FHB Logo Facebook LinkedIn Email Pinterest Twitter X Instagram Tiktok YouTube Plus Icon Close Icon Navigation Search Icon Navigation Search Icon Arrow Down Icon Video Guide Icon Article Guide Icon Modal Close Icon Guide Search Icon Skip to content
Subscribe
Log In
  • How-To
  • Design
  • Tools & Materials
  • Restoration
  • Videos
  • Blogs
  • Forum
  • Magazine
  • Members
  • FHB House
  • Podcast
Log In

Discussion Forum

Discussion Forum

Roof Drainage – Two Valleys…WATER!

SethFrankel | Posted in Construction Techniques on February 24, 2007 11:16am

I’m working on a remodel that creates two rather steep and larger roof valleys that drain to a single small location. Project is in Colorado so snow/damming is an issue. I’m wondering what the best design would be to collect water in such a condition. Should I create a flat area and vertical wall at the bottom with a scupper that drains? There’s a slight jog in the two roofs that would create a short (<2′) gutter, but that’s seemingly WAY undersized for the water load. This elevation faces east, FYI.

Also, once the water is off the roof, I’m looking to drain it away from the adjacent driveway and possibly lower on the side strip grass or to the street. I’m a bit concerned with freezing pipes underground. How would you design this to ensure that all this water is safely removed from the roof and then away from the house?

I’ve attached a few site photos, a roof plan and the elevation. It’s about 400k of images.

Many thanks!

Seth


Edited 2/24/2007 3:17 pm ET by SethFrankel

Reply
  • X
  • facebook
  • linkedin
  • pinterest
  • email
  • add to favorites Log in or Sign up to save your favorite articles

Replies

  1. SethFrankel | Feb 24, 2007 11:23pm | #1

    Here is the elevation/plan.

    Thanks.

    Seth



    Edited 2/24/2007 3:24 pm ET by SethFrankel

    1. Piffin | Feb 24, 2007 11:45pm | #2

      The roof section that comes to a point at the bottom of the two valleys- take that section make the pitch slightly lessfrom the peak so the bottom is 12" wide instead of a zero point. Insulate well and prevent ice damns but use I&W liberally.then if you need to control water, have a good sheet metal man build a large decorative scupper to cath and lead the water, but do not damn it up more with a wall and small scupper. That would make the problem worse and look bad.East side there means morning sun good but drifted snow bad 

       

      Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!

    2. seeyou | Feb 25, 2007 12:31am | #3

      What Piffen said, except make sure the leader box is low enough so that if it freezes, melt can't back up onto the roof, but drips off the front instead.http://logancustomcopper.com

      http://grantlogan.net/

       

      It's like the whole world's walking pretty and you can't find no room to move. - the Boss

      I married my cousin in Arkansas - I married two more when I got to Utah. - the Gourds

       

       

  2. DanH | Feb 25, 2007 01:24am | #4

    Shoot the architect.

    So convenient a thing it is to be a reasonable Creature, since it enables one to find or make a Reason for everything one has a mind to do. --Benjamin Franklin
    1. Piffin | Feb 25, 2007 02:47am | #5

      That was my first thought, but today it's my turn to be polite 

       

      Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!

      1. ANDYSZ2 | Feb 25, 2007 03:24am | #6

        Dont they make an electric element to warm the roof there to keep it from ice damming?And is it worth doing?

        ANDYSZ2WHY DO I HAVE TO EXPLAIN TO FRIENDS AND FAMILY THAT BEING A SOLE PROPRIETOR IS A REAL JOB?

