Adding a Concrete Pad to the back of my Garage

[ME87]

Here is what I'm up against

The dimensions in yellow show where I want to pour the pad. It will be from the foundation of the house to the wall. Is this a problem? I was wondering about water getting between the pad and the foundation of the house if they aren't properly 'mated' somehow?

2nd problem is that the blue arrow show the current drainage of the back yard? What's the best way to handle this without effecting the drainage as it does flow some water when we get into monsoon season?

3rd problem is that behind the fenced in area in the corner is the A/C unit which current sits on a plastic pad of some sort. Is there going to be a way to pour concrete under it somehow if I support the A/C unit in some way while it's being poured? I'd rather not have to disconnect it from the house and move it.

It's my first house and I'm more of a fabricator than a landscaper so I need some tips? Thanks

 

[tomshep]

My first thought is have you made sure you are clear of setbacks and easements that close to your property which appears to be on the right side of your photo?

Can't help with your questions.

Tom

 

[darkk]

I would lift the A/C unit and support it with small fabricated stands. As small as you can make them. I would pour the concrete to incude the A/C unit. You can also pitch the slab a few degrees to the center from both sides and pitch the entire slab towards the back in the direction you want the water to drain for the monsoon season. There are a few good flexible sealers you can use to seal between the new slab and the existing slab to stop water penetration.

 

[hdonlybob]

Depending on the area you live in, I would check to see if codes allow a "French Drain" (which is essentially a bunch of gravel below the drain area) with a trench in the middle....the water then drains directly below into the gravel and slowly dissipates in to the soil below.
Second option is to slope your concrete to the middle, as well as to the back, so the water will still flow the same way it is now...you need a 1% slope for water to run...(which is a ~1" in 12 feet drop)
As far as water problems at your adjoining wall, put a good felt joint and caulk it well and you will have no problems....AZ does not have the freezing problem we Mid Western folks have...
One other option and just a thought for you is to pour the whole area from fence to house....then you would not have that small area around it left for mud/etc...
Also I strongly recommend using "Fiber Mesh" concrete......and going 5" thick......
Good luck and let us know what you do!
Cheers......

 

[Falcon67]

Is this a patio? #1 - I'll bet on a 5' easement at the fence. #2, if it's a patio, you should slope it back to front with a good size french drain along the front to channel water out of there. You'd want a gutter on that roof facia over the pad to take water to the A/C-drain area. Then the joint between isn't such a big deal. you could put some kind of waterproof expansion padding in there anyway. #3 - you can buy a concrete pad to slip under it or as noted you can carefully lift it and pour one under. Watch the lines and don't put too much stress on them.

 

[K'ledgeBldr]

It will be from the foundation of the house to the wall. Is this a problem? I was wondering about water getting between the pad and the foundation of the house if they aren't properly 'mated' somehow?
It's not a problem as long as the top of the new slab is at least 4" lower than the top of the house slab.
2nd problem is that the blue arrow show the current drainage of the back yard? What's the best way to handle this without effecting the drainage as it does flow some water when we get into monsoon season?
You can keep your current drainage direction by pitching the slab to the middle and back or front.
3rd problem is that behind the fenced in area in the corner is the A/C unit which current sits on a plastic pad of some sort. Is there going to be a way to pour concrete under it somehow if I support the A/C unit in some way while it's being poured? I'd rather not have to disconnect it from the house and move it.
Linesets on condensor units have little movement- and definitely not enough to raise them high enough to work a concrete slab underneath.

What's your ultimate goal for this slab? Park vehicle, patio, etc.(?)

 

[ddawg16]

Setbacks vary by city....In my area....I can pour right up to the property line....I just can't cover more than half my back yard....

On the AC unit...I would make rebar stands that sit on bricks below the bottom level of the pad....get the AC unit up as high as you can so you have room to trowl under it....when done, you just cut the rebar flush with the slab.

Instead of a french drain...I would install a drain pipe under the slab so as to reduce/eliminate the chance of errosion under the slab. You could do a french drain on the side of the slab for water to go into the pipe...and the same on the other side...

On the slab to existing foundation....drill some 3/4" holes in your exiting foundation, say 16" apart....stuff in 2' lengths of #4 rebar...dry pack the holes with motar.....this will keep the slab inline with the existing foundation.

If your worried about expansion joints...you can put down a strip of the foam between the existing slab and the new....but I'm inclinded to think you won't need it.

 

[ME87]

Wow, thanks for the replies.

I've got 2 ideas in mind. One easier than the other.

Option 1: Just to pour the slab as shown and use it for storage. As it sits, there is no way to get a car or full width trailer in the back yard. I might potentially erect a sort of patio over this area so my compressor and what not would be covered. This is the side of my house, not the back, where there is an existing patio. I do need to check the easements and set backs still but if I can only pour up to 3-5' from the fence I'll just put down rock between the slab and wall.

Option 2: Much more drastic. I move the A/C unit and pull the wood fence up and relocate the water heater in my garage (It's in the corner you now see in the right of the picture). I then install a single wide garage door in the back of the garage so that I now have a pull through garage and I could potentially park a car or trailer in the back yard on the slab. I'm not sure I'm brave enough to tackle this option yet, but I think I'm going to have the slab poured with this idea in mind.

Edit: One note on drilling into the existing slab. It is post tension concrete and it has been my impression, it's not the best idea to drill into this stuff. If any concrete experts know otherwise feel free to enlighten me as there are a couple things I'd like to mount to the floor in my garage.

 

[Dan in Pasadena]

I'm just finishing widening the existimg opening in the back wall of my 18x18 garage to a small 6x18 slab (as you propose doing in yours). The original owner didn't plan for his own opening of this wall later so he didn't make the elevations of the two slabs match; he should have as should you. He didn't frame his opening properly and I opened it to 14' wide so I had to install a structural steel frame - you'd have to do this IF you go with a single garage door. This is a big effort but if you're a "fabricator" I'd doubt this presents that big a problem for you.

 

[ME87]

Haha, if this were an all steel project I'd be set, but there is a lot of stucco, framing, concrete, A/C, and plumbing involved lol. I can handle the steel beam though.

 

[Justanoldguy]

One other option and just a thought for you is to pour the whole area from fence to house....then you would not have that small area around it left for mud/etc...

Not sure what you are looking at but it seems to
me that he is doing exactly that.
Can't see where the mud area is you talk about.

 

[hdonlybob]

Not sure what you are looking at but it seems to
me that he is doing exactly that.
Can't see where the mud area is you talk about.

My error...
I was looking a the yellow lines as concrete ending lines...not dimensions...
I am old school and never got used to the computerizes dimensions without arrows, etc....

 

[ME87]

My error...
I was looking a the yellow lines as concrete ending lines...not dimensions...
I am old school and never got used to the computerizes dimensions without arrows, etc....

I'm sure before I have this said and done, I'll have black and white drawings with arrows.

 

[K'ledgeBldr]

One note on drilling into the existing slab. It is post tension concrete and it has been my impression, it's not the best idea to drill into this stuff. If any concrete experts know otherwise feel free to enlighten me as there are a couple things I'd like to mount to the floor in my garage.

Yes. you can drill into a PTC slab- if it's been marked/located. There are companies that do just that. It's basically ground penetrating radar- they can locate the cables. Excavation of an area is not recommended- it can create weak spots. And that's not good when a cable is under 28000 psi.