Plaster - Advice on patching where lath is missing

[historicalwork]

Hi, I wanted to ask what most of you with plaster experience would do when encountering areas where the lath is missing. Please see the picture below. I don't have any spare pieces of lath. My impulse is to take a couple small / thin piece of wood strips, get them behind the current lath, and then screw them in to hold in place. Then use that as the base for the easy sand (first coat). With such a small area, do I need to worry about the new easy sand being keyed in between the new strips? Just curious what others would do in these situations. I want to try and do it right the first time. Btw, as noted in my previous post on this room, it seems like the wire in there is from old knob/tube. I'm of course going to double check nothing is live - I'm not aware of any active KT in the house but I'll be checking.

[Willa]

With a small area like that, you could patch in a piece of drywall, screwed to the adjacent lath. Then I would skim coat over the area until it is level with the rest of the wall. This will take a couple of coats or more to get the edges feathered enough.

(First remove any loose or crumbling bits on the periphery.)

It was a revelation (to me) to discover that there is 1/4" and 3/8" drywall*. The plaster in my house is thin. The thin drywall made it possible to patch in a troubled area to make it nearly flush with the wall. Once properly skim coated and sanded the borders of the patch become invisible. I do not feel that repairs like this compromise the integrity of an old home or plaster walls.

There may be others here who can better advise about lath repair, etc.

Joint compound is okay to use for repairs like this. True lime plaster has a very long curing time. Don't use Plaster of Paris as it dries too hard.

* Staff at a big box store told me no such thing existed, despite it being on their website. However - this non-existent drywall was available at a smaller building materials store a few blocks away.

[historicalwork]

Thank you, Willa. Well, I started taking a closer look at things and a lot of the plaster was loose - could feel it move and some of it just fell off. I took a utility knife and scored some areas to where I thought it felt firmer. I'm suddenly questioning taking down the closets! :/ It's clear to me that all the hammering they did for the framing when putting in the closet probably did a number on the plaster on that wall. Plus, there are places along the baseboard where they cut out baseboard molding and cut into the lath - creating more problems. I need to look at other spots on the wall but I'm starting to wonder if this is beyond my ability to repair with quick set compound (easy sand) and if I should consider using drywall. And then I need to decided if I patch areas with drywall or just laminate with 1/4 and deal with the lose of reveal at the door trim.

[Gothichome]

Historicalwork, it’s never easy or simple fix is it! Corcetiere or one of the smart folks might have a better idea, but here’s my thoughts.
Depending on how thick your plaster is, probably on the thick side of 3/8th, you could lay a sheet in as a filler and use drywall compound to bring it level or maybe a touch prowd. Feather it way out on to plaster. For the smaller hole I would suggest using a mesh product available at most hardware stores, usually sold as drywall patching mesh. Using drywall compound, set the mesh in place onto the existing lathing, let dry and slowly build it up to leval and once again feather way out from the repair.
If you want to work in real plaster all the fixes could be done just subbing for the drywall compound.
If you are really worried about the whole wall, Corcetiere and others have used the Big Wally’s method with great results.

[Willa]

Don't despair ! The bad areas look redeemable.

Just patch in what has come loose, where the lath is exposed. Don't feel you need to cover the entire with drywall. (If you were doing this you would have to remove the rest of the plaster or use furring strips to level the areas where there is no plaster. IMO there is no good reason to remove plaster that remains sound.)

1/4" drywall attached directly to the lath, then skimmed over should not bury the profile of the door trim.

I managed to scare up some antique baseboards and trim on Kijiji. They weren't a 100% match for what was here, but were certainly better than what I could buy new.

How is the rest of the wall ? Do you know about plaster repairs (IF needed) using plaster washers ?

A house that is several decades+ takes some wear and tear. At least in old houses things are made so they can be fixed v.s. junked.

See Jane Drill has some excellent videos. Here are a couple about skim coating and repairing a hole in drywall. What she suggests is also applicable to plaster walls missing lath:

http://seejanedrill.com/repair-drywall/

http://seejanedrill.com/plaster-skim-coat/

[nhguy]

I usually plaster washer the area surrounding in need of repair. Screwing in a piece of drywall or buying some lath at a lumber yard and screw it in place. When I use drywall generally I brush or roll on some thinned Elmers Glue as a bonding agent. This might be overkill, but it's the way I am. I use Durabond 90 for my plaster as it dries harder than the stuff in a bucket. You can get the easy sand type too, also Durabond. Both will do the job very well.

[heartwood]

I am NOT a plaster person but.......what about the galvanized metal mesh that is used in more modern plaster applications...can't you screw that onto existing lath? I support the plaster washers for repair...

