In one of my rental properties the front foyer has VCT (vinyl composite tile). These were installed probably 30 or more years ago directly (?) on top of the original 120 yr old fir tongue and groove flooring. The tile is old and I need to do something with it. On the most heavily traveled area, the joints in the fir floor have telegraphed up thru the VCT, cracking it. I'm wondering if the same thing will happen again if I put another layer of VCT on top of the existing. Or, will that additional layer of old VCT have a moderating effect on the new VCT?
I know I could put thin plywood on top the tile before installing the VCT, but this would involve removing 4 doors in the foyer and trimming the bottoms. It wouldn't be a big deal except the front door is huge, heavy and hasn't been disturbed in probably 100 years and I don't want to induce any bad mojo into it.
One layer of VCT is thin enough that I won't have to cut any doors. Current VCT is also about 30-20% thicker than the stuff that was installed long ago.
Opinions?

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13