Gutter height

"Old_boat" wrote in news:hdtEe.37139$ snipped-for-privacy@tornado.ohiordc.rr.com:

I'm not sure what the official spec for something like this is, or even if there is one, but it seems to me that the thickness of another row of shingles is not going to cause any problems.

Does the water go into the gutter. Yes - don't worry.

It is my understanding that in areas subject to heavy snowfall, that the front edge of the gutter should be in-line with the roof plane. This allows snow that builds up on the roof to slide off onto the ground, instead of piling up on the gutter and ripping it off the building.

We get our fair share of snow in the winter, so I used this method when I installed my own gutters. It seems to work well, even in heavy rains. The only exceptions are the areas where the roof valleys channel the water into a single area. In a heavy rainstorm, these concentrated areas to tend to flow out past the gutter. I can't really raise the gutters up much, so I'm thinking it has more to do with the gutter screens blocking the flow more than the height of the gutter.

Anthony

Place a straight-edge along the roof, extending over the top of the gutter. If it touchs the gutter, and raises off the edge of the roof, then the gutter is probably high enough. If the straight-edge lays flat on the roof and passes over the top of the gutter, then water rolling off the roof is likely to do the same - shoot right over the gutter.

There are a lot of misconceptions about gutters and gutter heights within the construction community. The important rule to remember is, that with very few exceptions, water is ruled by gravity ... water falls down. This means that gutters at the edge of a roof can never be too low. In fact, they can only be too high.

The age-old rule in Architectural Graphic Standards is that the outer top edge of the gutter should be below the fall line of the roof. This is so that snow, ice, and debris will slide off of the roof over the gutter. Minimally, this prevents moisture from snow and wet debris from entering the structure and rotting the edge of the roof. Maximally, it prevents sliding ice from deforming or ripping the gutter off of the building. Lightweight roof debris is blown about by the wind, and keeping the gutter below the fall line will reduce the amount of twigs and leaves the gutter catches. And finally, if the gutter does happen to fill up with debris, moisture from the debris will contact the fascia board instead of the more absorbent roof sheathing and shingle edge.

The exact minimum dimension below the fall line is adjusted depending on the slope of the roof. The steeper the roof, the smaller the dimension needs to be (from one inch for a flat roof to as little as one-quarter inch for roofs with a 12 in 12 pitch or steeper). To determine the correct height of a gutter, lay a board flat on the sloping roof so that it extends several inches beyond the roof edge. The bottom of this board is in line with the fall line of the roof. The outer top edge of the gutter should typically be one-half inch below the bottom of the sloping board.

Like plumbing waste lines, gutter runs are minimally sloped, so that debris will flow to the downspout. The minimum slope is one-eighth inch per foot along the run. To attach the gutter at the correct sloping height, first attach the gutter location farthest away from the downspout(s) at the minimum dimension below the fall line as previously determined. This will be the high point of the gutter run. Then attach the gutter at the downspout at the low point that is determined by the minimal gutter slope for the run of the gutter (one-eight inch per foot, or ... at least one inch down for every eight feet of run). The midpoint attachments should be in line with this slope. It is important not to have any low points that could collect water and debris, so string a taught line between the previously attached high and low endpoints to accurately determine the mid-slope attachment locations.

Installing the correct roof drip edge is very important. The bottom of the drip edge should extend away from the fascia at a downward forty-five degree angle to ensure that the water drops away from the fascia and into the gutter below. Gutter shape is also important. The top of the fascia side of the gutter should be at least one-half inch above the top of the outer edge so that when the gutter overflows, water will not flow back onto the fascia.

One of the few exceptions to downward water flow can occur where there is a concentrated flow. This routinely happens at the bottom of a steep roof valley where there is a build up of water from a large roof area. The flow rate is further increased when metal valley flashing is used. At the bottom of the valley, the concentrated stream of water will overshoot the gutter. But the gutter should not be raised to solve this problem. Instead, a metal fin is routinely installed vertically from the top of the outer edge of the gutter at a valley corner. This fin extends at least one inch above the fall line of the valley (which is shallower that the fall line of the roof), and at least six inches horizontally from the outer corner of the gutter. The fin should be designed to 'break away' if it is ever hit by an ice flow.

------------------------------------- PARTI\\' :: architecture

Darn - I[ve never read so thorough a description of the how, why and where of gutters. And it is all so logical. Thanks.

" snipped-for-privacy@earthlink.net" wrote in news:au2dnR0DMoZd0yzXnZ2dnUVZ snipped-for-privacy@earthlink.com:

Yea, I archived it. All sounds good anyway.

I agree that too high is worse than too low, and that includes having any 'metal fin' that raises the edge too high. My neighbor had a fin of about 2 inches added to the entire length of one of his gutters, and around the ends. I never did exactly figure out why he did this, I assume because he thought the water was over-shooting the edge. Bottom line is when the downspout plugged up, the water backed up in the gutter, couldn't roll over the front edge so it went the other way - over the back, under the shingles and into his house!

replying to PARTIarch, t wrote: We have a shed roof and the gutter is 1/2 in below the fall line of the roof and the gutter drops down towards the downspout. For light rains, the water enters the gutter, for heavy rains, it just shoot past it. Trying to find a solution.

replying to PARTIarch, Jim wrote: Now that is a very smart, loaded with common sense, reply. Great wisdom comes with many years.

Did it take great wisdom to wait over 7 years to acknowledge PARTIarch's response?

DerbyDad03 posted for all of us...

Patience grasshopper

"To ensure that gutters drain properly, make certain they slope (½ inch for every 10 feet) toward a downspout. For gutter runs longer than 40 feet, it's best to pitch the gutter down from the middle to a downspout at each end."

I was not told this years ago when I got a second roof on top the old.

Twenty five years later, last year, I got a new roof and gutters. Shingles do seem to lap further over the gutter as I discovered cleaning them. If a new roof over this overlapped the gutters an extra inch it would be tougher to clean them.

The original question was about the height of the gutters relative to the roof, not about how far the shingles extend out. I agree with the poster that said if a piece of wood laid on top of the roof just touches to far edge of the gutter or is above it, then they are high enough. The just touching concept is for areas where snow or ice slides off, so that it will be less likely to hang up on the gutter. But the main thing is if it's working, I wouldn't worry.

The gutter needs to be behind the flashing or gutter apron, if its not then its too low and water will get behind the gutter and rot the fascia and siding.