Old building facade painting questions

Hello everyone,

I have some questions regarding painting a facade. It is an old building with plaster on the outside, on which an old paint already sits.

1. Should it be primed before painting? How long does a primer need to dry before you can paint?
2. I read somewhere that you can mix the primer directly into the first coat, is that correct and does it work? What should the ratio be?
3. And how many coats should generally be applied? On some sites I even read about a third coat? Are 1-2 enough?
4. How long does a coat need to dry before it rains ... should painting be timed according to the weather? Or if it rains, for example, 1-2 hours afterward, does it not harm the coat?

Thanks in advance, everyone
Regards

no one has a plan?

to 1. I wondered why I applied primer.... but I would probably do it again since it's common practice, just paint the next day 2. I would skip that, it only causes trouble in the end 3. One coat of primer, then it depends on the paint. We had one with silicone that covered very well and one coat was enough for us 4. Our paint dried to the touch quite quickly, less than 30 minutes. But if I knew it would rain in two hours, I would do it another time. Although it might also work.

I would simply prime on the first day and paint the next. It’s annoying that you have to paint multiple times but you don’t do it very often anyway. Mixing primer with paint and other effort & time-saving tricks that beginners don’t know how they will turn out in the end I would therefore also skip. Sometimes you just have to manage two days without much fun

1. Should this be primed before painting? How long does a primer need to dry before you can paint?

Yes, you should do that. How long depends on what it says on the can.

2. I read somewhere that you can mix the primer directly into the first coat, is that correct and does it work? What should the ratio be?

That would be a special paint then.

3. And how often should you generally paint? On some sites, I even read about the third coat? Is 1-2 coats enough?

Our old house was painted as needed, about every 8 years: primer and one coat of white paint on top.

4. How long does a coat need to dry before it rains... should you time painting according to the weather? Or is it not a problem if it rains, for example, 1-2 hours afterwards?

Yes, it is a problem. Yes, you should check the weather forecast beforehand because rain can wash off the paint.

Basically, your questions depend specifically on the paint you choose.

A primer is often necessary if the surface to be painted is porous or sandy, or if for other reasons it cannot hold the paint. This can also be the case if a different kind of paint was applied before than now. For example, previously an expensive lotus paint, now a conventional one again.

I would not go to a DIY store and buy, but rather to a professional painter's supplier where craftsmen buy their materials.
They can give you tips on paint selection as well as how often you need to paint.

There are always innovations nowadays that can shorten the work, but they do not necessarily perform as well as conventional methods.

Edit: it is important that the plaster holds and there are no major cracks.
If needed, chip off and renew plaster partially (don’t forget the primer)
Smaller cracks can be filled with a special paint/primer.