Unfortunately your renovation involves waterproofing and this indicates that it cannot be classified as a ‘minor’ renovation. Has anyone in your building undertaken this type of renovation previously, and if so can you ask to see their by-law? Perhaps you can tweak it and create your own by-law along similar lines.
Also, there may be generic “off the shelf” by-laws that you could purchase for a cheaper cost then getting an individual by-law drafted. Solicitors, however, generally frown upon these types of generic by-laws.