US law sounds pretty much the same. It is not a violation of copyright if the copy falls under "fair use" -- which is a slippery term, but mostly means what it sounds like. See: http://fairuse.stanford.edu/Copyright_and_Fair_Use_Overview/chapter9/index.html for a more detailed summary of "fair use" under US Federal Copyright law.
Apart from the law, common sense should prevail. Your common sense tells you that copying 15 pages out of a pattern book "feels" different than photocopying 15 pages out of a novel. This is probably because it seems to you like it makes up a more substantial part of the whole copyrighted work than the "same" amount of another kind of work.
But this whole thing is rather fuzzy. If I photocopy out of a pattern book, the title page, the introductory material, the glossary, it "feels" different than if I copy a pattern straight from the book -- even though both contain copyrighted material and someone else's work -- however, that does not mean that photocopying one pattern from a book is not fair use either.
I feel like if I check the pattern book out of the library and make the pattern at home, then return the book, in a way I have also "copied" the pattern -- it is within the finished product I crafted and I can refer to that item itself without the book to use the same stitches or techniques later. But I think no one would consider that a violation of copyright law.
I have also photocopied patterns from books in the library to the extent that it did "feel" like it crossed the line of fair use (about 20 pages), but in that case it was copied from a book I had previously purchased and own, but was in storage in another city, so more convenient to copy from the library than to travel to the other city and retrieve my own copy.
I still say go with common sense, but also think about actually checking the book out of the library if that is possible. If the library knows that those sorts of books circulate they might be more likely to purchase more craft books in the future, helping the pattern makers, publishers, and library patrons.