Fascia Board Rot

Gutter Replacement

January 23, 2023

Published by Tony Waldron on January 18, 2023

BOX MITER

-Product Review-

Is it time to upgrade your gutter corner from a Strip Miter to a Box Miter? In this in depth guide for homeowners My Gutter Doctor explains everything about Box Miters from Pro’s and Con’s to F.A.Q.’s and installation tips.

GUTTER CORNERS AKA MITERS

Anytime two gutter sections meet at a corner they are connected with what is called a miter. Because of the miter water is able to make it around corners to get to the downspouts. Otherwise each individual gutter would require their own downspout to drain.

There are different types of miters such as box miter, strip miter, or bay miters. And all three of those types are available in inside-corner or outside-corner options. This may seem like a lot of information to take in but we assure you the different miters are easy to tell apart. To demonstrate the photo below shows a box miter and a strip miter side by side. To compare both styles the examples are both inside corners.

Inside Box Miter (left) beside an Inside Strip Miter (right)

WHAT IS A BOX MITER?

Inside Box Miter

Box Miters feature sleeves that the gutter sections are able to slide into. Both sections of gutter are overlapped by the miter so that the miter covers the gutters. If you were to look at an inside or outside box miter from above or below it should resemble a 90 degree angle.

Outside Box Miter (left) and Inside Box Miter (right)

STRIP MITER

Outside Strip Miter

Compared to box miters, strip miters live up to there name because they resemble a strip of metal. Strip style miters are more common on new home installations because they are cheaper and less bulky looking then box miters.

Gutter Cut At 45 Degrees For Strip Miter Installation

However they do have their con’s such as they take more time and require more precise cuts. (chances of error)

Strip Miter Overlaps The Gutter Much Less Than A Box Miter

BOX MITER PRO’S AND CON’S

When comparing Box style miters to Strip style miters, there are a few pro’s and con’s of each.

Pro’s:

Covers Gaps
Great For repairs
Easier Installation Overall

Con’s:

More Expensive
Bulky Appearance

PRO’S

-Covers Gaps-

The cuts on strip miters are precise and don’t allow for much margin of error. If the gutter is cut wrongly the strip miter will not cover the gap between the gutter and the miter. As a result the gutter will need to be replaced and cut properly to fit the strip miter. Whereas a box miter easily covers any gaps so the gutter will not need to be replaced. Having box miters on site during installations can prevent you from having to replace gutters with miters cut incorrectly.

-Great For Repairs-

In the same fashion as how a box miter will cover up any gaps from improper cuts, they will also cover gaps left from gutter damages. Strip miters that have been resealed many times over often require a box miter replacement. A lot of times the edges of the gutters become corroded from water damages. Therefore using a box miter to cover up those corroded edges is recommended.

It should be noted that box miter replacements will also require another box miter. A strip miter will not be able to be used in place of the box due to how the gutters were cut. However box miters are able to be used where strip miters used to be in place.

-Easier Installation Overall-

Box miters require less skill and experience to install then strip miters. With strip miters the gutters need to be measured and cut exactly to fit the strip miters. With strips you only have about a half inch margin of error.

Gutter Only Has About An Inch Of Overlap On Strip Miter

Whereas with Box Miters the overlap is more like 2-4 inches therefore the margin of error is greater. The goal is to have the back of the gutters line up with the back corner of the box miter. This makes it so the back corner is one large seam. Otherwise if the gutter was away from the corner there would be 3 separate seams versus the 1 seam.

Two Gutter Sections Slide Into Box Miter.

In the photo above you can see how the two gutter sections slide into the box miter. The areas where the gutters overlap the miter edges represent how much margin of error you can have when making your cuts. As long as the miter and gutter overlap they are able to be sealed and will work properly.

CON’S

-More Expensive-

Due to the much larger size that features more surface area, thus more material, Box Miters are more expensive than strip miters. In fact, Box Miters cost anywhere from two to four times as much as strip miters.

-Bulky Appearance-

Coupled with the much larger size also comes a larger appearance. Some homeowners think that Box Miters are “bulky” and prefer the Strip Miters because they are less noticeable.

The Outside Strip Miter Is Barely Noticeable On These Royal Brown Gutter Gutters

SEALING BOX MITERS

To demonstrate where a new box miter would require seals, we included the below photo of a box miter that hasn’t been sealed. In the below photo you can clearly see the two gutter sections slide into the box miter until they meet at the corner.

Box Miters Have 3 Seals That Need To Be Sealed

Although the above photo is not a new miter installation, we chose to use it because it shows the seams that need to be sealed. The two seals where the gutters overlap the miters need to be sealed from the top of the front lip to the top of the back lip. In addition the factory crimp that runs diagonal to the front tip of the miter also needs to be sealed. Polyurethane based waterproof sealants are recommended for all miter seals.

CONCLUSION

Box miters may be more expensive than strip miters but they are much easier to work with. Since you will save time using box miters over strip miters, that pretty much balances out the additional cost. Therefore it is preference of the homeowner and gutter company what type of miters are used.

For more information on Miter Installation please visit out Gutter Installation page.

For more information on re-sealing existing miters please visit our Gutter Repairs page.

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