Browse Forums Eco Living 1 Nov 06, 2012 10:26 pm I'm trying to decipher, from the myriad of Lysaght gutter choices, what would best be suitable to fit to the new kit home. The kit home company have advised they supply 'QUAD 115 Hi-front slotted' as standard. The house roof area is 235 sqmts with a 20 degree pitch gable and 5 degree pitch awnings. There will be two 16 meter long gutters. Each gutter will have 2x 100mm downpipes. These will be located 4mts in from the ends of each awning, so as to effectively service equal amounts of roof area. Do I go slotted, unslotted, high front, quad? How do I determine what size will do the job? Is there a guideline or formula to follow? jnk40 Re: Which gutter? 2Nov 08, 2012 1:47 am Hi John, Once again, great sketch. Let's go through this step by step. Compliance for the roof area harvested to each downpipe is determined by the gutter and downpipe size and the area's rainfall intensity. The downpipe is fitted to the gutter's low point and the high point between the downpipes determines the available slope and the roof area harvested by each downpipe. Eaves gutter compliance is designed to cope with a 1 in 20 year average recurrence interval (1:20 ARI) without overflowing. Box gutters are required to cope with a 1:100 ARI. The ARI is based on a 5 minute intensity. From your water tank thread, I know your location is Gympie, QLD. You are fitting eaves gutters and Gympie and nearby areas have a 1:20 ARI of either 220 or 230 mm per hour or an average of 3.8 mm per minute for a five minute duration. If you click the Lysaght link on your first post, click again on LYSAGHT QUAD gutter at the top where it also shows a photo of the gutter. Scroll down to BROCHURES and click LYSAGHT® Rainwater Solutions Queensland. Page 5, table 2 shows different gutters, the gutter's cross sectional area and their downpipe size. You will notice that some gutters are slotted and you will also notice that the cross sectional area of the gutters that have optional slots is smaller than the standard unslotted gutters cross sectional area. This means that a slotted gutter has a lesser carrying capacity than the same profile unslotted gutter. The two gutter at the top of table 2 are the QUAD 115, slotted and unslotted. You are being supplied this gutter as a slotted option for your home. It has a cross sectional area of 5,285 sq mm and the designated downpipes are either 75 x 75 mm or 90 mm round. EDIT: Note that the building company has stated that 100 mm downpipes would be fitted to this gutter but the gutter cannot accept this size. The house roof area is 235 sq metres, equally divided into two halves of 117.5 sq m each. To calculate the roof area for compliance, the two different roof slope(s) are factored to allow for wind driven rain during a storm. A 20 degree pitch roof area is subject to a multiplier of 1.18 and if the sloped area was let's say 70 sq metres, then that roof section would be factored as 70 x 1.18 = 82.6 sq m. As we don't know the exact areas of the different sloped rooves, let's guesstimate a factored roof area of 130 sq m each side. Figure 1 is to the left of table 2. This table is missing some detail, possibly because of Australian Standards copyright issues. Nevertheless, the QUAD 115 slotted gutter to be supplied for your home shows a cross sectional area of 5,285 sq mm. Look for the graph's approximate value on the bottom line. You next find Gympie's 1:20 ARI (230 mm hr). The table jumps from 200 to 300 mm/hr in the sample but you should find where the cross section area and the 230 mm/hr line is likely to be. You then look to the left and that will tell you the maximum factored roof area that each downpipe can drain on your house. For your house and for compliance, each downpipe can only drain a maximum factored roof area of 22 sq metres which means that SIX 90 mm downpipes are required on each side for compliance!!! Huston, we have a problem! The QUAD 115 slotted is clearly too small! First thing to do is refuse the slotted gutters. The QUAD 115 is too low on the back wall, only 62 mm as shown on your first post AND OF COURSE THE SLOTS ARE EVEN LOWER!!! For Queensland, neither version should be considered. AS/NZS3500.3 (2003) states: "Eaves gutter systems, including downpipes, shall be designed and installed in accordance with clause 3.2 so that water will not flow back into the building". Overflowing gutters are a scourge and the popularity of high fronted gutters combined with non compliant installations cause hundreds of millions of dollars damage every year when the gutters back flow into the building. High fronted gutters are popular because they hide the fascia, a case of aesthetics subjugating function. If we go to the page under the tables, we see that the next gutter listed in table 2, the QUAD Hi Front 150, also has the same low back of 62 mm but a much wider width. The table however shows that the slotted version has a greater cross sectional