# Skim coating over "knock down" texture?



## bvz (Apr 8, 2008)

Hi there,

I did a search but I cannot seem to find anyone who has asked this question.  Pardons if it is plastered (no pun intended) all over the place.

I have drywall with what I think is called "knock down" texture all over the surface.  I used joint compound on one room to smooth it over (fill in the gaps) and it looked quite good but it is very delicate.  I can use my finger nail to damage the surface.

Now I want to do a similar thing in the kitchen, but obviously I would like it to be more resilient.  Can anyone recommend the best way to smooth this surface?  What materials to use if, in fact, skim coating is the way to go, and whether there are any good books that I should be referencing?

Thanks,
Ben


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## Square Eye (Apr 8, 2008)

Some of the fast-set drywall bag mixes are much harder when cured than the premixed versions. The downside is, you lose whatever you don't use. Mix it in small batches and get the water right by adding the water slowly. I use a plastic measuring cup to get _close_ to consistent repeated mixes, then add a tiny bit at a time to get that "right feel"
Get back on it and sand it right away though. It gets HARD if you wait too long.
You can still topcoat with the premix and get a good, easy to sand finish


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## bvz (Apr 8, 2008)

Thanks for the quick reply.  I used the powdered stuff when I did it but I don't know if it was the fast-set stuff or not (I suspect not).  I was also fairly inconsistent when adding water.  In fact, I think I recall adding a fair bit of water to make it easier to spread.

Is there anything else I should add to the mix?  Is there a hardener or anything else I should add?  Or do you think that I just over-diluted it?

Thanks again,

ben


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## Square Eye (Apr 9, 2008)

First coats are usually best done at the consistency of ice cream, firm but workable.
Top coat can spread like icing or peanut butter lol 
Top coats seal the pores where bubbles had been in the first coats and to feather out the edges with your broad trowel. 
I often work my 2nd and topcoat wet. I use a fast set or sometimes a premix for the first base coat then I knock the ridges off with a trowel. The second coat gets  a standard mix or a premix. After it sets, I wet it with a garden sprayer, 4ft at a time from ceiling to floor and scrape off the ridges again while it's soft on top. Sand it with a screen, rinsing the screen on the block in a bucket of water often. For the top coat, I use a thinned mix or a diluted premix. After it sets, I use the garden sprayer again or just a wet sponge trowel in a circular motion. It loosens the compound and works it into the pores in a slurry. Cover the entire wall with the slurry. After I'm satisfied with the joints and the corners, I let it set again. Then I use an old sanding screen to scrub off the slurry. It leaves you with a surface that looks the same on the joints or on the paper. Very smooth and perfect for spraying the primer/paint on.


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## handyguys (Apr 9, 2008)

The paint should protect the mud from scratch ability I would think. Use a coat of primer and then good paint. I like a bit more gloss in kitchens for added durability. The mud in bags is labeled for its drying time. 20 for 20 minutes, 40 for 40 minutes and so forth. That is the stuff that sets up the hardest. A pre-mixed should be fine in my opinion though. Just remember, pre-mixed still needs to be mixed and a little water added to improve consistency and workability.


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## crewguy (Apr 11, 2008)

What type of texture, if any, are you going back with? If you are trying to go "smooth" remember this:
Quick-dry "bag" mud drys very hard. Therefore, sanding is very difficult. I have been in the drywall business since 1983 and I would NEVER try to full-float a ceiling with quick-set mud! If you critique your work, getting a good looking ceiling will be almost impossible. Do yourself a favor and hang 1/4  rock over the existing ceiling. You will thank yourself later.


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## bvz (Apr 14, 2008)

Hey guys,

Thanks for all your input.  I'm still stuck doing some additional (and unexpected) electrical work at the moment, but once I am done it's on to the walls.

crewguy, thanks for your input.  I think I will take your advice and lay the 1/4 sheetrock on top of the existing ceiling.


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## plasterguy (Apr 27, 2008)

Just want to add a few thoughts, a little late in the discussion.

I do a lot of skimcoating for clients, and I have had clients who wanted to 
do their own, so they ask me for directions.  They go on to do good work.

Since I am charging my customers by the hour, I needed to develop a system early on that was reliable and consistent and efficient ...and at the same time easy to show others who want to save money.

In other words, a PLAN.  

I discovered my simple system through trial and error. I can promise a smooth finish at the end of the job, but it requires close attention to each step.

The hardest walls or ceilings to skim coat are those that are rough - heavily textured.  They usually take a minimum of three or more coats.  At the heart of the approach I use is a primary coat of quick set compound, maybe a second coat of the same, and a final with regular all-purpose mud for ease of sanding.

For others who like to do their own projects, I put up a webpage of skim coating information.  Follow the system and I think you can save yourself some work and certainly some money - you won't have to hire expensive guys like me!


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## Robinson211 (Jun 24, 2013)

A couple of other options.1:  you can add a cement additive to your wet premixed mud before you do your skim  coating. This will give your mind a much denser surface once it dries. You would then put another coat of primer on top of that. Both of these primers should be PVA (polyvinyl acetate).Option number two would be to use 90 minute joint boom pound that comes in powder and as you're mixing it had a tablespoon of cream of tartar from your kitchen cabinet. This will prevent the lime from hardening at the 90 minute point and will allow it to dry by air or evacuation. Then you will have a very hard surface.  You can  mix an entire bucket or bag at a time


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