@Peggy Wilson: You're treating that initialism (acronym) as a name, but while this is cute, it's really not correct. Therefore, your example should very clearly be the "LARAS House" (note the prefixing "the", as well). If it was a "…Facility", it would be the "LARAF House".

And, back on the original topic: The only time an apostrophe should be used before an "s" to indicate plurality, would be if the result could be otherwise misconstrued.

A (poor) example: If I'm trying to indicate the plural of the ninth letter of the alphabet, I cannot simply indicate "is", since this would be confused with the 3rd-person singular present form of "be". Therefore: "The sign kit included several dozen lower-case tiles, six of which were i's"

But, again, this is an exception. Apostrophes are used to indicate possession; simply adding an "s" is the primary method of indicating plurality.