Already addressed.
Browse Forums Building A New House Re: Downpipe at facade 21Aug 20, 2021 5:05 pm 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: Downpipe at facade 22Aug 20, 2021 5:16 pm SaveH2O SaveH2O The regulations also factor your roof pitch for wind driven rain and your 24.5 degree roof pitch has a multiplier of 1.23 that determines the roof harvest areas. In other words, 10 sq m is calculated as being 12.3 sq m. Already addressed. Ive got a roof plan area of 133mm2 * 1.23 = 164.21mm2 - total catchment area im stuck with step 3: select eaves gutter catchment area slope factor Im sure step 4 uses 90mm diameter down pipe Re: Downpipe at facade 23Aug 20, 2021 6:57 pm This Practice Note specifies the requirements for roof sizing and calculations for a complete roof drainage system. The figures and contents below provide guidance for: • The steps required when sizing a roof catchment drainage system • Design example of a roof catchment drainage system • Typical types of roof catchment installations • How to calculate roof sizing The following steps are applicable for domestic houses with eaves gutters: 1 Determine the Average Exceedance Probability (AEP) 5% formerly known as ARI 20 years 200 mm/h. Very important to check this because it varies over the Sydney metro area. I have only surmised on probability that you are in a 200 mm/hr area. 2 Calculate the total roof catchment area 164.21 sq m (let's say 165 sq m) 3 Select the eaves gutter design and the slope The slope is the gutter slope.which is a minimum of 1:500 but a minimum of 1:300 is better. The gutter design includes the cross sectional area as shown in the tables. 4 Determine the downpipe size Cross reference tables with the gutter size. 90mm pvc round downpipes are very efficient but they must be painted. 5 Determine the maximum catchment area per downpipe 40 sq m See gutter size. A bigger gutter = draining a larger maximum roof catchment area. EDIT: While Table 3.5.2.2 allows a maximum roof harvest area of 40 sq m, do your calculations to try to have a 30 sq m maximum roof harvest area serviced by each downpipe. This will still retain 6 of the current 7 downpipes plus it will make it easier for a Performance Solution to meet the NCC's Performance Requirements. I also have a feeling that you will be using a minimum size gutter as well. The BCA regs are inferior to the Australian Standards that can be used as a Deemed To Satisfy (DTS) solution and I would never recommend using some of the BCA figures. 6 Determine the minimum number of downpipes required Six. (6 DP x 30 sq m = 180 sq m. Your roof area is less than this.) EDIT: The above figure of 6 is ignoring the BCA mandate to have downpipes at every roof valley. 7 Determine the catchment area per downpipe (165 (sq m) ÷ 6 (downpipes) = 27.5 sq m average roof harvest area. 8 Determine the most advantageous downpipe positions Middle of the back wall needs to be a high point as it already is but the two downpipes need to be moved closer to the front so the catchment for each downpipe is at least 29 sq m. 9 Select an overflow provision An emergency overflow provision that is designed to cope with a 1:100 ARI is required. Not your concern. 10 Apply to the roof catchment drainage system to the building plan Show to builder. The BCA also has a reg that states a downpipe must be fitted near a roof valley, tha Australian Standards AS 3500.3 do not state this.The NCC is performance based and not set in stone, other referred Standards can also be called up as Deemed To Satisfy (DTS) solutions. The builder can 'call up' either singularly or parts of AS 3500.3 as Deemed To Satisfy (DTS) solutions and incorporate i use into the BCA regs or even produce a Performance Solution that does not require the downpipe. 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: Downpipe at facade 25Aug 23, 2021 8:09 pm As of now, this is the builder's reply: As mentioned, the options for this downpipe, are limited to either:
We feel the downpipe must be installed for the following reasons:
We have had three of our architects, & our hydraulic engineer brainstorm this for you & they all agree the downpipe is required. We welcome yours, & your consultants, advice & recommendations but this didn’t really provide an answer & doesn’t address the obvious 12m requirement between downpipes. At the end of the day, we want to do the right thing by you, & for your home to work properly, so from (THE BUILDER) perspective the porch downpipe is not negotiable….. it’s a “must”. Having said that, I can see your heart is set on removing the porch downpipe, & there is now enough history to determine this is your preference. Assuming you accept responsibility for this choice, we will remove this downpipe. In order to do so, we will provide a waiver for you to read, accept & sign. There will be some warranty obligations for you to take on, & these obligations will be documented, so as to relieve (THE BUILDER) from future warranty claims from both yourself, & future owners of the property. I