        REMODELER/PUNCHOUT SPECIALIST

         

        1. seeyou | Feb 25, 2007 03:42am | #7

          >>>>>Dont they make an electric element to warm the roof there to keep it from ice damming?And is it worth doing?That's basically the same thing as putting a tent over the house so the roof doesn't leak. Design and execution will solve the problem 99% of the time without having to resort to things like heat cables.http://logancustomcopper.com

          http://grantlogan.net/

           

          It's like the whole world's walking pretty and you can't find no room to move. - the Boss

          I married my cousin in Arkansas - I married two more when I got to Utah. - the Gourds

           

           

          1. SethFrankel | Feb 25, 2007 04:04am | #8

            Well, I'd rather not commit to a heat cable. While damming is a concern, I think that we can certainly design the insulation to prevent that. I'm really more concerned with such a large surface of roof and possible snow to melt and overwhelm the gutter/downspout. I do appreciate the idea of a flat spot, but guys, where's your sense of historic roof pitch! I'd say that the design is rather committed to this angle...the front portion of the house is driving the angle so the new back is just following suite.Maybe a separation of the two roofs with keeping the same pitch? I do have very severe limitations as to foot print in this project so pulling them apart will be really challenging.Thanks.
            Seth

          2. seeyou | Feb 25, 2007 04:41am | #9

            >>>>>>>where's your sense of historic roof pitch!It's right beside our sense of historic roof problems.http://logancustomcopper.com

            http://grantlogan.net/

             

            It's like the whole world's walking pretty and you can't find no room to move. - the Boss

            I married my cousin in Arkansas - I married two more when I got to Utah. - the Gourds

             

             

          3. SethFrankel | Feb 25, 2007 05:13am | #11

            Ouch.

          4. Piffin | Feb 25, 2007 03:02pm | #15

            Your drawing dioes not allow the same historic poitch as show now so why worry whether you are changeing from 12/12 to 7/12 or to 6/12? 

             

            Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!

        2. Piffin | Feb 25, 2007 03:00pm | #14

          Those are afterthoughts to cover for bad design and willhelp with the ice problem but not the bottle neck of excessive water flow 

           

          Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!

    2. User avater
      PeteDraganic | Feb 25, 2007 07:13pm | #29

      ROFLMAO!!

      My thoughts exactly!

       

      When you're this good, EVERYONE wants a crack at you!

      http://www.petedraganic.com/

  3. theslateman | Feb 25, 2007 04:45am | #10

    This design and your needs to accomodate the water flow and the protection from ice backup are at odds with one another.

    It would be possible in a warmer climate to control the water flow thru a method like you suggest. When you have potential for backup issues then it would be more beneficial to not try and constrain the flow.

    To capture the amount of fast flowing water in warm weather you would need a substantial barrier at the base of those valleys or the water will shoot right over your gutters. If you were to do that to control warm weather run off, it will impede the cold weather precipitation from being able to slide off or flow increasing the likelihood that you'll have backup- no matter what insulation and venting you undertake.

    If your design is cast in stone and you must control the water flow- then be prepared to use metal in that area up both valleys for at least 8' including the center section- leading up to a large scupper and front wall.

    This is not an easy solution to do all that you need in that climate.

    Walter

    1. SethFrankel | Feb 25, 2007 05:18am | #12

      Thanks, Walter.Reading the various suggestions, perhaps I should consider lowering the south peak (lefthand in the drawing). I can lower it probably a foot or so and thereby widen the area that joins the existing roof. I appreciate the conflict you point out about fast flowing water spilling over and cold water damming and freezing. It sound like we'll need to consider carefully the materials in that area, do as much metal as possible, and dramatically oversize the gutter/downspout configuration to deal with this.I appreciate the advise.Seth

      1. User avater
        Jeff_Clarke | Feb 25, 2007 09:21am | #13

        Shoot ..... who??? ;o)

         

        Jeff

        Edited 2/25/2007 1:21 am ET by Jeff_Clarke

        1. SethFrankel | Feb 25, 2007 04:40pm | #16

          Good looking! Thanks for posting.Seth

          1. Piffin | Feb 25, 2007 05:26pm | #20

            That scupper head is the kind of collector I was referring to.If you cahnge roof pitch to have a 12" eave on that section, the collector can be shaped similar to the triable that is left at the vertex of the adjacent roofs so the pitch change never shows. all - could somebody reply to me? I have a hanging reply because I got one that was deleted and this thread will be popping up in my folder forever unless I can relink that cookie. 

