A very common problem is zippers not zipping properly or failing.

9 times out of 10  a  zipper problem is caused by rafters being too long which prevents the door from zipping easily.

If you have a tight zipper you must take a minimum of 1" off of the rafters nearest the door. If your entire roof is tight take 1" off each rafter.  If after reducing rafters by 1 inch, and the entire roof is still tight, you must take off another 1" off each rafter. 

Having too long of rafters will eventually destroy your door zippers and weaken the seams due to constant pressure on them.

There is no warranty on zippers if you have too long of rafters causing the zippers to fail.

We will gladly take care of the issue if the zipper problem is not caused by rafters cut too long.