Painting over cracked/rippled plaster walls

I'm about to paint several rooms which have plaster walls with several layers of paint on them. The surface of the walls is very uneven and there are cracks in many places. There are also places where fairly hard/thick pieces of paint are chipping off.

The painted surface has a very rough texture. It feels very chalky and porous. The house was built in the late 40's.

Here are some pictures:
http://img364.imageshack.us/img364/5052/img0617i.jpg
http://img224.imageshack.us/img224/9929/img0614.jpg
http://img362.imageshack.us/img362/38/img0608.jpg
http://img48.imageshack.us/img48/5945/img0622f.jpg

I'm looking for any advice that anyone might have about how to do this. I'd like to flatten out the ripples and cracks in the walls but I'm mainly concerned with using the right kind of materials and preparation to ensure that the paint will adhere and hopefully not chip away in the future.

I'm also going to be painting the window trim. I replaced the stop this past weekend (while replacing the windows) but the painted casing is still there. There are places on the casing where one or more of the old layers of paint have partially peeled away due to the removal of the stop. Can I fill in those places with something and sand them flat before painting over them?

Here is a picture of the window trim:
http://img20.imageshack.us/img20/8770/img0620j.jpg

Thanks for any help!

 

It wouldn't hurt to have the paint tested for lead. The walls may or may not have been painted with a lead based paint but the odds are that lead based enamel was used on the woodwork.

All loose paint [plaster too] must be scraped off. If the remaining surface is clean, it's ready to patch. I don't have any plaster skills so I usually use a setting compound like durabond to repair plaster. Minor areas can be patched, skimmed with joint compound. If the walls are still chalky after scraping, coat them with an oil base primer before applying any compound.

After all the repairs are made, coat the walls with a good latex primer. They should then be ready for a lasting paint job.

A thin layer of spackling or compound over the peeled areas, sanded and primed should eliminate the low spots. Don't forget to caulk the new piece of wood.

 

Thanks for your help.

How would I go about having the paint tested for lead? Would I need to send a sample off for testing?

The local paint store recommended that I scrape/patch and then prime the walls with zinsser cover stain, an oil based primer. You think it would be better to go with latex primer?

If scraping the loose paint just leads to more loose paint in all directions, should I just scrape the entire walls?

What type of caulk should I use for the new trim?

Thanks again.

 

I've never personally had to have paint tested for lead. I think they sell a little kit where you take a sample and mail it to a lab to be tested. Google 'lead test kits' and you'll probably find what you need. I don't think it's all that expensive.

Usually an oil base primer does better on problem surfaces that latex does. If after all the scraping is done and the wall is chalky [and you can't wash off the chalk] or shiny/slick, I'd use an oil base primer before proceeding to patching the wall. The walls will need priming after the patching is done - this time you can use either latex or oil.

It's best to scrape off all that will come off. A coat of oil base primer will help to lock the old paint down but there is no substitute for removal. While the fresh paint will help to lock down the peeling paint - at some point the loose paint will peel and take the new with it

Most any siliconized acrylic latex caulk will do. I'm partial to the 'white lightning' brand.