Patching and Plastering - Old wall new wallboard

I'm remodeling a 27 year old bathroom. I have installed a new tub and surround after much difficulty. I'm now left with replacing wallboard removed during tub installation.

Here's the problem. The old wall has what I guess is called a skim coat. It's a thin layer of plaster applied over the wallboard. How can I make the new wallboard blend with the old stuff. There is about a 1/8 inch difference. Will taping and feathering with compound work or do I need to remove all the old wall as has been suggested by a friend. Sure would like to avoid that if at all possible.

I have tried to make even cuts and my plan is to sand and bevel the cuts to make them as smooth as possible. I have no experience with drywall but I really want to tackle this task on my own. I will have some "muscle" help but nobody with much experience. Looking for any helpful suggestions.

The best way is to shim the new to the old. Use a 4 foot level to make sure it is as flat as possible. You could also use 5/8" rock and it would fit perfect.

Thanks Coops, I'm headed out to buy some 5/8 rock. I'll let you know how I do.
:thumbup:

Wow!!! I always had respect for those of you who do this kind of thing professionally but I have an even greater respect after having tried it myself.

As a retiree with some degree of do-it-yourself ability I figured I would give this remodeling a shot. I got the tub and surround installed, with much difficulty. Replacing the drywall pieces wasn't that hard since I had some help from a friend, a "home building" instructor from the high school. FINISHING the drywall and making it blend has been an ordeal. (he had surgery the day after he helped me cut the pieces and hasn't been available since then) I have applied three coats of mud and I'm still not satisfied. Maybe I'm expecting too much of myself but I want this to look good. I've invested too much time and effort for it to come out looking like crap.

My new question is... can I apply a coat of primer paint over the mudded area to see what it's going to look like after painting? If I don't like what I see can I do additional mudding over the primer? What I thought was going to be a weeklong project is turning into a month.

Yes you can apply mud over top of paint - done all the time in repair work. Although mud can easily be applied over most paints, it is very hard to sand any mud that has paint over it.

When you sand are you using a pole sander or atleast a sanding block? It is hard to get an even surface if sanding by holding the paper in your hand.

Thanks for the response.
I'm using a hand held sander with a vacuum attachment. It's worked fairly well so far.

Well it's done. It isn't perfect but better than I expected it would be with me doing all the work. I have a couple of trouble spots but nothing I can't live with. The kind of things that I know are there but I don't think any visitor will notice without me pointing it out.

Thanks again to those that responded and offered help. It was much appreciated. Now that I have discoverd this place, I'm sure I'll be back soon looking for more help.