cannot emphasize enough, how much (THE BUILDER) DO NOT recommend removing this downpipe, but it is your home after all. Please let us know what you wish to do, we will get the plans updated as required, so we can start moving forward again. We dont know what to do now. If we fight this or not. This forum is all we've got Re: Downpipe at facade 26Aug 24, 2021 12:44 pm It is 115mm quad. I am 'somewhat' surprised that Ace don't make a 125mm quad gutter as I have thought that 125mm would be the standard fitting in NSW. It must be remembered that the 1:20 ARI figure is the minimum average rain intensity over a 5 minute period, a 1:20 ARI will always exceed this intensity and minimisation should be avoided but having said that, the builders current design that uses 7 downpipes has a huge inbuilt 'safety margin' with small roof areas harvested which is commendable. I have been unable to find a specification sheet on the ACE Gutter website that gives the 115mm quad gutter's effective cross sectional area although a diagram does state a volume of 6.2 litres per metre to the height of the overflow holes. Like ⋅ Add a comment ⋅ Pin to Ideaboard ⋅ The effective cross sectional area is however measured not less than 10mm below the overflow which in this case are the overflow slots. This means that the Ace 115mm quad's effective cross sectional area may be 6,200 - 1150 = 5,050 sq mm. (115 x 10 = 1150). It is highly unusual to not publish a gutter's cross sectional area. EDIT: The above effective cross sectional area is found in AS/NZS 3500.3 but not referenced in the BCA. To drain up to a 40 sq m roof harvest area in a 200 mm/h ARI area and as per NCC Table3.5.2.2 you are required to have either a gutter Type A or C as per Table B. Gutter Type A is a Medium Rectangular Gutter with a cross sectional area of 6,500 and Type C is a 115mm D gutter (quad) with a minimum cross sectional area of 5,200 sq mm. The regs allow a gutter cross sectional size to be taken to the nearest 100mm but your gutter's cross sectional area could be short of the required minimum as per Table B. You cannot be a little bit pregnant even when the plan design is superior. It is important to check your denoted 1:20 ARI. I have used 200 mm/h as your guide to compliance but I don't know the exact area you are building in and the builder may have used the more area specific IFD calculation. You should try to accomodate maximum roof harvest areas of 30 sq m even though compliance allows for 40 sq m. This can be done with 6 downpipes. boang As of now, this is the builder's reply: We feel the downpipe must be installed for the following reasons:
We have had three of our architects, & our hydraulic engineer brainstorm this for you & they all agree the downpipe is required. We welcome yours, & your consultants, advice & recommendations but this didn’t really provide an answer & doesn’t address the obvious 12m requirement between downpipes. I have previously advised the following: The current NCC regulatiions state: 3.5.3.5 Downpipes — size and installation Downpipes must— (a)not serve more than 12 m of gutter length for each downpipe "Not serve more than 12 m of gutter" means the total length of gutter that drains the roof harvest area between the high points to a downpipe which also takes into account the maximum allowable roof area drained. This requlation allows for example a veranda having a gutter 24 metres long to have downpipes at the ends (24 m apart) with the high point mid way. boang
The fall to either downpipe would be no more than nine metres if the high point between the two front downpipes is at B1 nearest left front corner (an approximate 9 m gutter length to the sitting room downpipe). The regulatory minimum slope of 1:500 over 9 m is a fall of 18 mm and so a more effective slope of 1:300 would provide no street scape aesthetic detriment. It should also be noted that the two downpipes at B4 and B3 on the plan already show an intended length of gutter about 9 metres long. If worse came to worse, just fit one of our Gutter Pumpers! boang
I assume they mean a "spreader" attached to a downpipe. Not sure if the BCA regs also include the wall abutting the garage roof as a catchment during wind driven rain like the AS does. The garage roof plan area looks to be a bit less than 13 sq m. By having the gutter high point near to the B1 front left corner (about 3.7 m from B1 downpipe), the roof harvest area drained to the spreader should be about 14.5 sq m, no more. This would not compromise the garage roof drainage and would be well within compliance. boang We have had three of our architects, & our hydraulic engineer brainstorm this for you & they all agree the downpipe is required. We welcome yours, & your consultants, advice & recommendations but this didn’t really provide an answer & doesn’t address the obvious 12m requirement between downpipes. There is NO 12 m requirement between downpipes. The BCA does have a requirement for a downpipe at each roof valley (the AS doesn't!) but they have omitted one from the plan...it seems that you can in fact be a little bit pregnant! Right Wall High Points 6.6 m from top wall. The left wall high point will also correspond. Next high point to be at corner that is about 7.3 m down from first high point. 