Chalking

[satcom]

I dont know, all the houses I do are wood siding... and I cut in old work boxes...

The box will also work on wood siding, make sure you get the proper siding lap size, installing an old work box, for a weather proof cover may not be the best method, to avoid moisture problems, the weather proof covers were not designed for switch boxes.
I found quite a few switch boxes misused for outdoor applications, and they all leached some moisture, or water, which lead to rot problems with devices and boxs.
Another thing to look at is, what if you need to use an in-use cover.

 

[stickboy1375]

The box will also work on wood siding, make sure you get the proper siding lap size, installing an old work box, for a weather proof cover may not be the best method, to avoid moisture problems, the weather proof covers were not designed for switch boxes.
I found quite a few switch boxes misused for outdoor applications, and they all leached some moisture, or water, which lead to rot problems with devices and boxs.
Another thing to look at is, what if you need to use an in-use cover.

HUH? I use taymac bubble covers, they fit just fine on an old work metal/plastic box, as far as moisture, it's all in the install of the gasket, I personally have never had a problem.

The biggest problem for me I suppose is that I dont get to the job until it is already sided...

 

[satcom]

HUH? I use taymac bubble covers, they fit just fine on an old work metal/plastic box, as far as moisture, it's all in the install of the gasket, I personally have never had a problem.

The biggest problem for me I suppose is that I dont get to the job until it is already sided...

I understand what you are saying, even intermatic in-use instructions show use of gem box, switch box, or mud ring, and they will fit no question about it, what I am noting, is this type of installation is not the best to avoid moisture, when we get repair calls, and find them rotted out, the customer wants to know why it rotted, when it was only a few years old. There are now better products out there to make a better installation.

The OP said "I installed an outdoor GFI yesterday in which the single gang box was recessed in the wall. Had to do some chalking around the cover."

If the box is flush with the surface, then the gasket will do the job, however if the an old work plastic, or metal box is screwed in to the surface, then the gasket will usually fail allowing moisture to enter the box, as I said before, mis-use of the boxes usually cause the problem.