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Anyone have good experience in skimcoating a wall? Got tips?
My house interior walls were painted by the former owners and they did a pretty terrible job of it. I know scrapers are the way to go for all the paint snot lumps and dirt lumps they painted over. The problem I'm faced with is the painted wall surface (drywall) is very rough even after I've gone over it to nick off all the lumps. I'm not sure how they accomplished this feat as the walls I paint are much smoother over just drywall and primer. I'm thinking a skim coat of drywall joint compound will fill all these rough spots and smooth them out.
The question is what are the tricks for a smooth and quick skimcoating? Do I thin down the compound and by how much? What size and type of knife is best to use? Is a swirling motion with the knife a good way to cover?
First get a drywall sanding screen / sander and go over the painted walls.
This will sand and cut off all the dirt, bumps and crap buried in the paint. Should be able to get it pretty smooth, the dents can be then filled.
I even do this between paint coats on new work to get all the paint nibs and critters that appear. Doesn't take much time.
After that just regular drywall mud out of the bucket. 10" & 4" blades work good. Pull the mud out pretty thin. I just use a straight pull pattern. Follow by a good sanding with a fine drywall sanding screen. On new drywall work I also like to use the skim coat all over, makes the paint job easier and you can't see any areas of shading in some paints if only a couple coats are used.
Some of this occurs with some paints. It has a texture to it when applied with some rollers and there can be areas with knots, bumps and defugaties. You especially will see it in white ceilings. Sand between coats and use extra care on the final coat. A good used roller helps, seem to get more problems with new rollers. If the paint is not well shaken can also be a reason why you get a lot of nasties showing in the final paint jobs.
Thanks. I don't have those problems when I paint. I do the light sanding between coats, also mix and screen the paint to get it smooth. It's the crummy old job I need to repair.
The drywall screen doesn't get the walls smooth, they are too crappy. I really have to scrape to get the high points off, but scraping doesn't smooth it either. I guess I'm looking at quite a bit of work to undo the crummy previous job. This is way worse than any any tract house job I've ever seen with the cheapest paint and fastest job they can do.
It is essentially the whole house. And no, it would be a whole lot more work to redo the drywall - I'd still have to mud the whole place, and sand, plus te whole really big job of put up the drywall. Not to mention the expense.
I was looking to develop a better skill level at skim coating as I don't think I have a really good and efficient technique down. I'm pretty good at drywall mudding - seams, corners, etc. But skim coating is a little different skill.
It is tough to skim coat and then sand out a really bad job. The drywall mud is too soft and you tend to sand into the valley or big areas too deep.
You can skim coat with the blueboard fine plaster mix and then sand that out if you do not have the skills, manpower to get it on correctly. The real good method is to cover the walls with a mesh and skim coat that. You can buy a mesh up to 36" wide. Did it in the present house. Had to skim coat some old tongue / groove boards in the hallway and used that method.
The mesh bridges and allows the surface to sand out a lot smoother and level. Tough to describe but I can make up a mix using plaster, a recycled sanding mud dust and vary the hardest to do the big fill areas. You want the big fill areas hard and smooth and then go over with the drywall mud. This prevents sanding down into the valleys.
The techniques is something that only comes with practice. It also varies depending on the area you are trying to coat. I usually use a straight pull and then will do a arc type curve to blend in the overlap areas.
Using the mesh over the entire wall is one sure fire way to get the skim coat quite nice. It also makes the skill required a bit less. Did it a lot in the present house to save some of the old plaster walls. They were not only cracked but horribly done the first time.
You can get a wide fiberglass mesh used in roofing work and use that. They do make a wide mesh with a sticky back, it is more expensive. The mesh for roofing has no sticky back. I do a very thin coat, slap on the mesh about like wall papering and then put a fill coat over the top. That does work superb and appears to be like new work when done. Also will not crack if that has been a problem before.
It is essentially the whole house. And no, it would be a whole lot more work to redo the drywall - I'd still have to mud the whole place, and sand, plus te whole really big job of put up the drywall. Not to mention the expense.
I was looking to develop a better skill level at skim coating as I don't think I have a really good and efficient technique down. I'm pretty good at drywall mudding - seams, corners, etc. But skim coating is a little different skill.