             

            Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!

          2. Stilletto | Feb 25, 2007 05:27pm | #21

            reply 

             

          3. Piffin | Feb 25, 2007 05:29pm | #22

            Thanks!
            Anybody ever tell you how fast you are? 

             

            Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!

          4. Stilletto | Feb 25, 2007 05:31pm | #23

            Just returning the favor,  you helped me yesterday with tiny text.  

             

          5. theslateman | Feb 25, 2007 06:07pm | #26

            Seth,

            The picture Jeff has posted is for a decorative item- conductor head.

            The water from a gutter is conducted into this then the downspout is fastened at the bottom. This item isn't weant to act as a scupper at roof level, but secured under the soffits as a decorative feature.

            You could have fabricated something more rugged which might be incorporated though.

            Walter

          6. User avater
            Jeff_Clarke | Feb 25, 2007 07:05pm | #28

            Decorative ... but also very functional.  Available in 20 oz copper - in my book that's pretty damn rugged (just bought one in 20 oz.).  I see nothing wrong with a conductor head taking water from a valley as opposed to gutters - right?   He could also have a 20 oz. copper collection box fabricated to pick up drainage at the roof level.

            See attachment for one we just had made up - for a 90 degree intersection.  Pardon the markups!

             

            Jeff

          7. theslateman | Feb 25, 2007 08:41pm | #31

            Jeff,

            Yes 20 oz. is fairly rugged- plenty strong if that were used under the soffits and possibly strong enough if used at roof level too.

            I wasn't finding fault with it - just pointing out it was meant for another application.

            Certainly Seth could have something fabricated for this specific location that could collect rainwater and discharge it.  The problem arises when it's no longer liquid.

            See attached pictures.  I was shooting into the sun so they didn't come out great.

            Walter

          8. theslateman | Feb 25, 2007 08:49pm | #32

            Seth,

            I just posted some pictures of a roof with valleys meeting at a narrow point. Previous post to Jeff Clarke. This area faces North so it gets no sun all Winter.

            Many Winters I've had to manually remove the huge ice and snow deposits from  both sides of this large dormer.  It can't free itself once ice starts forming.We haven't had huge storms this Winter so this area hasn't leaked yet. One more good snow storm and it well might. 

            In your case if it were to rain once you had socked in snow and ice it could be a big problem.  There are a number of possible methods to adopt if the design must remain as is.

            Walter

          9. SethFrankel | Feb 25, 2007 09:40pm | #34

            Walter,Goodness! That's a photo I'd rather not be able to take at this house!The good thing in Colorado is that it's rarely cold for more than a few days in a row and the sun is rather strong even in worst of winters. The issues here will be the fast snow and then a quick melt that would overwhelm. Ice damming can (and will) occur, but it's not as quite dramatic as I think you'll find in your neck of the woods.Thanks.Seth

      2. theslateman | Feb 25, 2007 04:47pm | #17

        Seth

        There  is one more radical thing that I've thought of in regards to ice forming then back up occuring. I'm going to take a picture later today of a situation similar to yours- except it faces North.

        It may be in that small area at the bottom of those valleys which will lock in snow and ice even without an elevated scupper- you might consider a loop of radiant heat underneath the roofs sheathing just in that area. This would keep the accumulations able to flow out of this bottleneck and not able to form an ice dam.

        They use radiant for sidewalk heating so why not in this somewhat unusual situation.

        Picture will be posted later after I return from Bangor.

