It should be Mr. and Mrs. Smith's house.
It is correct to say "my father's house" with an apostrophe to show possession.
The house belongs to Dave. It should be Dave's house.
The use of apostrophes in last names is no different from their use in any other word. If you are referring to a house to belong to a family named "Smith," the sign would read "The Future Home of the Smiths." No apostrophe: it is merely a plural noun. If the phrase were "The Smiths' Home," that apostrophe is correct because you're using the plural possessive: the house belongs to more than one Smith. People who write things like "The Smith's" are incorrect (as was the previous answer to this question). General Point If you indicate possession by using of you musn't also use 's or s'.
The Smiths in this case would simply be the plural of Smith. So there would be NO apostrophe. Plural, meaning both persons as a married couple: Please meet the Smiths. The Smiths were away when their house was robbed. Plural Singular The robber took the Smith's television. The Smith's home owners policy covered the theft. IF you had a large meeting for all families named Smith, the simple plural would also be Smiths. However, for plural possessive, you'd first have Smiths with an apostrophe added, like this: All the Smiths from Washington, DC attended a city-wide picnic. While there, all the Smiths' (s apostrophe) cars were vandalized. The picnic's promoters, the Browns, were doubly embarrassed; none of the Browns' (s apostrophe) cars were damaged. If you have more than one person of a surname, just add 's'-- unless the name ends in s. (Smiths) If you have more than one person of a surname, so you add s, to make it possessive, add apostrophe after the plural s. (Smiths' coats... Smiths' cars... Smiths' cellphones...)
The apostrophe floating on its own at the end of a word is not usually correct in the singular form, and it is certainly incorrect in "house' directions". Write instead "house directions". If the plural is required, the apostrophe at the end of a word is correct. For example, when seeking the directions to a group of houses, it is correct (though somewhat awkward) to write houses' directions.
The house sign should say "The Smiths" to indicate that the house belongs to the Smith family. Using "The Smith's" would be incorrect, as it implies possession or belonging to a single individual named Smith.
at her house
For plural proper nouns ending in "h," you can add an apostrophe after the "s" to make it possessive. For example, "The Smiths' house" would show that the house belongs to the Smith family.
An apostrophe is used to show possession: the house belongs to the Robinsons; therefore, it is the Robinsons's house. Our house (or ours - no apostrophe) is on Randolph Drive. Randolph is the name of the drive; it doesn't belong to anybody in this sentence. Of course, the sentence should be:"The Robinsons' house is on Spring Street but ours is on Randolph Drive" as "ours" is a possessive but is an exception. Unfortunately the Wiki spell checker doesn't know the correct usage either. Sigh.
The plural possessive form of "smith" is "smiths'".
When a name ends with an s, you can use an apostrophe followed by an s ('s) to indicate possession. For example, "Charles's book" or "James's car." However, if the name is plural and already ends with an s, you can just use an apostrophe (') to show possession, like "the girls' toys" or "the Smiths' house."
There are two accepted forms for possessive singular nouns ending in s:Add an apostrophe (') after the existing s at the end of the word: boss'Add an apostrophe s ('s) after the existing s at the end of the word: boss'sExamples:I dropped the file off at the boss' house.I dropped the file off at the boss's house.