area than the standard gutter. Clearly this is wrong as they are the same gutter but the standard gutter's height for determining the cross sectional area is taken as 10 mm below the lowest wall whereas the slotted gutter is measured 10mm below the bottom of the slots. The document is shown as last updated on June 26, 2012 but it is a mistake...and a bad one. The QUAD Lo Front 150 (actually 140 mm wide) has a back wall 78 mm high, a front wall 74 mm high, takes a 100 mm round downpipe and should the gutter overflow, it will be over the front. The cross sectional area is 8,631 sq mm and if you go to figure 1 again and intersect the new cross section area with the 230 mm/hr ARI, you will find it is compliant for a roof area in Gympie of about 40 sq m. If you fit the QUAD Hi Front 115 guttering that the company intends supplying, you will have massive overflows unless many downpipes are fitted. As you will also be dependent on harvested water, the issue goes beyond mere nuisance value. EDIT: Compliance and good design are worlds apart. Just because roof drainage is compliant does not mean that it will cope with a 1:20 ARI if it is an eaves gutter or a 1:100 ARI if it is a box gutter. The majority of new homes have poorly designed roof drainage and the three primary (is that an oxymoron?) reasons are... (1) Aesthetics subjugating function. (2) Lack of regulatory understanding due to confusing and expensive manuals. (3) Poorly written regulations. Examples of (1). Downpipes plumbed at the end of walls and away from the greater roof area. Downpipes plumbed long distances apart. Examples of (2). You need to be a mathematician to understand many examples and most plumbers simply do not qualify. The industry is unnecessarily multi layered and there are many manuals and booklets. Not all are regulatory while some others are referred to as "Deemed To Satisfy", meaning that their regulations can be "called up" to replace the primary regulation. In many instances, the regulation used is inferior. Examples of (3). A lower gutter receiving a concentrated discharge from a downpipe draining an upper roof is not regulated to have a downpipe plumbed to the area that receives that discharge. In many instances, the downpipe will be at the other end of the gutter due to (1). Regulations do not require downpipes to be plumbed close to the largest roof areas. And off another thread... The whole situation of the BCA versus Australian Standard is a mess! Look at the below and the chain of command 1. COAG is in charge (politians only & govt depts) Council of Australian Government! 2. ABCB (Australian Building Codes Board) runs or is the writing body for COAG - and is in charge of the NCC! 3. NCC is the National Construction Code which comprises the BCA & PCA! 4. BCA is the Building Code Australia. 5. PCA is the Plumbing Code of Australia! 6. The ABCB only came into existance in 1994 but was only validated this year in April 2012???? 7. The ABCB comprises of two advisory committes - the BCC and the PCC! 8. The BCC is the Building Codes Committee 9. The PCC is the Plumbling Codes Committee The BCC consists of: ABCB Office (Chair) A representative of the Australian Government A representative of each of the State and Territory Governments A representative of Local Government Australasian Fire Authorities Council Australian Institute of Architects Australian Institute of Building Australian Institute of Building Surveyors Building Designers Association Building Products Innovation Council Commonwealth Scientific and Industrial Research Organisation Consult Australia (Formerly ACEA) Engineers Australia Housing Industry Association Master Builders Australia Property Council of Australia Standards Australia New Zealand Department of Building and Housing (observer) Building Research New Zealand Inc (observer) The PCC consists of the following: A senior representative of the ABCB (Chair) A representative of the Australian Government A representative of each of the State and Territory Governments Air Conditioning and Mechanical Contractors Association Association of Hydraulic Services Consultants Australia Australasian Fire and Emergency Service Authorities Council Australian Institute of Refrigeration Air-conditioning and Heating Engineers Australia Housing Industry Association Master Builders Australia Master Plumbers Australia Plumbing Products Industry Group Property Council of Australia Standards Australia 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: Which gutter? 3Nov 08, 2012 9:01 am Thank you SaveH20, you've saved the day once again. I went to the PDF brochure, that's what I was after. I've read it carefully and see what you're saying. The specified QUAD 115 doesn't stand a chance! How can these kit home companies get away with under-specifying something as important as the gutter. And, why has council approved the building application! Who's protecting the consumer and what numskull approved the legislation? I will be phoning today to request an alternative gutter is supplied. Again, many thanks for your assistance. Your time is providing advice on the forum is highly valued. jnk40 Re: Which gutter? 4Nov 11, 2012 8:22 pm It’s not easy choosing which gutter. The QUAD 140 lo-front unslotted is ideal having a 8631mm² cross section, and, would overflow at the front. But, it may not hide the roofing edge, although with only a 5 degree pitch on the awnings it might be OK. The Trimline unslotted has the high front and a healthy cross section of 7800mm². So, it’s not far off what I need and still way better than the QUAD 115 (5285mm²), but, would overflow at the rear. This may not be so bad, as the gutter is away from the house out on the verandahs. SaveH20, can you think of any other pros or cons either way? The plumber says the only drawback of the high fronts like Trimline is they have a tendency to crink/bend when you lean a ladder against them when cleaning etc. The kit home company will supply whatever I want and at no extra cost. Surprisingly, they’re actually interested in how I worked out the calculations. They say they've asked customers in the past which gutter they'd like but the customers usually leave it up to them. Obviously they then just supply the most popular / easiest / cheapest, with no regard to compliance. John P.S. Here is the table and graph from the Lysaght website which were mentioned in SaveH20's above post. Re: Which gutter? 5Nov 12, 2012 6:09 pm Hi John, Everything you say is correct. The Trimline would be ok but then again there are other considerations as you say. Positioning 100 mm downpipes (with 100 mm pops) on gutters at posts 2 & 4 - discussed here on Nov 01 4.48 pm: viewtopic.php?f=35&t=60317&start=40 - will give you very good drainage and it would need a doozy of a storm if the gutters were to overflow unless one of the gutter's walls was very low and/or the gutter was too small. For aesthetics, you want high front gutters but you also don’t want a very low back. You also need 100 mm downpipes for your area's rainfall pattern. The 140 mm wide Lo Front QUAD is a little wider than 140 mm to the roll. It wouldn’t hurt to get a small length and see what it looks like close up and at further distances away. You have to be able to live with it. Half round gutters are very efficient and Lysaght has one that is flat backed. For SE QLD, the back is 87 mm high, the front 103 mm high and it is 138 mm wide. The cross sectional area is 6,568 sq mm. This gutter would be very good and don’t worry about the smaller cross sectional area as the gutter is very efficient plus the downpipes will be in the best possible position as discussed in the other thread. If you won’t be leaning ladders against the Trimline, then these would be very good as well. Most people only get up a ladder to clean the gutters but the half round won’t need that due to the flow characteristics plus the 4 metre run from the high points will allow a good slope. Edited time of referred post. 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: Which gutter? 6Nov 12, 2012 9:46 pm Thanks again SaveH20. Yes, the flat back round unslotted looks a good option. Nice high back, should fit 100mm pops, good capacity, self cleaning & efficient and the front would hide the roof edge. The Trimline's high front would be a problem I feel as I would be accessing the roof more often than not, with aerials, solar panels etc. John Re: Which gutter? 7Nov 15, 2012 11:26 pm Thread visitors should note that the example I posted earlier on how to determine eaves gutter and downpipe sizing compliance for a region's 1:20 ARI by referring to the Lysaght website (tables reproduced by John) is not to be taken as an accurate compliance determination. To do an accurate calculation, AS/NZS 3500.3 and the BCA need to be consulted. The website doc is very basic and a lot of information is not included, for example, there are separate calculations needed for gutters fitted with internal as opposed to external brackets, the roof area multiplier that factors the roof slope is not discussed nor are abutting walls. AS/NZS 3500.3 is a booklet produced by Standards Australia, a private company. It is subject to heavy copyright and is expensive. The information it contains cannot be accessed on the Internet. EDITED: 10/08/2013. Deleted reference to the NCC. 3in1 Supadiverta. Rainwater Harvesting Best Practice using syphonic drainage. Cleaner Neater Smarter Cheaper Supa Gutter Pumper. A low cost syphonic eaves gutter overflow solution. No, I even have sections of narrowness where the tiles won't slide up any further. When I manage some spare time, I might play around with the first DIY part of my… 7 5624 DIY, Home Maintenance & Repair This is a very challenging situation, made much harder by not being on site. Firstly, I think that I originally… 10 10505 Thank you so much. We ended going with the terrain that’s part of our brick. 2 3311 |