Well depending on where you are and how high above the water you are you might be surprised at some of the restrictions that you will have on the design of the building.
One of the big restrictions is the distance your current cottage is from the high water mark.
What is the high water mark? The high water mark is an elevation that building departments use that assumes the highest point the water has risen in the body of water that your cottage is located on. That level could have happened last year or 100 years ago.
The point of the high water mark is that they want all structures built behind that mark so that if the water was to rise then it would not swamp the house. (as long as it never rises above the high water mark that is).
New builds are affected because you have to build far enough back to be behind it or build up to end up above in low lying areas.
But with an addition they can't make you move your whole cottage back or out of the way and so they can't make you move your addition up or away. What they can do is have certain restrictions on how you design the addition and the openings in that addition.
One of the big ones is that you cannot have any openings within a certain distance of the high water mark. That means no access to crawlspaces, no doors and all your windows will be forced to be a certain height off the floor.
Another thing that you will have to do is have an engineered grading plan, this will show the existing cottage, the new addition and the elevation and slope to the entire property.
This is important in that it confirms that there will be positive drainage away from the cottage and its new addition. This helps to ensure that there will not be water damage to the new addition every time it rains.
Just because you have no openings that are below the high water mark doesn't guarantee that you will not have a flood if the water in the lake rises to the high water mark, it does how ever give you a fighting chance if there is wind blown waves that rise up and strike the cottage.
Village Builders Inc.