Can "very" be used as a multiplier? For instance: A house, a big house, a very big house, a very very big house meaning a bigger house than a very big house and so on.
You could use 'very' to give an indication about its comparative size to an average house, but as mentioned by @Mazz, this becomes boring really quickly if you're trying to write something you want people to read.
Using other adverbs as proposed by Mazz is an option, however it's better to use another adjective all together for readability and a more engaging text.
Smaller house: The tiny house (Instead of 'the very small house')
Small house: The small house
Normal house: The house
big house: The big house
bigger house: The huge house (instead of 'the very large house')
I hope this example helps you to deal with the use of 'very' and perhaps offers you some alternatives on what words to use instead of it. This is applicable for many adjectives, especially those that indicate size or some order of magnitude as with your house example provided in the question.
You can certainly do that, but be warned that it would be received as a very informal style of speech. One might say that the number of "very"s you place in front of a word will also modify the informality of the sentence. :)
If you don't want to change the adjective, as Hyfnae suggested (quite sensibly), you could also amplify the implied size by choosing a word that has a larger impact than "very", e.g.:
"It was a very large house."
"It was a remarkably large house."
"It was a terrifically large house."
"It was a strikingly large house."
"It was an extremely large house."
"It was an exceedingly large house."
"It was an unbelievably large house."
"It was an inordinately large house."
"It was an astronomically large house."
This would also allow you to imply more than just the size, as many of these words carry extra meanings, e.g. "inordinately" indicates not just that it's very large, but also that the speaker considers it to be too large.
You could also reduce the impact a little, while still increasing the impact vs. just saying it was a large house:
"It was an unusually large house."
"It was quite a large house."