I’m a landscape contractor in NorCal and like most of you don’t want to pay for it if I can do it myself. So I stripped 70 years of wallpaper and paint off the walls and found the cracks I expected to and some I didn’t. Love some advice on how to patch cracks in 70 year old plaster and wooden lathe that is extremely hard and is reinforced with what appears to be animal hair. My initital thoughts were to create 2″ depressions centered on the crack for fiberglass tape and then mud over it with plaster compound.
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I chip out the areas on both sides of the cracks with a small hatchet (shingle hatchet works well). Use lots of quick chops into the surface to chip away the surface plaster and any real soft stuff beneath. Then clean up with a shop vac and paint all the cracks with a rewettable acrylic bonding agent. These are sometimes called adhesion promoters and are basically a glue like elmers that will rewet when you apply the plaster and glue it securely to the old plaster. Now tape everything with fiberglass mesh tape. If you can get to a plaster supplier they will have a version that is wider than the standard drywall stuff and that wiould be preferred. Any really deep holes need to have pieces of wire lath wedged in to reinforce the fill. The deep areas (3'4" plus) get partially filled with Structo-lite or Gypso-lite (mix a bit of alum into the mix water for these products to make them set). Then use drywall mud to fill in the surface areas. The old hard 90 minute durabond is ideal but use easy sand if that's all you can get. In any case, use the easy-sand for the topcoats. Don't use the ready mixed mud. When you are chipping out you will find more cracks below the surface and any serious looking ones should also be followed out and chipped open. the base coats are always softer than the topcoats so just remove the really powdery stuff, when you get to the firmer areas stop chipping, or you will have to replaster the whole house.
I'd caution you on any pounding to make a depression or to remove loose plaster. You very well could end up loosening the keying in other areas around the cracks. The hatchet idea can work, but again you should work with the crack and not be hacking directly at it. A stiff mud knife or the hatchet end or even the corner of your claw hammer can pull off the loose stuff or grind a slot. I use paper tape, but that's just a preference. Setting type compounds, not topping, will have more adhesive in the mix and the use of a plaster weld/glue is a good idea. Be careful with your use of regular durabond, it sands very hard. If the cracks are minor, you might pick up the april 2003 issue of Old House Journal where it explains a no tape style repair on the texture found in some old plaster jobs. Best of luck
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Remodeling Contractor just outside the Glass City.
http://www.quittintime.com/
Mario Rodriguez had an article in FHB (or FWW?) a few years ago in which he described a technique involving WIDE FG mesh. It comes in 1 yard rolls. Basically you cover the entire wall with this stuff to stabilize the crumbling plaster and then skim a couple of coats of DW compound strengthened with mason's sand. You end up with a finish that resembles real plaster. Or so he says. Has anyone tried this?
I've done it on some old houses, minus the sand, and have found it to work well. The stuff is called Permaglas mesh, and is available thru Sherwin-Williams, though you may have to convince them to find how to order it. It does take some care to lay it down flat - a second pair of hands would be nice.
Hope this helps. Rich.
re - The stuff is called Permaglas mesh, and is
available thru Sherwin-Williams, though you may have to convince them to find how to order it.
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Yes, indeed.
My search for the stuff led me to the local Sherwin-Williams dealer who had to special order the roll for me.
It was around $25 plus another $5 for getting it to the store.
Didn't take much explaining what I was looking for.
I've done the living room ceiling in my home 3 times. The first 2 times I did it with everwidening gaps patched as lovingly as possible then stippled with a brush to match 80 years worth of paint coverage. They always open up with the spackle I used. 3 weeks and a room full of dust yielding 2 years worth of crack free surface.
The last time I used a professional. 8 years and running. About $600 for a 14x24 ceiling.
Possibly you are better with a trowel and sander than I am. Lets hope.
If you have as many cracks as sounds like, you will be mudding a mile of patches. 1/4" SR over the whole area has been faster for us. Lot less cracks showing up later.
1/4" parting stock at the doors and longer elec cover plate screws.