        Walter

        1. SethFrankel | Feb 25, 2007 05:01pm | #18

          Walter,I'll look for the photo later. FYI, there will be radiant in-floor heat at that location on the second floor. Of course, I'd worry about freezing of the radiant tubing, if the whole system was not also injected with glycol.Thanks for taking the time to help problem solve.Seth

          1. peteshlagor | Feb 25, 2007 05:35pm | #24

            I do like those pavers, however!

            Nice pattern.  How's it do when plowing, shoveling, or blowing?

             

             

          2. SethFrankel | Feb 25, 2007 06:29pm | #27

            Thanks.The pavers are just fine in the winter. Sure, there's a little snow that's always between the tracks, but it's really not a big deal. I've used a snowblower just fine as well.In my situation, the trick is the water that dumps from the existing gutters and refreezes. I'm thinking about creating an open channel down the center with a metal grill and run all the water from this problem roof area down that channel into the street (i.e. skating pond in the road...).It's been in place for about six years, so there are definately tire tracks that are about 1/2" lower than the center/edges, but it doesn' effect the use. Of course, I'm expecting to need to take up the pavers and level the sand again after this construction project...Seth

          3. User avater
            PeteDraganic | Feb 25, 2007 07:25pm | #30

            Seth,

            The scupper idea is about the only "normal" solution to this, however, it may look grossly out of place on the front of this home.  IT would have to be large enough to capture the large amount of water being funneled to the point... and would have to drain fast enough, meaning a large-diameter drain pipe... then you have the dynamic of swirling causing a loss of efficiency in draining.

            Not to mention the severe problem of ice damming for a considerable distance up the roof.

            If you leave as is, you will DEFINITELY want to add a heater cable.... not to the roof but inside the scupper and drain pipe to keep it from damming.

            Here is another idea.... don't know if it would conform to your situation but I would consider cutting a trough drain into the roof in that valley... like maybe 4' from the bottom... maybe even 6' up.  this can be flashed and drained from below (inside the attic) and then exited elsewhere.

            OR

            you could build a built-in gutter at the same height, on the surface of the roof and drain that along the exterior.  I'm talking about the type they used to be an integral part of the roof.  I don't recall the name at the moment.  This would divert the water before it came to the point of concentration where it becomes problematic.

             

            When you're this good, EVERYONE wants a crack at you!

            http://www.petedraganic.com/

            Edited 2/25/2007 11:28 am ET by PeteDraganic

          4. SethFrankel | Feb 25, 2007 09:32pm | #33

            Thanks, Pete. Both interesting ideas and worth toying around with. I think this might be a situation to implement a few of these ideas rather than hoping a single solution will work.Seth

          5. User avater
            Jeff_Clarke | Feb 25, 2007 09:49pm | #35

            See attached.

            Ice dams are caused by heat escaping through the roof.   Heating with cables ABOVE the roof is a totally different concept - and much new construction in Colorado does it - it's not a design flaw there to need it.

            http://www.chromalox.com/products/prodinfo/en/srfrg.html

             

            Jeff

            Edited 2/25/2007 10:01 pm ET by Jeff_Clarke

          6. SethFrankel | Feb 25, 2007 09:58pm | #36

            Jeff,You rock.Thanks for taking the time to provide such detail.Seth

          7. User avater
            Jeff_Clarke | Feb 25, 2007 10:17pm | #37

            My pleasure!

            Jeff

        2. ANDYSZ2 | Feb 25, 2007 05:12pm | #19

          That's what I was suggesting with an electric heating element he could still put on the scupper and run heat in the scupper and under the roof to keep the icedam from forming at the bottle neck but others thought that too gimicky.

          ANDYSZ2WHY DO I HAVE TO EXPLAIN TO FRIENDS AND FAMILY THAT BEING A SOLE PROPRIETOR IS A REAL JOB?

          REMODELER/PUNCHOUT SPECIALIST

           

          1. theslateman | Feb 25, 2007 05:58pm | #25

            Andy,

            I think people thought you were suggesting a heat cable externally- I'm thinking that a loop inside the structure might have merit.

