Posts Tagged ‘joint compound’

Mirror Tar Bleeds Through Wallpaper – Prevention

June 18, 2020



The owner of this newish home in the Woodland Heights (Houston) had her handyman remove the powder room mirror and its surrounding built-in wooden frame. Mirrors are often adhered to the wall with mastic, a tar-like substance. When the mirror comes off, some of the tar residue invariably remains.

In the top photo, you can see where removing the mirror took the blobs of mastic along with it, as well as round sections of the drywall. But there are small smudges of tar still remaining on the wall.

The problem is that tar (among a lot of other substances) will bleed through wallpaper (as well as paint, and a lot of other materials).

There are stain blockers like my beloved KILZ Original Oil Based, BIN shellac based, or others, that are designed to block these stains. But I don’t trust them. For water, rust, blood, wood sap, etc., yes. But for oil-based substances like tar, I want more assurance. The best way to prevent bleed-through is not to cover the stain, but to remove it.

So I take a Stanley knife and cut into the drywall and then peel up the top layer of drywall, taking along the offending tar residue.

So now the dangerous tar is gone. But you’re left with torn drywall. This is bad for several reasons. For one thing, you have an uneven surface that will look bad under the new wallpaper (or paint). And since the top, protective layer of drywall is gone, any moisture (such as from wallpaper paste or from latex paint) will penetrate into the torn paper layer – which will swell and cause bubbling.

All of which looks pretty bad under wallpaper or paint.

So I used the product Gardz to seal the torn drywall. It is formulated to soak into the paper; then it dries hard and acts as a sealer and moisture-blocker. It won’t block stains, but it will prevent moisture from penetrating the paper and causing bubbling.

Once that was dry, I skim-floated over the entire area with joint compound. It looks rough in the photo, but once it’s dry, I’ll sand it smooth. Then I’ll give it another coat of the penetrating sealer Gardz. See last photo. Once that is dry, I’ll cover it with a coat of Roman’s Ultra Prime Pro 977 wallpaper primer, when I prime the other walls in this powder room.

All of these various products do take a while to dry, especially the joint compound as thick as I applied it. So I went to this job site a few days before the install date, to do the initial prep, so it would have plenty of time to dry before I come back for the final prep and wallpaper hang.

Weird Cracks

March 24, 2020


I have just finished stripping off wallpaper that I hung 12 years ago. The walls beneath are in perfect condition.

Except that, along just about the full height of just about every seam, I discovered these hairline cracks.

What is very odd is that the cracks have not made the wall unstable, and no material has pulled away from the wall (as often happens when you have layers of incompatible materials that will not adhere to each other – do a Search here on “delaminating”).

I believe that my original prep 12 years ago was to skim-float the walls and sand smooth. Then I wiped off the dust with a damp sponge, then followed with my favorite primer at the time, KILZ Original oil-based primer.

My thought is that the KILZ, or possibly the underlying joint compound, has separated due to tension put on it by the wallpaper seams, possibly shrinking and expanding over the years due to minute fluctuations in humidity and temperature.

Why that happened I don’t know.

This past year, I’ve had opportunity to remove wallpaper from several jobs that I hung as far back as 20+ years ago. All were over the very same original prep conditions. But none showed these little hairline cracks.

I always like to understand why something happens. That way, you have the potential to prevent it from happening in the future.

Not that I’m particularly concerned in this case. The tiny cracks have not created any problems, and the wall is not unstable.

I felt perfectly comfortable hanging the new paper right on these walls – however, I made very sure that no seams of the new paper landed exactly on top of those cracks. That would eliminate the chance of any stress put on the cracks by the new seams potentially causing them to weaken and pull away from the wall.

Washing Texture Off of Walls

March 5, 2020


The owners of this new-build home in the Garden Oaks neighborhood of Houston knew that they wanted wallpaper in the dining room and powder room. So they instructed the builder to not texture the walls.

Well, as often happens, the drywall/paint guys didn’t get the message, so while they were spraying texture on the other walls in the home, they also textured the dining and powder rooms (sorry, no picture).

