Posts Tagged ‘tension’

Potential Trouble Brewing

July 7, 2019


What you see here is a bit of rubbery latex paint and texture that has peeled away from the wall in this powder room. The surface underneath it felt gritty and dusty and porous. I had the feeling that if I had tried, I could have peeled all the paint off the wall.

This is not good.

This paint is probably peeling because of a combination of poor quality materials (cheap paint), improperly prepared surface (inappropriate or no primer, not removing dust from the wall, incompatible coatings (latex over oil based, not sanding or deglossing a gloss paint before repainting), climate fluctuations (humidity, temperature), stress on the wall (pulling off a piece of tape), or more.

All this is not so bad under paint, because paint just kinda sits there on the surface. But wallpaper actually puts stress on the surface beneath it, as it dries and pulls taught. Over time, fluctuations in humidity and temperature can exacerbate that, causing the paper to expand and contract ever so slightly, and then put tension on the wall where the seams fall.

This can result in not just the seams coming loose, but in the various layers inside the wall actually delaminating and coming apart from themselves.

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Trouble Brewing? Paint Not Adhering to Wall

June 26, 2019


Top photo: A small circle of paint had been pulled away from the wall. When I picked at it, I was able to easily detach more paint.

Second photo: When I removed the light switch plate, some paint had stuck to it, and pulling the switch plate off the wall took some of the paint underneath along with it.

The exposed wall underneath the paint was gritty and dusty. I could not tell if it was a layer of old paint, drywall, dust, residue from ancient wallpaper paste, or other. I had the feeling that if I had tried, I could have peeled all the paint off the dusty subsurface.

This is not good.

This is an old house, and many layers of paint and other treatments have been added to the walls over the decades (100 years!). Many of these substances are not compatible with each other, and especially not if the walls were not prepped properly before applying another coat of paint.

Latex paint won’t stick to oil based paint. New paint won’t stick to a glossy paint. Nothing sticks to a dusty surface.

All these various materials will adhere to one another – for a while. But when a stressor is added to the formula, there is the potential for the layers to delaminate (come apart). That’s what happened in the two areas above, when a bit of a tug was all it took to peel several layers of paint away from the wall.

The issue here is that wallpaper comes with its own stressors. Wallpaper gets wet when it’s pasted, expands a bit, and then when the paste dries, the paper shrinks a tad and puts tension on the walls. Over time, with changes in temperature and humidity, foundations shifting, and just plain old passage of time, this tension could cause the paint to give way from the walls – this usually manifests at along a seam.

I use a wallpaper-specific primer, and among its attributes is the ability to withstand this type of tension.

Let’s hope that over the years, the many layers of paint, the new coat of primer, and the wallpaper all work together to stay nice and tight to the wall.

Note: If I had known about the wall condition earlier, and if the homeowners’ budget had allowed, a liner would have been a good option in this case. A liner is a special type of paper that is applied to the primed wall the day before the paper goes up. It serves several purposes, but one is to distribute tension across the wall. Because the seams of the liner do not line up with the seams of the wallpaper, drying and shrinking wallpaper puts tension on the liner, and not onto the unstable wall itself, thus pretty well eliminating the chance that the wallpaper seams could cause the wall to delaminate.

The downside is that using a liner adds an extra day (or more) of labor, plus the cost of material.

Rubbery, Problematic Smoothing Compound

June 15, 2018


I was stripping wallpaper by peeling off the top vinyl layer and then soaking the paper backing to reactivate the paste so the paper could be removed from the wall – and ran into this.

It looks like the previous installer smoothed the wall (which is good), but used a latex spackling compound instead of the more typical joint compound. The latex became wet from the water I was using to soak off the wallpaper, and began to pull away from the wall.

This is all bad, because it leaves a bumpy mess on the wall that will show through the new paper. But worse is that it is an unstable surface for the new paper to try to hold on to. When wallpaper paste dries, the paper shrinks and puts tension on the surface below, particularly the seams. If the surface is not solid, the layers can actually come apart (delaminate) resulting in curled or gapping seams.

This is not “loose paper,” and cannot simply be glued back down. The different layers inside the wall are actually coming apart, and will require a lot of work to make the wall sound again.

Once the paper was off and the wall was good and dry, the layers seemed to adhere to each other better, and the wall felt more solid. The way I treated it was to roll on a coat of Gardz, which is a penetrating sealer that binds things together. It did a good job. Then I skim-floated over that with joint compound, which, when sanded, would leave a nice, smooth surface.

One more coat of Gardz on top of that, and the wall was sound and ready for wallpaper.

Another Reason to Not Let the Contractor Prep the Walls for Paper

May 10, 2018


Folks, please do NOT let your contractor or painter “prep the walls for wallpaper.” They simply don’t know how to remove wallpaper properly, and they don’t know what is required to prepare the surface for the new paper. Do a Search here (upper right corner) for more examples.

In this case, “I know that he removed the old paper, because I saw piles of it on the floor,” said the homeowner. But this photo proves that he didn’t. Nor did he bother to remove the towel bar, because when it was removed later, you can see the old wallpaper still under it.

I put the original wallpaper up back in the ’90’s, so I know that, with my good primer underneath, with a bucket of warm water and a little time, that paper would have come off easily and left the wall in perfect condition for new paper.

Instead of properly removing the old paper, this contractor skim-floated over it. That’s the thick white stuff you see in the photo. After sanding the wall smooth (which he did OK in most of the room, but, as usual, did a less than stellar job in corners and around moldings and door trim), he should have removed dust from the walls with a damp sponge – but virtually no contractor bothers with this step.

Removing dust is crucial, because if dust is left on the wall, it may hold up OK under paint, but when wallpaper is applied on top of it, when the paste dries, the paper shrinks a tad and puts torque / tension on the wall. When the walls are dusty, there is the potential for the surfaces to delaminate (come apart), leaving you with seams that gap and curl back. These cannot be glued back down, because the surface underneath is unstable and provides nothing for the paste to adhere to.

So next the contractor primed the walls. There was no mention of what primer he used. But I can tell you that primers formulated for paint are not advisable under wallpaper. PVA-based primers are commonly used under paint; they are designed to keep the paint from flashing. But they are soft and don’t provide a stable surface for wallpaper.

Primers formulated for wallpaper are designed to 1.) adhere to the underlying surface, 2.) provide a “crystalized” surface that the wallpaper paste can bite into and grab ahold of, 3.) provide a surface with “slip,” which will ease installation of the new wallpaper, 4.) allow for easier removal of the wallpaper later, with minimal damage to the wall, and 5.) withstand the torque / tension created by the drying wallpaper.

Ask a contractor or painter if he knows any of the information in the paragraph above. You will receive a blank stare.

All more reasons to NOT let the contractor prep the walls for paint.