Also box gutters can leak in different ways when they are clogged or when they are clean which can make diagnosing the problem tricky. roofing and working on box gutters. They leak. Even right after a thorough cleaning they still leak and rain water drips through the trims.Click to see full answer. In this manner, how much does it cost to replace box gutters?Box gutter repair costs an average of $20 to $50 per linear foot. Those with a curved structure cost an average of $40 to $50 per linear foot for materials only, and installation costs can run an extra $70 to $100 per linear foot.Additionally, what fall should a box gutter have? (i) Fall or slope Box gutters to be installed with a minimum uniform fall of 1 in 200 towards the outlet. This effectively states that all box gutters must allow for 30mm of “freeboard” which is from the overflow point eg. Keeping this in view, why do box gutters leak? When a box gutter becomes clogged by leaves, dirt and/or debris, it simply can’t drain water properly. This causes the water to spill over the front of the gutter.Should I repair or replace gutters? You probably need to replace your gutter if… There are lots of little repairs that must be made. If your gutters are riddled with cracks, holes, or rust spots throughout, then your best best is to replace the entire guttering system.