But – they got stopped before they primed or painted. This is good.

The textured surface had to be smoothed before wallpaper could go up. I’m quite good at skim-floating, and I quoted the homeowners a price for me to float and sand the walls smooth.

But the homeowner is also pretty handy. He opted to smooth the walls himself.

Since no primer or paint had been applied, the texture on the walls was raw mud (drywall joint compound). With no coating on it, this stuff is water-soluble. That means that the homeowner could simply wipe the walls with a wet sponge to remove the texture.

Well, it’s actually a bit more than that. You have to wet the walls well, and keep on scrubbing, to the point where the joint compound / texture softens up and can be scraped off the wall with a stiff putty knife, or scrubbed off the wall with a drywall sponge.

And that’s what the homeowner did. He did such a good job that he cleaned the walls all the way down to the bare drywall. That’s what you see in the first two photos. This guy was way more thorough and meticulous than any “professional” I’ve seen out there.

The best primer for bare drywall is Gardz (third photo). It penetrates and seals both the paper face of the drywall, as well as the joint compound “mud” that is troweled over the joints and tape (see white areas in photos).

So my task for today was not to work on smoothing the walls, because the homeonwer had done such a great job of that. OK, well, I did do a little tweaking in a few areas. But primarily, what I did today was roll on (and cut into the corners and edges) a good coat of Gardz.

Besides sealing drywall, Gardz is a good primer for wallpaper. So once the primer was applied and then dried (about an hour), the room was ready for wallpaper.

Sticking to a Glossy Surface

January 15, 2020


Not many materials like to stick to a glossy surface. So today, when I had to skim-float a wall to smooth it, in order to help the joint compound adhere to the existing paint, I first wiped the wall down with Liquid Sandpaper – a chemical formulated to knock off the gloss and prepare the surface to accept the coating you are wanting to apply on top of it.

Smoothing Knock-Down Textured Wall

December 20, 2019


This newish home in Kingwood (northeast Houston) had a typical suburban tract home knock-down texture. This would look horrible under the new wallpaper, as well as interfere with complete adhesion.

So I skim-floated the wall by troweling on joint compound (like plaster), and then sanded smooth. After wiping sanding dust off the wall with a damp sponge, I primed with Gardz, a penetrating sealer / primer by Zinsser. Sorry, no “during” photos. 😦

The last photo shows the smoothed surface, primed and ready for wallpaper. (The dark spots are where the original texture was thick and therefore peeking out from under the smoothing compound.)

Patching Gap Around Light Fixture

November 8, 2019

The original light fixture had a rectangular base. The new one had a base that was barely larger than the electrical box. The electrician ended up with a slight gap on the left side of the box.

The wallpaper would most likely bridge that gap and look just fine. But since there was a slight difference in height between the wall and the base of the fixture, I wanted to close the gap to minimize chances of a visible pooch or bubble around the fixture.

I bought some drywall repair kits, and ended up using the one that had a thin aluminum mesh patch. I cut it to fit around the electrical box, using a few scraps to fill in gaps.

I then used drywall joint compound (“mud”) to smooth over the area. It took two of these skim coats, and a lot of time holding my heat gun to get everything to dry. Once sanded, it was nice and smooth.

A coat of Gardz penetrating sealer / primer, and the patched area was ready for wallpaper.

Elapsed time: Two hours.

This saved the homeowner having to hire “a guy” to do the repairs – and most likely, I would have had to “fine tune” whatever he did, anyway.

KILZ Stain Blocker to Cover Green Ink

October 26, 2019


See the green vertical line to the right of the paint can? The previous wallpaper installer probably had a little white wall showing at a seam, so used ink that matched the color of the wallpaper to disguise it.

Ink (along with other substances, like blood, rust, water stains, oil, tobacco, mildew, wood sap, and others) can bleed through joint compound, paint, and wallpaper. Sometimes it takes a few months or years.

So it’s important to discover these stains, and to treat them with a stain-blocking sealer. Water-borne products simply don’t work, no matter what the label claims. Shellac-based sealers like BIN are good. But I like KILZ Original, the oil-based version.

