Old Plaster Repair Questions Answered Here

I noticed you mentioned using plaster bonder sometimes. Please explain.

Liquid bonding agents were developed to help things to stick better. For example, tile setters often mix a latex bonder into their thin set mortar to insure a better bond between the tile and the cement backer board. Some thin set mortar powders come with the bonder already in the mix.

Concrete bonder is sometimes brushed or sprayed where new concrete will meet up with old, making the juncture more secure, less likely to separate later.

When repairing old plaster, what you are working with is often painted. Raw plaster doesn't stick well to paint, so brushing or rolling on a plaster bonding agent over the old painted surface just provides a much better bond between old and new.

So . . . where new plaster goes over old painted plaster, the bonder is essential. I would extend that to the use of hot mud over old plaster. Even though hot mud joint compounds contain glue (same as taping and multipurpose joint compounds do), adding some bonder to the water before mixing up a fresh batch just gives a little more assurance of a permanent fix.

Or, you could paint on the bonder over the area to be repaired, let dry then proceed. You may need to mark the fine cracks with a pencil first so you can find them later.

You can get jugs of plaster bonder at home improvement centers and at masonry supply outlets. Sometimes it is called "concrete-plaster bonder".

Online, you can find sources for plaster bonder. PlasterWeld is one of the original plaster bonders. You can find it, for example, at Larson Products.

Go to the FAQ section first, and you can read all about application procedures, etc.

I like your site. But, you've got so much information, I feel a little overwhelmed. What's the best way to start here, would you suggest?

I'm glad you like the site, and yes, there's a lot of stuff here. But there are a couple of easy ways to get a handle on your plaster repair project.

One is to subscribe to my free e-course, HOW TO REPAIR YOUR PLASTER RIGHT, here.

A second way to go the SITEMAP at the top of the navigation column on the left. This will steer you through the site based on what specific plaster problems you may be interested in.

You don't like fiberglass tape for drywall or plaster repairs. I've used it and never had any problems. What gives?

I guess it's my experience that I'm going by. I have seen so many wall and ceiling repairs - and drywall taping jobs - that were done with fiberglass tape. People call me to fix the cracks that show up some time afterwards. Does that mean that every job done with fiberglass tape will crack later? No, but why take the chance?

You want the odds in your favor. Yes, I understand the allure of fiberglass. It's so easy to use, especially doing flat drywall joints and plaster cracks. Just slap it on and cover it up.

Some people have trouble with paper drywall tape. Because they have not mastered the proper technique to put it on correctly, they run into problems with blisters (bubbles) when they go to apply the first topping coat.

The solution isn't to grab fiberglass tape. Just learn how to paper tape properly. For a more complete discussion of paper vs. fiberglass, go to drywall tape

I am using a ten inch drywall knife to mud over tape. When I go horizontally, I have trouble with the mud dribbling from the bottom of my knife. It really gets sloppy. Any suggestions?

My first thought is, maybe your mud is too thin. If you are using pre-mixed compound, you may be adding too much water. In my experience, most muds are pretty good right out of the bucket or box. If I thin at all, it's very little.Try this: load your tool and hold it up. If the mud sticks pretty well and doesn't fall off very easily, it is probably just about right. (Test with a dry tool!)

If you are mixing joint compound from bags, make it pretty thick,let set overnight and re-agitate to get rid of remaining lumps. If then you have to thin, go easy and test.

Another thought: when you make your first pass over the tape, try slanting the blade of your broadknife up slightly. In other words, less vertically with respect to the wall. This will result in a less than full width of mud for the first pass, but you can rectify that with the second or third pass.

All tools take some time to master. Awkward at first, eventually you'll be flying like a pro! Be patient with yourself, and experiment. You'll get it.

I skim coated a rough wall but when I put on the primer, some of the mud I put on started coming off. I mudded there again, but after the primer it came off again. What am I doing wrong?

I have had exactly the same problem myself. A real headache. Fortunately, it doesn't happen very often.

Two scenarios: either there is something on the painted surface that is interfering with the adhesion of your first coat, or you are using hot mud and applying it too late in the time cycle.

Okay, one at a time. Some cleaning agents can leave an invisible film that resists anything sticking to it. The solution is to wipe down the affected area with clean water and a sponge. Get that film off. Of course, be careful that you don't get water on the surrounding areas that are already coated and primed. You want a damp sponge, not soaking, and rinse it frequently.

When everything has dried, add some insurance if you like. Paint some bonder over the bad area and let dry. Then skim coat as many times as necessary to smooth and bring to level. Prime and see. You should be okay.

The other thing regards hot mud. Your hot mud batch has a chemical timer that kicks in as soon as you mix it. keep track of your time, and try to finish your application well before you run out of time and the mud starts to stiffen up on you. Especially if you are working over paint, mud applied too late in the cycle will not have time to get a good adhesion before setting up completely. So the weak bond comes loose later when the wet primer is put on.

If you put bonder on the wall/ceiling first, this is maybe less of a problem, but even then, try to finish up well in advance of the hour or two setting time of your material. You can always clean up, make a new batch and continue. Keep your batch sizes smaller when you are starting out. You will pick up speed and be able to cover larger areas as you get more experience.

I am having trouble with the hot mud I use. The bag says one hour but I only get maybe half that before it gets too hard.

Any one or more of several factors could be at work.

Hard water. Water with lots of minerals will often speed up the setting time.

I did a job out in the country once where the water available was well water. I didn't know it was hard, and I lost about half of my first batch of hot mud.

