Hire the best Roofing Expert

Converting box gutters and extending eaves

Results 1 to 10 of 10
  1. #1
    Novice
    Join Date
    Aug 2020
    Location
    ACT
    Posts
    36

    Default Converting box gutters and extending eaves

    I'm looking at converting the concealed/box guttering on my gable ended house (so 2 straight lengths). I wasn't wanting to embark on doing this as it's a lot of work, but with the soffits out I got to witness the (recently cleaned!) guttering fail spectacularly in a heavy downpour and see how much water would have been streaming into the eaves. This has clearly been going on a long time as the wood has rotted in the eaves and mud had built up.

    Due to the shape of the roof and some brickwork, in order to convert to an external gutter system, I will need to extend the roofline by 1 row of tiles on each side. What to do is fairly straightforward but thought I would check to see if there are any framing code/standards issues. The roof is a truss system and the top chord or "rafter" extends 800mm past the timber wall frame (not the outside of the brick veneer), the rafter needing to be extended by around 300mm . I was thinking of attaching similar dimension lumber to the side of the existing truss around 1.5m or longer. This way, the rafter is extended, and there's also some extra strength over the wall frame area to counteract any additional cantilevering effect from the extra row of tiles.

    This would also make the edge of the roofline slightly below the tops of the windows, not a big deal to me but I thought I'd check. I'm yet to finalise how the soffits will fit, maybe all angled, maybe part angled part level etc.

  2. #2
    Golden Member
    Join Date
    Oct 2017
    Location
    Melbourne - Yarra Ranges
    Posts
    593

    Default

    Zero experience on this. Maybe a picture or 2 would assist with responses?

  3. #3
    Novice
    Join Date
    Aug 2020
    Location
    ACT
    Posts
    36

    Default

    Yeah here is a rough before and after. Dimensions aren't to scale but you get the idea of where I'm attaching new wood.
    before.jpgafter.jpg

  4. #4
    Golden Member
    Join Date
    Oct 2017
    Location
    Melbourne - Yarra Ranges
    Posts
    593

    Default

    Ok, as I said, havn't seen or done this before and assume by your diagram a full or part tile is all thats needed to extend the existing roof line.
    Other options without the need to extend the rafters perhaps:
    1. use a full tile and tuck more of the tile under the last
    2. cut the tiles to a length that fits without the need to extend the rafters?

    If so, it would mean the new fascia would simply replace the old fascia as per a normal exposed gutter setup and the cut end of the tile tuck up under the existing tile.
    or can

  5. #5
    2K Club Member
    Join Date
    Dec 2009
    Location
    Melbourne
    Posts
    2,555

    Default

    Have you considered improving the efficiency of your gutter by adding another downpipe or replacing with a larger diameter downpipe - e.g. round instead of square.

    Could the box gutter be replaced with a deeper/wider one to inceprease capacity?

  6. #6
    Novice
    Join Date
    Aug 2020
    Location
    ACT
    Posts
    36

    Default

    I did look at how to work with the existing box gutters, but I just came to a conclusion that they are a giant liability in terms of leaking into the wall cavity. Not to mention it would probably be just as much work to deal with what's already there.

    So I thought I had all my design in order, but have one snag. On most houses with a gable end roof, the tiles go all the way to the edge and therefore the water can drip off onto the ground. This house has a fascia board at the edge, then a "secret gutter" (I think it's called) channel that runs parallel down the roofline, but sits around 70mm lower than the tops of the roof tiles. This channel then is cut into the box gutter, which means that the wall of the gutter at that point is only a few 10's of mm high. This is one of the major leakage points.
    I forgot to consider that because it sits lower than the top of the tiles, continuing that channel in the new design would result it in coming out halfway down the front fascia board

    OK, so one idea is to actually cover the entire channel by installing a 140mm wide L shaped flashing piece, so that a continuous piece of flashing covers the edge of the side fascia boards, then comes in 140mm covering the channel and directing water well onto the roof tiles. I'm not sure how that would seal over the existing concrete pointing tiles at the top though. I have seen roofs where there's metal capping going over the concrete pointings, though I'm not sure what I'm looking for. Most of the flashing seems to based around modern colorbond roofs. Any ideas?