Knock-Down Texture on a Wall

October 3, 2019


Here is a new sheet of drywall, installed to repair damage from flooding during Hurricane Harvey. The drywall is grey.

The splats of white stuff you see on top is joint compound that has been sprayed on, and then “knocked down” to about a 1/8″ height by a worker with a wide taping knife.

This creates a texture on the wall that is pretty common in newer suburban homes.

The surface should be primed, and then a coat of paint can be applied.

In the case of wallpaper, the wall would have to be “skim floated” and sanded smooth, to get rid of the texture.

Getting Smoothing Compound To Dry

June 13, 2019


The walls in this powder room were textured. (see top photo) To ensure that the new wallpaper looks good, and that it has a solid surface to cling to, the walls need to be smoothed. This is called floating, or skim coating, and I do a lot of it here in Houston. To do that, I trowel on a plaster-like substance, let it dry, then sand it, vacuum up the dust, wipe residual dust off the walls with a damp sponge, and then prime.

What takes the most time is waiting for the smoothing compound (drywall joint compound, which we also call “mud”) to dry. If the texture is heavy, often it has to dry overnight. The downside of this is that it adds an extra day of labor and expense. But when the texture is lighter, the drying can be speeded along.

In the second photo, you see some of the ways I get mud to dry more quickly. On the counter* you see two box fans, and on the floor is a much stronger fan. On the counter is also a space heater. Hot air in the room absorbs moisture, sucking it out of the wet smoothing compound. I let the room heat up, and then I have to open the door and let the moist air out – over and over again.

The yellow objet on the floor is a heat gun. A heat gun acts like a hair dryer on steroids, and can get small stubborn areas to dry pretty quickly.

A few other things help speed drying … Walls coated with flat paint will dry more quickly than with glossy paint. And having the air conditioning and / or heat cranking away will help, because, while regulating the temperature, these climate-control systems also pull humidity out of the air. I also like to turn the HVAC system’s fan from “Auto” to “On,” so that air is circulating continuously, which also pulls humidity out of the air and helps the walls to dry.

*I normally keep a dropcloth on the vanity counter. But the vibrating fans can cause the dropcloths to slip, and you don’t want anything crashing down on the homeowner’s countertop. I do have lengths of self-grip shelf liner that help keep the fans from moving around too much.

Wall Prep – Missing Chair Rail and Stain Repair

March 31, 2019


What an unexpected surprise I got when I arrived at work to discover that the chair rail in this entry had been removed (top photo). Not only did I need to figure how to get enough paper to cover the additional wallspace, but I needed to smooth over the damaged wall area where the molding had been torn off. (See previous post)
I skim-floated the wall and sanded smooth. It looked great. But brown coloring from the torn Sheetrock had worked its way through the smoothing compound (second photo). Torn drywall is not something that I would normally worry about bleeding through wallpaper (you are concerned mostly with things like grease, ink, water, tobacco, rust, and the like), but this stuff was 60 years old, so who knows what its properties and characteristics were back then? And besides, it had already worked its way through a layer of joint compound – in just one night! No sense in taking the chance that it might bleed through this nearly-white grasscloth natural fiber wallpaper.

The Gardz penetrating primer / sealer (not pictured) I planned to use on the wall would be fine to hang wallpaper on, but could not guarantee that that brown stain would not work its way through the primer and through the wallpaper.

I applied the Gardz, because it’s a great penetrating substance that seals new smoothing compound, and also provides a good surface for hanging wallpaper on. Once that was dry, I followed that with a coat of KILZ Original, an excellent oil-base stain-blocker. But wallpaper paste will not stick to the new KILZ formula (required in order to comply with current EPA requirements.

A little 3″ width around the lower center of the room with wallpaper not sticking tightly to it probably would not be problematic. But you never know, and I didn’t want a “hula hoop” of delaminated wallpaper circling the room. So once the KILZ was dry, I followed up with a coat of a wallpaper-specific primer, Romans Ultra Prime Pro 977.

Now the room is ready for wallpaper, without fear of a band of tan bleeding through the new surface.