I asked the owner about the water (it did smell kinda funny), and the result was, I learned something new. Make smaller batches and go like h....

Too much agitation. If you use an electric drill and beater to mix with, you will definitely lose working time. I use a mud stick (big "potato masher") and even with that, I am careful not to over-do it. I can usually get my full working time according to the bag.

Dirty water. Use CLEAN water.

Warm water. Use cool water. If your water supply bucket is sitting out in the heat of the day, it warms up. You may want to change it every two or three hours. On the other hand, if you have a bag of slow setting material and you want things to move along faster, like doing a patch, mix your powder into WARM water and work quickly!

Inadequate cleaning of tools and containers between batches. You must clean everything well between batches. Get rid of all residues of mud from the previous batch before you mix a new one. Residues will react with the new stuff and accelerate the setting time. Tough plastic scouring pads work great for this, better than brushes.

My friend does plastering. He thinks your advice about using drywall mud to fix plaster is crazy. What do you think about that?

He's entitled to his opinion. After all, he's a professional. But, you know what, so am I. I don't believe in feeding people a lot of bull. I would not have the audacity to put up a website with all these tips and advice if they didn't work.

Listen, I understand where plasterers are coming from. Many have a low opinion of drywall, drywallers, and drywall materials. Drywall has been taking over the market for decades, and plasterers don't like it. But, in all fairness, sometimes the plasterers have a point. Here on the west coast, we have more than our share of shlocky drywall people. Some "professionals" are not!

Now, with regard to plaster versus drywall, I believe that all things considered, plaster is superior. If I were having a new house built for myself today, and felt I could afford the extra cost, I would go with veneer plaster.The big advantage over drywall is that plaster is harder and tougher. It holds up better to normal wear and tear. And you are not going to have to deal with bad drywall joints.

Many plasterers are true craftsmen, and my hat's off to them. I would NOT be happy to see plastering as a trade die out. Probably won't happen but the trade could use an infusion of new blood. True for a lot of the building trades. We need to encourage young people to consider these fields of endeavor. They have the potential to earn a good living and be able to take pride in work well done.

I recommend drywall materials to homeowners for old plaster repair because they are easier to learn to use and more "forgiving". Used properly, they will yield a perfectly adequate job. I have used them for more than thirty-five years and I have thousands of happy customers. And I live in a small city, where it would be hard to hide if I were not an honest craftsman.

I fixed the cracks in my plaster walls, but I need some help on how to match the old sand that's on the walls.

This is a pretty common problem. A lot of old plaster, especially the kind over wood lath, has a sand texture on it. Usually, it is kinda coarse and irregular. If it's any consolation, I find that patches over this kind of plaster are hard to tie in with the surrounding area.

One complicating factor is that the wall may have received multiple coats of paint over the years, so the sand is sort of rounded off, no longer real sharp.

If that is your situation, you probably don't want to go back with anything heavier than a 30 mesh sharp quartz sand.

Okay, here's what I usually do. I make a slurry of about two thirds texture compound (you can use thinned down joint compound if that's all you have on hand) and one third latex paint or PVA drywall sealer. Stir together real well and then add the 30 mesh sand.

Go light on the sand to start with, maybe only a quarter cup per quart or so of slurry. Use a paint roller - the little ones work best - and experiment on cardboard, scrap drywall, etc. Can you get it fairly even? Need more sand? Experiment until you are happy then put it on. Start with a patch in a less obvious place, like near the floor and see how it looks. Good luck!

Help! I just taped a bunch of plaster cracks, but when I cover the tape with mud, I get a bunch of blisters.

I would guess the most likely cause is that you are not getting a good coat of mud under your tape. You may be putting down too thin a band of mud, or your mud itself is so thin that you are wiping out most of it. Or, you are leaving skips in the mud bed.

It is critical that there be a solid band of mud directly over the crack and under your drywall tape if you expect to get a good secure joint. After you lay down the tape in the mud, start in the middle and wipe toward the end, then do the other half. You may have to stroke down the length more than once, but when you are done, there will be about a paper thickness of mud under the tape.

If you have a lot of blisters, wet the tape, and lift it off and replace with fresh mud and tape. Hang in there - you'll get the hang of it!

My plaster ceilings are rough and not very attractive. Plus they have lots of cracks. Should I just cover everything with drywall, or take the old texture off and just fix the cracks?

I guess it depends on how hard you are willing to work! Covering with drywall and finishing it either smooth or to look like plaster is probably less work than trying to take the old stuff off.

It is possible to tape over the plaster cracks and then skim coat the ceiling with hot mud. It will probably take at least three coats, plus a fourth if you decide to texture.

If you choose the second option, check out the page on applying skim coat.

I have sagging plaster in my old wood lath and plaster ceiling, but I really don't want to take the plaster out. I want to keep the old stuff if possible. You got any solutions to offer in my case?

Yes, fortunately there is one. A new system has been developed where you can glue the old plaster back tight against the lath, getting rid of the bulged areas. I think it's a pretty neat way to go. You can read all about it and see the video here.

I have been trying to put some texture on my wall after I fixed the cracks, but I've pretty much made a mess of things. This texturing stuff seems kinda tricky, I think.

Well, yes, it can be tricky if you don't really know what you are doing. But my take on this is simple: you don't have to be an artist or a texturing expert to do a nice job with it. I should know, since I am NOT particularly artistic. But I had the good fortune to train under a man who was really good at it, and he taught me.

So, that being the case, I have taught people myself, and even I am amazed at well so many can do once they set their mind to it. If you would be interested in some coaching by means of a DVD presentation, go to wall texturing techniques.

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