The Roofing Resource Blog

3 Most Common Reasons Box Gutters Leak

Mon, Dec 23, 2013 @ 06:47 PM | Perry

box gutters indianaIf you own a home or building with box gutters then you understand the unique maintenance
challenge they can present. They are easily clogged by leaves and other debris and are often high up and hard to access, not to mention the time it takes to clean and maintain them. Also box gutters can leak in different ways when they are clogged or when they are clean which can make diagnosing the problem tricky. 

However the out of sight out of mind approach to box gutters can be even more painful than dedicating the time and effort it takes to keep gutters clean and flowing properly or complete box gutter repair. In most cases the box gutters are built into decorative wood or sheet metal trims like crown molding, cornice trim, and corbels. These trims can be very expensive to repair or replace because tin smiths are few and far between and most of the older wood molding are no longer in production and have to be custom shaped.  

Here are the three most common scenarios we have come across over the years roofing and working on box gutters. 

  • box gutter liningThey leak. Even right after a through cleaning they still leak and rain water drips through the trims. Look for pin holes or rust holes in gutter pan and/ or cracked or separated solder joints in coper or sheet metal. Leaks can occur anywhere along the box gutter but are more likely to be found in and around areas where water stands in gutter and near or in drain leading to downspout. Sheet metal  has a tendency to  corrode faster in areas where gutter holds water  than when water passes through and  gutter dries. The connection between the gutter pan and drain most often relies on a solder joint or some kind of sealant to stay watertight and is always a suspect area for leaks 

Helpful Hint : You can use a leaf blower to quickly and efficiently remove debris and water from box gutter in order to complete a thorough inspection. 


  • leaking box gutters madisonWater Spills over the front of box gutter. Water will normally spill over the front of a box gutter for one of two reasons, either the drain line is clogged and the water has to go somewhere or the amount of rain coming off the roof was too great and it overwhelmed the drain, meaning the drain couldn't carry away water fast enough and water excess rain spilled over the front of box gutter. Besides being able to see water spill over like niagara falls from you gutter when it rains, you may also identify this scenario by looking for discolored areas of trim, wood or sheet metal. The places along trim where gutter constantly overflows will have most likely have cracked, bubbled or discolored paint from dirt in water  

Helpful Hint : If you have cleaned box gutter and drain leading to downspout but water still seams to be backing up you may want to check the downspout for clogs or even underground drainage lines meant to take water away from foundation. 


  • box gutter repair madison indianaWater runs behind gutter. This is the most serious problem that can occur with box gutters because not only can trims become damaged, water often enters the home or building and damages the inside ceiling and inside of the exterior wall. This happens when the box gutters have been designed incorrectly and the front of gutter is higher or taller than the back. In an overflow situation water rises in box gutter and instead of spilling over the front of the box gutter on the sidewalk or street below the water spills over into the building.  A few signs of water entering building are water spots in the corner of ceiling and wall, water damage to interior wall, brick turning white on outside of home,  paint peeling off brick or stained, and exposed brick turning white or becoming discolor inside home. 

Helpful Hint: Create a maintenance plan, cleaning this type of gutter once in the spring and once is the fall is not even close to adequate. The gutter must be maintained very often especially when leaves are falling as they can stop up just about everyday especially if trees are near building or home.

So whats the fix?

box gutter trimThere are several options for box gutter repair that range from caulking and sealing to having box gutters lined.

Here’s what we’ve found to be the most effective, long term box gutter repair solution to all three of the most common reasons box gutters leak. We use a PVC  membrane to line box gutter in conjunction with a two pc trim detail over the decorative trim. The PVC membrane and two pc trim are commercial/ industrial roofing products that you typically find on building with flat or low slope roofs but the membrane works nicely in box gutters and is very durable.

Here’s how it works. The PVC is a water proof, fabric rein-forced membrane that is strong enough to be tear and puncture resistant, but it pliable  enough to take the shape of most all box gutters. 

Most importantly the seams are water proof and do not rely on glue but rather a hot air weld. This type of seam is an industry standard in commercial roofing and known for it durability. This same hot air weld is what unites the drain boot to the membrane and keeps water flowing inside the downspout instead of around and outside the downspout. A box gutter correctly lined with a PCV membrane will not leak, scenario 1 fixed. 

If the membrane is ran up onto the roof behind the box gutter high enough ( 6”-12” inches depending on roof pitch) and tied in properly, water will not be able to back up into home or building as we see in scenario 3.

And when the 2 pc compression detail is used over the face of box gutter as opposed to a termination bar detail, water is forced to drip off the 2 pc tim instead of running down the decorative trim on the building. The solves the problems associated with scenario 2 

Keep in mind that even though a PVC liner correctly installed and used in conjunction with a 2 pc compression detail can solve most problems with box gutters, but it wont clean your gutters for you. As will all building maintenance be smart and be safe. 

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Topics: PVC membrane, Rubber Roofing, Box Gutters