            Walter

Log in or create an account to post a comment.

Sign up Log in

Become a member and get full access to FineHomebuilding.com

Video Shorts

Categories

  • Business
  • Code Questions
  • Construction Techniques
  • Energy, Heating & Insulation
  • General Discussion
  • Help/Work Wanted
  • Photo Gallery
  • Reader Classified
  • Tools for Home Building

Discussion Forum

Recent Posts and Replies

  • |
  • |
  • |
  • |
  • |
  • |
View More Create Post

Up Next

Video Shorts

Featured Story

FHB Podcast Segment: Can You Have Too Many Minisplits?

There are some instances where multiple minisplits make sense.

Featured Video

A Modern California Home Wrapped in Rockwool Insulation for Energy Efficiency and Fire Resistance

The designer and builder of the 2018 Fine Homebuilding House detail why they chose mineral-wool batts and high-density boards for all of their insulation needs.

Related Stories

  • Repairing a Modern Window Sash
  • Landscape Lighting Essentials
  • Podcast Episode 694: Bath Fans, Too Many Minisplits, and Second-Story Additions
  • FHB Podcast Segment: Can You Have Too Many Minisplits?

Highlights

Fine Homebuilding All Access
Fine Homebuilding Podcast
Tool Tech
Plus, get an extra 20% off with code GIFT20

"I have learned so much thanks to the searchable articles on the FHB website. I can confidently say that I expect to be a life-long subscriber." - M.K.

Get home building tips, offers, and expert advice in your inbox

Signing you up...

This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.
See all newsletters
See all newsletters

Fine Homebuilding Magazine

  • Issue 332 - July 2025
    • Custom Built-ins With Job-Site Tools
    • Fight House Fires Through Design
    • Making the Move to Multifamily
  • Issue 331 - June 2025
    • A More Resilient Roof
    • Tool Test: You Need a Drywall Sander
    • Ducted vs. Ductless Heat Pumps
  • Issue 330 - April/May 2025
    • Deck Details for Durability
    • FAQs on HPWHs
    • 10 Tips for a Long-Lasting Paint Job
  • Issue 329 - Feb/Mar 2025
    • Smart Foundation for a Small Addition
    • A Kominka Comes West
    • Making Small Kitchens Work
  • Issue 328 - Dec/Jan 2025
    • How a Pro Replaces Columns
    • Passive House 3.0
    • Tool Test: Compact Line Lasers

Fine Home Building

Newsletter Sign-up

  • Fine Homebuilding

    Home building tips, offers, and expert advice in your inbox.

  • Green Building Advisor

    Building science and energy efficiency advice, plus special offers, in your inbox.

  • Old House Journal

    Repair, renovation, and restoration tips, plus special offers, in your inbox.

Signing you up...

This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.
See all newsletters

Follow

  • Fine Homebuilding

    Dig into cutting-edge approaches and decades of proven solutions with total access to our experts and tradespeople.

    Start Free Trial Now
    • Facebook
    • Instagram
    • X
    • LinkedIn
  • GBA Prime

    Get instant access to the latest developments in green building, research, and reports from the field.

    Start Free Trial Now
    • Facebook
    • YouTube
  • Old House Journal

    Learn how to restore, repair, update, and decorate your home.

    Subscribe Now
    • Facebook
    • Instagram
    • X
  • Fine Homebuilding

    Dig into cutting-edge approaches and decades of proven solutions with total access to our experts and tradespeople.

    Start Free Trial Now
    • Facebook
    • Instagram
    • X
    • LinkedIn
  • GBA Prime

    Get instant access to the latest developments in green building, research, and reports from the field.

    Start Free Trial Now
    • Facebook
    • YouTube
  • Old House Journal

    Learn how to restore, repair, update, and decorate your home.