  7. #7
    Newbie
    Join Date
    Jul 2021
    Location
    ACT
    Posts
    1

    Default

    How did you go with your box gutter conversion?
    I've just stumbled upon your thread. I have exactly the same issue and also want to convert to standard gutters.

  8. #8
    Apprentice (new member)
    Join Date
    Jul 2021
    Location
    Rosanna
    Posts
    1

    Default

    Quote Originally Posted by Amerli View Post
    How did you go with your box gutter conversion?
    I've just stumbled upon your thread. I have exactly the same issue and also want to convert to standard gutters.
    Hey Amerli, we have just started our box (concealed) gutter to external gutter conversion, so thought I would share the details. In our case we're not extending the eaves; rather the rafter tails will be trimmed to hang the external gutters. I have attached section sketches of old vs new gutters, at least as I understand it...!

    We've only just started. So far we have had the eaves soffit linings removed by professional asbestos removers. (House was built in 1970's so most likely AC sheet.) Next stage is new gutters, which will be done by the roof plumber who will need to remove old timber fascias and 'plumb cut' the rafter tails before installing new colorbond fascias and standard quad gutters.

    old-gutters.jpg new-gutters.jpg img_7725.jpg

  9. #9
    Novice
    Join Date
    Aug 2020
    Location
    ACT
    Posts
    36

    Default

    Quote Originally Posted by Amerli View Post
    How did you go with your box gutter conversion?
    I've just stumbled upon your thread. I have exactly the same issue and also want to convert to standard gutters.
    Don't know how I missed this thread, I usually see the updates. Anyhow, I have gone through most of the conversion. I extended the truss ends, repositioned and added batten rows, new row of tiles, then new fascia board and gutters. Next I have to frame up the eaves to hold new soffits, but I'm holding off till after I put new windows in so I can frame up the soffits accurately with the windows.

    Definitely a big job with lots of little traps that I would have approached differently if I knew from the beginning. I would probably gently slope the angles of the truss extension so that when you're finished, the roof line has a 1:500 or 1:1000 slope in a particular direction. This is so that it's easier to position the gutters on the fascia, so that you can make the gutters fairly level with the fascia, but maintain a good slope for water flow, getting more like a 1:300 slope. One of my gutters had to go against the slope of the fascia so It's quite askew compared to the fascia.

    Also, my soffits aren't going to be level, since the fascia slot now sits a little lower than previously. I don't know whether this is a big deal. I don't think it will be visually noticeable, and luckily it is sloping away from the house, so in the event that water gets into the eaves, it should drain outwards away from the house, rather than leaking into the walls.

  10. #10
    Je pense, donc METRIX's Avatar
    Join Date
    Apr 2012
    Location
    Sydney North
    Posts
    9,240

    Default

    I have done this on a previous house, it was traditional rafter construction with 1m eaves.
    It was fairly straight forward, remove all the concealed guttering, string line across all the rafters, mark and plumb cut them, double up any rafters that were beyond repair.

    New fascia and guttering, it all went pretty smoothly.
    Mieux vaut prévenir que guérir

Similar Threads

  1. Replies: 28
    Last Post: 27th Mar 2012, 10:49 PM
  2. Adding eaves to a skillion roof with no eaves
    By turbora28 in forum Roofing
    Replies: 15
    Last Post: 8th Oct 2010, 06:27 PM
  3. Converting hidden gutters
    By gray71 in forum Roofing
    Replies: 0
    Last Post: 6th Oct 2009, 03:04 PM
  4. converting built in gutters anyone want to do it?
    By Gravy258 in forum Structural Renovation
    Replies: 0
    Last Post: 4th Nov 2007, 12:53 PM
  5. Replies: 2
    Last Post: 15th Jul 2005, 01:03 PM

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •