We bore injection holes with a 1/4″ carbide drill bit. If you are only reattaching plaster, plan for injection holes every 3″ to 4″, no more than 6″ apart.

If you have an infill area that needs reattachment at its edges, mark for injection sites 1 1/2″ to 2″ back from the edges. Once you have a solid fix on one lath, assume that the rest of the lathing is 1 1/2″ to 2″ wide and spaced approximately 1/4″ to 1/2″ apart. Sometimes, if the plaster is not too thick, you can stand back and look for ghosts or shadows of the lath showing through the finish coat. In a reattachment-only repair, however, finding lath is basically hunt-and-peck. If you have removed any plaster, or dug out a crack for repair, then you can see the positions of the lath. The holes you bore to inject the adhesive must be directly beneath the wood lath-not the spaces between the lath-so that the adhesive can bond to something solid. Mark with a lumber crayon or pencil a pen will bleed through your paint later on. (We call this the domino-delamination effect.) To control this tendency we recommend carefully marking out your repair plan, then removing any areas with a sharp utility knife. Removing areas of damaged plaster-particularly in a ceiling-will encourage more plaster to come down, especially if you use a chisel-edged tool. Holding a vacuum nozzle on the drill bit helps suck the 1/4″ injection holes clear of dust. Plaster that is soft and crumbly will not hold up during the pushing and drilling and has to be removed as well. Often we find that the worst part of the ceiling has too much debris, and we have to remove this section, reattach the edges, then infill the lost parts with new plaster. Unless you can vacuum out all this debris from above, reattachment is probably not an option. If the plaster sags 1/2″ to 1″ from the lath, there is often too much debris (broken keys, years of silt) between the plaster and lath for success. If the separation is slight-say, between 1/4″ and 1/2″-good reattachment is likely because the plaster will usually push back into place solid and flat against the lath. Instead, just gently encourage the plaster with the flat of your hand. Do not force it back into place or more plaster may break.

If there are broken keys or debris in the way, the plaster will resist seating, and it will feel and sound “crunchy” akin to breaking eggshells or crushing popcorn. Hopefully, you will feel it move back into place like a jigsaw puzzle piece sliding into its own unique spot. Gently push on the surface and judge the amount of play between plaster and lath. Stained cracks and suspicious shadows-the telltale signs of a delaminating plaster ceiling.Īfter correcting whatever problem made the ceiling loose in the first place (leaky roof, structural alterations), the first step is to assess how far the ceiling has pulled away. With these methods and good tool skills it’s possible to restore the integrity of plaster ceilings for many more years of service. Though variations of this technique are not new–texts from the 1920s recommend liquid sulfur as an adhesive–we use modern materials that are easy to handle and inflict minimal damage to sound plaster. We have successfully reattached many old ceilings by injecting adhesive between the plaster and lath where the keys (anchors) have broken away over time. The good news is, it’s possible to repair and rescue plaster ceilings from further damage.

Plasterboard ceiling