    Subscribe Now
    • Facebook
    • Instagram
    • X

Membership & Magazine

  • Online Archive
  • Start Free Trial
  • Magazine Subscription
  • Magazine Renewal
  • Gift a Subscription
  • Customer Support
  • Privacy Preferences
  • About
  • Contact
  • Advertise
  • Careers
  • Terms of Use
  • Site Map
  • Do not sell or share my information
  • Privacy Policy
  • Accessibility
  • California Privacy Rights

© 2025 Active Interest Media. All rights reserved.

Fine Homebuilding receives a commission for items purchased through links on this site, including Amazon Associates and other affiliate advertising programs.

  • Home Group
  • Antique Trader
  • Arts & Crafts Homes
  • Bank Note Reporter
  • Cabin Life
  • Cuisine at Home
  • Fine Gardening
  • Fine Woodworking
  • Green Building Advisor
  • Garden Gate
  • Horticulture
  • Keep Craft Alive
  • Log Home Living
  • Military Trader/Vehicles
  • Numismatic News
  • Numismaster
  • Old Cars Weekly
  • Old House Journal
  • Period Homes
  • Popular Woodworking
  • Script
  • ShopNotes
  • Sports Collectors Digest
  • Threads
  • Timber Home Living
  • Traditional Building
  • Woodsmith
  • World Coin News
  • Writer's Digest
Active Interest Media logo
X
X
This is a dialog window which overlays the main content of the page. The modal window is a 'site map' of the most critical areas of the site. Pressing the Escape (ESC) button will close the modal and bring you back to where you were on the page.

Main Menu

  • How-To
  • Design
  • Tools & Materials
  • Video
  • Blogs
  • Forum
  • Project Guides
  • Reader Projects
  • Magazine
  • Members
  • FHB House

Podcasts

  • FHB Podcast
  • ProTalk

Webinars

  • Upcoming and On-Demand

Podcasts

  • FHB Podcast
  • ProTalk

Webinars

  • Upcoming and On-Demand

Popular Topics

  • Kitchens
  • Business
  • Bedrooms
  • Roofs
  • Architecture and Design
  • Green Building
  • Decks
  • Framing
  • Safety
  • Remodeling
  • Bathrooms
  • Windows
  • Tilework
  • Ceilings
  • HVAC

Magazine

  • Current Issue
  • Past Issues
  • Magazine Index
  • Subscribe
  • Online Archive
  • Author Guidelines

All Access

  • Member Home
  • Start Free Trial
  • Gift Membership

Online Learning

  • Courses
  • Project Guides
  • Reader Projects
  • Podcast

More

  • FHB Ambassadors
  • FHB House
  • Customer Support

Account

  • Log In
  • Join

Newsletter

Get home building tips, offers, and expert advice in your inbox

Signing you up...

This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.
See all newsletters
See all newsletters

Follow

  • X
  • YouTube
  • instagram
  • facebook
  • pinterest
  • Tiktok

Join All Access

Become a member and get instant access to thousands of videos, how-tos, tool reviews, and design features.

Start Your Free Trial

Subscribe

FHB Magazine

Start your subscription today and save up to 70%

Subscribe

Enjoy unlimited access to Fine Homebuilding. Join Now

Already a member? Log in

We hope you’ve enjoyed your free articles. To keep reading, become a member today.

Get complete site access to expert advice, how-to videos, Code Check, and more, plus the print magazine.

Start your FREE trial

Already a member? Log in

Privacy Policy Update

We use cookies, pixels, script and other tracking technologies to analyze and improve our service, to improve and personalize content, and for advertising to you. We also share information about your use of our site with third-party social media, advertising and analytics partners. You can view our Privacy Policy here and our Terms of Use here.

Cookies

Analytics

These cookies help us track site metrics to improve our sites and provide a better user experience.

Advertising/Social Media

These cookies are used to serve advertisements aligned with your interests.

Essential

These cookies are required to provide basic functions like page navigation and access to secure areas of the website.

Delete My Data

Delete all cookies and associated data