We had a tarp to cover our run and boy was it a pain, every time it rained I worried that it was going to collapse the pen (a 10x10 dog kennel). Eventually it did and we came home to find after a heavy downpour that the top bars of the pen were bent into oblivion. We decided to suck it up and build a roof. Here's the before and after pics. After our expenses it cost us about $50....the tin was free, some of the 2x4s were free and we had to buy the 4x4 posts and 4 of the 2x4x12s for the cross pieces. The most expense was the roofing tar at $12 a gallon and we had to get 2. the tin was old and starting to rust so we have to seal it. I wish we had done this last year and we would have saved ourselves a lot of money (on replacement tarps) and heartache and worry!