This is my first thread so be kind gentlemen. I have just finished rehabing a large room. I did a skim coat on the new drywall with Durock 90 minute mud (learned about it here). Came out beautiful, I’ll never go back to the standard drywall job. I love the plasteresque smoothness and want the finished walls to be as smooth as possible. To me this means that the less paint the better. My question is, do I need to prime the walls? I understand that the purpose of primer is to give an even surface for the top coat for a more even finish and also sometimes to block out stains. But these walls are very smooth and of all the same material so that a finish coat should look very uniform without the primer. Am I missing something?
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Primer also seals the under coat and helps the paint adhere. Use it.
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"I may have said the same thing before... But my explanation, I am sure, will always be different." Oscar Wilde
What is there to seal? I live in New Orleans and in hot climates the vapor barrier is supposed to be as close as possible to the outer surface. In my case the point is moot as the whole house is a sieve so there is no control of water vapor at all. The entire surface was sanded with 110 grit paper and is very smooth but dried mud is porus and will readily absorb paint to achieve a good bond.
Primer not only gives you a good surface to bond the paint to but it also "seals" the mud so it doesn't soak up all the paint, at least that's my impression, if I'm wrong correct me.
A tip for when you prime with white primer and your putting on white top coat, have the paint store put a very slight tint into the primer, you can see where you have have been and what you have missed much better.
Try one wall 1/2 and 1/2 and tell us how it looks in a good light.________________________________________________
"I may have said the same thing before... But my explanation, I am sure, will always be different." Oscar Wilde
if you want it to stay smooth spray it. otherwise use the lowest nap roller you can find. oh and don't forget the primer, bin white pigmented shellac goes on very flat.
I've always been told that hot mud will paint up a little differently than regular mud (and/or finish mud). And, from time to time, I myself have seen some difference between the glossiness of hot mud and finish mud after it was painted with no primer coat.
If you used hot mud exclusively, then, by definition, there will be no contrast between mud types.
However, I have also seen some difference in sheen between hot mud and the factory face of the rock. By "skim-coating" do you mean you applied mud over the entire wall and/or ceiling surfaces? If some of the original factory facing is still visible, then these surfaces may paint up less glossy than the hot mud areas.
As in any other case, I guess there's only one way to find out --- do it and see what happens! If you go directly to painting and are unhappy with the results, I think you could always apply a coat of primer or a second coat of paint at that point in time.
Yes I used hot mud over the entire surface and then sanded with a random orbit sander connected to a shop vac. Worked beautifully, I suppose I shortened the life of the ROS but it was worth it. Looks like plaster. If I can get away without the primer and can finish it with one coat of top coat paint, I think there is no reason to do it every time. The hot mud goes on much smoother than ready mix and I did no sanding until the skim coat was finished. I'll never do a drywall job any other way. Its so beautiful I hate to paint it. I will start another thread to see if it is possible to color the mud so that when the skim coat is finished then the job is finished.
If you are going to paint at all, you should use a primer.
Sealing - this is not wood where you have to seal the resins in but you sort of need to keep the paint out.
You have a moderately porous finish material. It is thicker in some places than others. Put paint right on that and it will soak in at different rates and give you an uneven finish. You could end up needing four coats of paint instead of one prime and two finish. Primer is more sealer and bonding agent than regular paint mixes.
You should paint it because even though it may look like plaster and be hard, it is not plaster. It will stain over time without sealing and paint..
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