Browse Forums Outdoor Living 1 Nov 25, 2014 11:10 am Hi everyone,
I'm after some guidance and hopefully some rough pricing from people have been through this over the past few years (note: I'm in Melbourne). I'm after a basic "flat" pergola/verandah, around 12m x 2.7m – a long rectangular design. Basically, a simple metal Stratco-type design, with a mixture of colorbond sheeting and laserlite sheeting as the roof (to allow some light through). I've only had the one quote so far, for 11.5K. This wasn't Stratco, this was a local pergola specialist (name withheld) and they use bluescope steel colorbond and laserlite. As the area is already fully paved (not concreted though!), their design slopes TOWARDS the house. Their quote includes a wide box gutter that is installed alongside the house gutter, and the pipework then attaches to the existing downpipes. That way they don't need to pull up any pavers to lay any underground piping. That seems the cheap way out, and can possibly mean flooding back into the house in severe rain if the gutters overflow. They claim they've never heard of that happening though, and they do a lot of them like this. I'm curious about it all, what people are paying these days and if this sloping-back-to-the-house is common practice these days? Re: Another Verandah question - quotes + draining (slope) 2Nov 25, 2014 1:03 pm How could the box gutter overflow back into the house if the two gutters are separate? You will have an additional 32.4 sq m of roof but branching into an existing downpipe is usually not a problem because downpipes normally drain with not less than 75% air volume at their maximum flow capacity through the pop. You have also stated that it will drain to "the existing downpipes" and so you are only looking at little more than an additional 0.6 litres per second coming off the new roof to each downpipe during a 1 in 20 year storm event. I have seen numerous bad verandah installs where the new roof drains back into the existing gutter and they are non compliant nightmares during heavy rain but if the drainage is done correctly, you shouldn't have a problem. 3in1 Supadiverta. Rainwater Harvesting Best Practice using syphonic drainage. Cleaner Neater Smarter Cheaper Supa Gutter Pumper. A low cost syphonic eaves gutter overflow solution. Re: Another Verandah question - quotes + drainage (roof slop 3Nov 25, 2014 1:16 pm I may be using the wrong terminology It's a "colorbond quad guttering & flashing", which from what I gather is basically standard guttering. So what they'll do is put the house gutter side-by-side to the verandah guttering, joined together. Here's a sample... http://i.imgur.com/QjKCX2T.jpg So in the event of heavy downpours (which we do get every few years), if the gutters overflow... there's nowhere for the water to go but build up onto the verandah and back into the house. Re: Another Verandah question - quotes + drainage (roof slop 4Nov 25, 2014 3:13 pm The Melbourne 1:20 Average Recurrence Interval is slightly less than a 2.2 mm/minute average intensity over a 5 minute duration. Very hard to imagine a gutter overflowing off 32.4 sq m of roof connecting into 2 downpipes unless you have a leaf/debris blockage and even then, it would need to block the flow to both gutters. Aesthetically, the drainage in the photo looks weird, also not keen on the way it is plumbed and the retention of a rectangular downpipe if that is how they do it. I had an acquaintance (fellow car club member) and his son build me a 7.5 m x 4 m (30 sq m) carport in Feb 2011 and it is the Stratco outback. It looks great. I had it done for a good price but even so, it was way under your quote yet not much smaller. He is/was in the Melbourne outer eastern suburbs and I just gave him a call after noticing where you are; it turns out that he has retired but his son is running the business and also does your area. If you want another quote and see what he has to say, I could PM you his contact details. 3in1 Supadiverta. Rainwater Harvesting Best Practice using syphonic drainage. Cleaner Neater Smarter Cheaper Supa Gutter Pumper. A low cost syphonic eaves gutter overflow solution. Re: Another Verandah question - quotes + drainage (roof slop 5Nov 25, 2014 3:44 pm The Stratco outback design is the one I want - they're actually visiting tomorrow morning to give me a quote. The other company that quoted me already basically use a similar design to that (similar to the attached photo, minus the angled shade bit). In the photo - I have those same rectangular downpipes, I was planning on asking them to replace them with the much bigger round PVC piping if I did go with them. I'll update tomorrow once I talk to the Stratco rep. Re: Another Verandah question - quotes + drainage (roof slop 6Nov 26, 2014 2:12 pm Hi everyone, The stratco quote came in at 10.5K, so one grand cheaper. Their design is more of the standard verandah - the "outback" flat Stratco design, mounted to the house on one side, and posts on the other. It would have a few of the clear sections to get light through. It would be sloped away from the house, with guttering on the edge - but instead of digging underground for drainage, they were going to install a "reverse fall" gutter on the narrow short edge of the verandah (the 2.5m side, since it's about 2.5m x 12m), with a very slight slope back to the house and connecting to the current drainpipe. They would remove the existing thin rectangular downpipe and replace it with 100x100 tubing to allow for the additional flow, but they were only going to connect to the one downpipe. And yes please, PM me his details (or company at least), I'm actually not in Taylors Lakes anymore but not far from there either (still western suburbs). Re: Another Verandah question - quotes + drainage (roof slop 7Nov 26, 2014 4:06 pm webbiegareth The stratco quote came in at 10.5K, so one grand cheaper. It would be sloped away from the house, with guttering on the edge - but instead of digging underground for drainage, they were going to install a "reverse fall" gutter on the narrow short edge of the verandah (the 2.5m side, since it's about 2.5m x 12m), with a very slight slope back to the house and connecting to the current drainpipe. That is what I was going to suggest. The dual gutters would look ugly plus there was unnecessary additional material and labour. There was also no need to plumb to 2 downpipes and this indicated a basic lack of knowledge in flow dynamics. You will barely notice the gutter's reverse slope over 2.5 m. webbiegareth They would remove the existing thin rectangular downpipe and replace it with 100x100 tubing to allow for the additional flow, but they were only going to connect to the one downpipe. I would replace the rectangular pipe with a 90 mm round uPVC downpipe, there is no need to connect to a 100 mm. A 90 mm uPVC downpipe has an external diameter of 90 mm whereas a 100 mm uPVC downpipe has an external diameter of 110 mm (NOTE; this is not a typo), this can make it difficult to plumb the larger pipe to some gutters. A 90 mm pipe will have plenty of flow capacity because... 1. The flow capacity of a downpipe is determined by an annular vortex, having the additional entry point only makes the downpipe more efficient, it will not impact on the flow whatsoever. 2. Plumbing a 90 mm verandah downpipe to a 45 degree 90 mm F-F junction will look neat and be cheaper. 3. Even with the deficiencies of weir flow, a 90 mm round downpipe is recognised as having a flow capacity of 3.5 litres per second and some manufacturers even claim 4.2 lps. PM sent. 3in1 Supadiverta. Rainwater Harvesting Best Practice using syphonic drainage. Cleaner Neater Smarter Cheaper Supa Gutter Pumper. A low cost syphonic eaves gutter overflow solution. Re: Another Verandah question - quotes + drainage (roof slop 8Nov 27, 2014 3:34 pm Awesome, thank you - and I completely agree about the 90mm PVC pipe, as the pipe coming out underground (that attaches to the current rectangular downpipe) looks to be a 90mm PVC pipe anyway, so it'll make a nice clean connection. Re: Another Verandah question - quotes + drainage (roof slop 9Sep 03, 2015 8:36 pm The person who suggested the first option has no idea and would lead to a visual bad and hydraulically bad design. The suggested Stratco method is exactly right. I would stay well clear of the first suggestion! 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