Heres a link to a pic of the covered bridge in St. Martins, NB.
https://www.flickr.com/photos/jarviseye/4700374715
In the centre it's 4 metres - just over 13 feet. On the sides it slopes to 3.1M (10 ft). That's probably typical of most coveed bridges in he prvince. There may be a safety measure of a foot or so built in to those restrictions (ie the heights may be slightly more than stated), I'm not sure. St. Martins is a beautiful community about 30 miles from Saint John. There are 2 campgrounds, almost beside one another, in the town that I'm aware of.