Patching and Plastering - Wall repair

We have an old house.( 1929) We are starting to repair a wall and have found that it is a thin coat over a concrete looking wall. We thought that it was plaster, but the thickness concerned us.It is only 1/8 in thick. We bought a can of patch from a hardware store but I don't want to make the reapir wrong. The area that needs reapir is about four feet by four feet.
I read about skim coat. Is this what I need do I need an adhesive as a first step?
Can I paint over skim coat?

Thank you

It's plaster. It will look like gritty gray concrete underneath, and the thickness will vary 1/8" to 1/2" or more.

Before you repair, just to learn something about your walls, use a nail or screw to find out what the plaster is backed with.

You can skim on the patch compound right now so long as the area isn't greasy. Why does the wall need repair?

A 1/8 in layer has seperated from the gray material. It is brittle and has been painted. I have some apackling paste I plan to us to cover it. Since the ols material seperated i wanted to be sure that my patch did not.

Thanks

Clean the area to make sure there's not dirt, grease, etc left there, make sure there's no loose material in the areas as well, then you should be able to skim that with setting compound and it'll be ok. Tightcoat will probably be along here later and he could maybe give you some more tips. Good luck.

Rather than spakling paste for a four foot square patch I would suggest using a setting type joint compound like EasySand. It will go quicker if you neet multiple coats and is more like what is there so should match better. The advice about grease and clean is right on. Also see if you can scrape anymore off before you start. How easily it comes off is rather a judgment call. YOu could probabaly scrape it all off but you only want to take off what is easy. The rest will stay fine.