takai

高い ビル
高くない ビル
高かった ビル
高くなかった ビル

That was

pricey or expensive building
not expensive building
was expensive building
was not expensive building

is that correct?
lotsa ka's in there...

when you combine takai and biru (sorry, no Japanese support on this computer), takai means tall, not expensive.

Also, when using the past tense as a noun-modifying clause, such as "takakatta biru," it sounds like the building WAS tall, but is now not, perhaps because it shrank or fell over. Same with the negative past tense; it's as if the building used to be (whatever adjective in past tense), but is no longer that way. Generally, we don't use the past tense in noun-modifiers like this. Also, you don't need to put spaces between words in Japanese.

But grammatically it's conjugated correctly.

Technically speaking, as い adjective are actually pseudo verbs, you would get the following:

高い ビル = a building that is tall
高くない ビル = a building that is not tall
高かった ビル = a building that was tall
高くなかった ビル = a building that wasn't tall

thanks i looked it up and i thought it meant tall like a tall price, idk

i think i get it, i just wanted to make sure i was conjugating it right.

thanks guys. :]

takai can mean either tall or expensive, but you have to be careful about what you are describing. It's like saying "that price is pretty steep" vs "that hill is pretty steep." If you want to eliminate any misunderstanding, just be more specific.