consider siliconing on a nice stepping stone type paver to look nice or match your house possibly the following  example is slightly wider which is ok put over hang to the wall as  there is no weight on it.

610 x 406 x 30mm Travertine Natural Stone Paver I/N: 0131434  $26.99

https://www.bunnings.com.au/610-x-406-x-30mm-travertine-natural-stone-paver_p0131434

Maybe two of these on top of you cement garden block base similar style to your  house bricks

Tuscan Path 400 x 400 x 20mm Sandstone Paver I/N: 0129313 $14.24

https://www.bunnings.com.au/tuscan-path-400-x-400-x-20mm-sandstone-paver_p0129313

[EricL]

Hello @robjow 

If you are keen on making your own slab, I suggest having a quick look at this discussion - How to pour a concrete slab by @tom_builds. It's an excellent guide and shows you the basics of how to create and pour your own small slab.

However, there is an option to the concrete, I propose having a look at the Stahl 885 x 465mm 160kg Poly Air Conditioner Base. The advantage of this base is that it has drain channels in the middle of the base which guarantees that there will be no sitting water in the middle of the air-con unit.

If you need further assistance, please let me know.

Eric

[robjow]

Interesting I saw these Poly Bases but have not seem them widely in use at the AC installer websites?

Are they a good alternative to a concrete base? Are they not as stable? ( would be easier for the Compressor to be tipped over??)

Also, how do I prepare the ground for laying one of these down? Just tap down some crushed stone like you would with a regular paver?

thankyou

[MitchellMc]

Hi @robjow,

Poly bases are certainly a great option that should be considered. Please refer to your air-conditioner installation manual for specifics on what surface it must be mounted on. There might be a stipulation that it needs to go on a concrete pad.

Regarding them tipping over, that comes down to the preparation of the area. At a minimum, the ground should be hand-tamped. Crushed stone would be great for levelling the area and compaction.

Please let me know if you have further questions.

Mitchell

[robjow]

So I ended up scrapping the slab idea and just had them mounted to the wall, however have another question:

In one of the AC's the hole in the wall is visible

It's my study and I sit under the unit so am constantly looking up at it. (see below)

Is this an acceptable installation or something I should complain to the installation company about? I dont think I could patch it myself as it would probably require taking the AC off the wall which I would not want to do for fear of damaging pipes ect.

[MitchellMc]

That's quite unsightly @robjow. I'm unfamiliar with construction codes stipulating this hole must be sealed, so it probably depends on whether you are happy with the installation. It certainly wouldn't hurt to call the installer and question the visibility of the hole, as typically, the actual unit itself would cover any holes in the wall for routing pipes.  

I would certainly advise against you trying to remove the unit from the wall. In the worst-case scenario, you could likely fill the gap using paddle pop sticks to apply the filler; tedious work but doable.

Mitchell