What about renting a texture gun and giving it all a very light texture? A lot less hassle, and there are some very nice texture effects that can be easily done.
Thanks Cosmic. I think you've given me some ideas to develop a better skill level. It isn't really as bad as having fissures and holes. A lot of people probably wouldn't even care, but I do. I'm going to remember that mesh trick. That could come in handy for worse problems.
No, texture is out. I really dislike textured walls and ceilings. They collect dirt and are hard to clean. I want smooth walls.
I did some of it yesterday. I used my 12 inch knife with a lot of arcing motion to put the mud on and smooth it. In places, the drywall has dips and valleys (surprise, surprise) so some of the mud is a little thicker than in other places. But it sanded out pretty good for the most part. I'm not fond of the sanding but it is inescapable. I'll try your straight pull and then arc motion.
Do you use mudding trowels? I don't have one, but some of the stuff I've read says they use them for the smoothing coats. Thought I'd go get one because I've got a couple of dips along edges and seams in the ceiling patches that I've put about 20 coats on and they still have a dip in the middle and it isn't from buildup on the edges. I bet the mesh trick would have helped those but its too late to try that now. I'm thinking my wide blade is flexing up when I draw it.
Thanks Cosmic. I think you've given me some ideas to develop a better skill level. It isn't really as bad as having fissures and holes. A lot of people probably wouldn't even care, but I do. I'm going to remember that mesh trick. That could come in handy for worse problems.
No, texture is out. I really dislike textured walls and ceilings. They collect dirt and are hard to clean. I want smooth walls.
I did some of it yesterday. I used my 12 inch knife with a lot of arcing motion to put the mud on and smooth it. In places, the drywall has dips and valleys (surprise, surprise) so some of the mud is a little thicker than in other places. But it sanded out pretty good for the most part. I'm not fond of the sanding but it is inescapable. I'll try your straight pull and then arc motion.
Do you use mudding trowels? I don't have one, but some of the stuff I've read says they use them for the smoothing coats. Thought I'd go get one because I've got a couple of dips along edges and seams in the ceiling patches that I've put about 20 coats on and they still have a dip in the middle and it isn't from buildup on the edges. I bet the mesh trick would have helped those but its too late to try that now. I'm thinking my wide blade is flexing up when I draw it.
It really sounds like you are trying to put that drywall mud on too thick in some spots. That doesn't work that well. Not what it is intended for, that mud is only good for very thin work. It is always a trade off between getting mud that is hard enough and still be smooth to work.
The drywall stuff you mix up out of the bag is better for thicker cover spots. Same deal as with plaster, trying to retard it enough to get enough working time. The best stuff is the Diamond brand fine blueboard plaster. Even that requires some special knowledge. One problem is you need fresh materials. Lot of those home centers the stuff is on the shelf forever.
Plastering stuff is tricky. You need the right materials / knowledge / skills. I've seen few good people in that trade, is a dying art. Also need enough people, normally one just does the mixing and grunt work while others actually plaster it on there. For one person it is tough to mix and do it all, you wind up making small batches which is tricky in itself.
Trowels really work well for plastering but I've never found them that useful for skim work. I like a 10" special stainless steel blade that I found, got a big stiff plastic head. Having a vacuum sanding system is sort of critical for that type work too. I have one and never even have to wear a mask. Would starve trying to make as a plasterer. Is a tough trade to master and you need more than one person who knows what they are doing.
The mesh trick works best for what you are attempting. It makes getting it leveled out so much easier. One big thing to know is never attempt to paint a skimmed wall using drywall mud with a latex paint. The water just causes the stuff to want to go back in solution. It will come off on the roller, makes a real mess.
Use oil based paints only and a light touch on the roller to get a seal coat of paint over it first. Do not roll back into paint that is applied, get it on thin and move on. The skim coat likes to go back into solution. Even with oil based paint you can have problems if the paint is too thick or sticky.
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The problem I'm faced with is the painted wall surface (drywall) is very rough even after I've gone over it to nick off all the lumps. I'm not sure how they accomplished this feat as the walls I paint are much smoother over just drywall and primer. I'm thinking a skim coat of drywall joint compound will fill all these rough spots and smooth them out. 
Well if it is really bad.......
