Expansion joints

[Michael Baughman C.P.]

I need to fill two long expansion joints for a mural install. The two joints are 2" high 1/2" deep 24.5 feet long. The two murals are one panel each 14’ high by 24.5’ long so the is no concern about seams over the joints. I need a system of filling the joints for about 6 months till the display wall is changed again.

My 1st thought was cover with tape shoot in expanding foam. Cut off any extra foam once dry then prime. This would be difficult to remove later to return the wall to the existing condition.

2nd thought is precut foam that is ½” thick in 2” wide strips attach with thin double sided tape and cover with 6” fiberglass drywall tape.

What are you thoughts?
I need something so the canvas does not pull into the joint or show any high spots from the filling. I have to be able to remove it cleanly at a later date TBD.
Keep in mind this is a temporary install that has to look prefect for 6 months or more.

[Jim Seymour]

DAP Tex Multi-Purpose Foam Sealant or Dow Door and Window Foam canned insulation may work. They are latex based and do not over expand. Fill the joint and when set(next day) remove any excess by shaving wih a wallpaper scraper or a sharp, thin broad knife. As for prime...a thin coat of paste should work. The latex foams are a lot softer and less adhesive than some of the other insulating foams. Removal-the DAP at least will come off bare drywall without damage merely by rubbing it. A vinyl sweep or scrub brush will hasten things along. Both should be at Lowes or Home Depot and hardware stores. About $6/can. Give it a test first.
Jim

[ProWallGuy]

Michael, I'd probably opt for the styrofoam scenario. Cut it slightly large, and stuff it in. Shave off what sticks out the top. Use a 1"-2" brush, and seal the top of the foam with Gardz. Then run a quick, thin coat of mud over it. When its time for removal, the mud will wash off easily, and pull the styrofoam out.
My 2 cents.

[Lillian]

Michael,
We used Bondo for the expansion joints on the Cruise Ship. Got it at the Auto Shop. It ruined the tools as far as trying to keep them clean. Just use old tools or better yet, plastic. It will stay tight and will not flex out with any movement. It is easy to find and quick to mix together. The only negative for me was the awful odor.
Good Luck
Lillian

[Bill Archibald]

Michael,

My first concern was the word "expansion joint". The purpose of which is to allow expansion and contraction of two plates without causing buckling or cracking. If a mural bridged this expansion joint (no matter how it was filled), wouldn't the natural expansion and contraction cause havoc with the mural?

I point out this observation with the full expectation that this was already considered and made a non issue - but I did feel compelled to speak to the obvious

If this issue has already been negated, I like the styrofoam covered with the mesh tape (or even paper tape) and a coat of mud. Your expanding foam has a very aggressive adhesive and would be problematic to remove.

OR, cut strips of 1/2 inch thick sheet rock and lay it with your double stick tape. The reason I say 1/2 inch sheet rock is because it would be easier and more exacting.

[Lee Epstein]

O.K. here is my 2 cents worth. You're filling them for a short time and have to remove it cleanly? They still have to expand so plaster is out. Taping will still crinkle(?) How about applying vasoline to the entire length of the expansion joint. Then fill with latex caulking. The caulk can still expand and contract and hopefully the vasoline will let you remove the caulk at a later date. Stupider things have worked.

[HangingInThere]

I would also agree with Tim regarding your styrofoam application with mesh and mud. I would caution over using Expanding or non-expanding foam as there is no solvent that will affect it once it has cured.

After the skim coat I would suggest priming with thinned adhesive...perhaps a couple of coats. You would want it to penetrate a bit into the drywall mud and form a continuous film over it. Thus, if enough moisture were added, it would soften and the mud and adhesive could then be removed. It would also provide enough hold out for the install.

As also pointed out, the purpose of the expansion joints is to allow movement without compromising structural integrity. They may or may not flex on you during the time that your finished product is displayed. We assume that the client knows that...

[gadams]

Yea I vote for your 2nd thought or Tim's idea.

[Gary Lucas]

The solution may be as simple as 3" duct tape, primed and with a thin mud finish.

Gary

[HangingInThere]

Interesting idea Gary... Perhaps, rather than regular duct-tape, one might want to consider the silver foil duct-tape. It also adheres well to most surfaces, is extrememly durable, could provide a more taut surface if placed properly, would be unaffected by moisture, and ultra thin for mudding...