I've heard positive responses to this product: http://www.plastermagic.com/

...jade

[historicalwork]

First, thanks to everyone for the quick and helpful advice and encouragement. I hate feeling a bit put off by plaster - I've done DYI framing, drywall and other light construction. But the plaster is just something I've avoided. This time I have more time versus being rushed. So, I went back in the room and checked the whole wall. I scored around areas that were clearly loose and pulled off the plaster. Where I thought it seemed OK I added some plaster washers. I've cleaned out all the keys between the lath and vacuumed. I broke up some larger shims and drilled/screwed them in a couple places to reinforce the lath.

After going through this, it's clear when they built the closet - I guess maybe 20-30 years ago - they did a number on the plaster. And because this wall was essentially on the insight of that added closet - it wasn't an issue. I see they also cut the trim piece on top of the original closet - I need to replace that along with the cap. And there is plaster that just pulled off up there.

The one thing that I'm still not clear about is how to gauge the thickness of the plaster in these lager areas. I did go back and watch all the videos I could find on youtube. For example, as I look along the baseboard (facing the baseboard), the plaster thickness is thinner to the left (~ 3/8") and gets thicker to the right (~1/2+). At the bottom - near the floor - do you just eye it for the right thickness as you build up the layers? I'm thinking I need a fairly straight line of plaster for when I put a piece of baseboard trim and basecamp in (I really it won't be perfect). Where I am coming up to existing plaster I didn't remove, clearly I have a guide for thickness. But as I move towards the floor or as I think about the middle areas, I guess you just get the hang of putting it on right? Maybe I'm over thinking it and it's one of those things you just figure out as you go.

I picked up some easy sand 90 today. I assume I can use that for all coast - first coat on the lath and then up through the finish coast? It turns out I got a gallon of plaster weld some time ago. That Kirk Giordano guy on youtube (who I love watching) seems to recommend it. Lastly, if I remember from having a guy help us finish the walls in another room, he just used regular drywall mud for the smaller imperfections on the wall. Or, would others recommend using easy sand for that as well? I guess the drywall mud has a nicer finished consistency - at least that's what I've read..

Every project sure is a learning experience...

[Willa]

The carpenter I used had 6" squares of different thicknesses of plywood that he would fit against the lath to judge what depth of drywall I needed.

Frankly I have terrible plaster in my house. The basecoat is inferior (crumbling, lots of broken keys) and the final skim coat of plaster on the top is very thin. The actual thickness varied on walls from between 1/4" - 3/8" - often within a few inches distance.

If you use the thinner drywall to patch, you will need to build up layers if there is variance in the actual thickness of your plaster. If the drywall patch is a little thick you will need to feather out a considerable distance to blend this in with the wall.

When I used plaster washers I used mesh tape over the washers to better hold the joint compound. There is a lightweight joint compound that is sold dry - it has lightweight fibres as a filler. This was useful when I had to fill in deeper areas as I could mix it a little thicker/stiffer to build up. A few thinner layers are better than a really thick layer, as a thick layer tends to crack.

Every simgle time I have done plaster repairs I feel very demoralized by how terrible the first layer of patching looks. However - when I watched videos of pros doing plaster repairs it also looks terrible at first. The trick I think is to build up several thin layers that get progressively wider (ie feathered). There comes a time when suddenly your repair just looks like a wall again. I am certainly not a plasterer by trade - so I felt no shame about using mesh tape or sanding near the end.

There certainly ARE pros who can do miraculously smooth plaster that needs no sanding, and their technique looks effortless and graceful. I'm not them though, so a repaired wall that is smooth but not perfectly flat is fine by me.

[Kashka-Kat]

For the holes, I just staple on metal mesh (aka metal lath) to the wood and then plaster over it.

Drywall patch for the big areas of missing plaster that span two or more studs (you want to attach drywall to studs, not lath - if its a big patch there can be a lot of weight so it needs to be screwed on securely). In choosing drywall thickness, err on the side of too thin - you can always build it up slightly if you have to. The fact that your original plaster is not exact same thickness throughout means there can be some slight variation in your repairs and no one will notice.

I would not use easy sand, except for over the drywall patch and/or the topmost layer over plaster which you can then easily sand smooth. Its too soft for filling large or deep holes. If you have many wide gaps between drywall patch and the old original plaster, then buy actual 2 coat plaster from a bldg supply store (big box wont have it). Be sure to use a bonding agent liberally on all surfaces - edges of old plaster, the wood lath, etc. - to help adhere the new plaster to the old surfaces. Before painting on the bonding agent, you can take a scrub brush and warm plain water and wash out the dust and dirt - this also wets the old wood + plaster - which, along with the bonding agent, prevents the new plaster from drying out too quickly and cracking.

Have fun - Ive found that its the kind of low tech home repair task that a homeowner can learn to do well - and save considerable money vs. hiring a plasterer or drywaller.

Whatever you do, dont laminate thin drywall over existing plaster and butt it up against the trim - yuck. That is a sure way to ruin your walls. Sorry if I offend anyone, but it is UGLY and next to impossible to remove/repair.