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: Downpipe at facade 28Aug 24, 2021 1:26 pm Sounds like they don't like admitting they don't know the appropriate regulations or how DTS and performance Solutions work. EDIT: I just checked the BCA (Part 2 of the NCC) and they do not state any required distance under the gutter slots nor do they reference the AS for same when calculatimg the gutter's effective cross sectional area. Looks like whoever published the regs knew nothing about hydraulic jumps etc. The ACE 115mm quad gutters meets compliance. The BCA roof and stormwater drainage regs are sub standard. Here in Victoria, the BCA has for good reason never been adopted as a DTS provision for roof drainage systems. 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: Downpipe at facade 29Aug 24, 2021 2:41 pm boang Ive got a roof plan area of 133mm2 * 1.23 = 164.21mm2 - total catchment area I just realised that this includes the garage roof. Anyway, this isn't really important as you only need to concentrate on the house roof and its 6 downpipes.Just minimise as much as you can the amount of water draining to the two front downpipes. 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: Downpipe at facade 30Aug 24, 2021 4:22 pm boang Thanks SaveH2O, I tell them exactly everything you say and propose including the standards yet they dont take it or consider it. I really dont know what to do to convince them. they did consider it and they've offered to remove it for you if you indemnify them from any damage resultant from the removal of the downpipe. I think if you want to protect your warranties you're going to either accept their original plan or do more than run messages back and forth on the forums. SaveH20 is ultra knowledgeable, but you're now venturing into a level of involvement that would be considered paid consulting work by many. Dark matter scientist, can breathe underwater, mind reader and can freeze matter just by willing it. Trust me, its in my sig. Re: Downpipe at facade 32Aug 24, 2021 6:44 pm Yes but I would try to have HP 3 closer to D3 but more importantly have HP 5 closer to D6 to reduce the volume of water discharging to the garage roof. 14.3 m between the two front downpipes has been their objection and despite the builder quoting non existent regulations, it is a lot of guttering with corners which slows flow, the reason I would like to see DPs 3 and 6 harvest lesser roof areas despite having efficient round downpipes. If only the water coming off a valley could be discharged towards the downpipe. 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: Downpipe at facade 34Aug 24, 2021 8:13 pm Looks good. I think D3 was a tad closer to the corner on the original plan. The shorter the gutter length, the better. Maybe also paste the "serve no more than 12 m of guttering" reg below the update. 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: Downpipe at facade 35Aug 24, 2021 8:32 pm SaveH2O Looks good. I think D3 was a tad closer to the corner on the original plan. The shorter the gutter length, the better. Maybe also paste the "serve no more than 12 m of guttering" reg below the update. Yeah I'll emphasize "serve no more than 12 m of guttering" because they keep emphasizing "to comply with the NCC (minimum 12m between downpipes, with a recommendation to have downpipes as close to valleys as possible)" which is not stated in NCC there is no "between" word stated in the NCC i dont know why they keep pushing it Re: Downpipe at facade 36Aug 24, 2021 11:57 pm They have re-worded that particular regulation a few times now, it was "between" at one stage in the now distant past. The NCC does state "downpipes close to valleys" but AS 3500.3 which is an accepted DTS solution doesn't. It is often ignored anyway because building surveyors don't know and they just accept the plumber's Certificate of Compliance as proof of compliance lol. This practice is an endemic failing within the system. The BCA also lists State and Territory specific additions and variations, the NSW ones start on page 425. These should be cross referenced when checking regulations and Standards and also looked for in the general text. The similar house in the photo you posted may have had bigger gutters and small roof harvest areas which allowed them to use the AS as a DTS solution or they may have just ignored the NCC reg. It might also be an ex display home. Architects often draw downpipes in nominal positions and leave it up to others (plumbers) further down the food chain to fit them in the correct position for compliance but this is rarely done because they are not paid to do it and many don't know/support Best Practice in any case. The importance of street scape on display homes will invariably see no downpipes fitted at the front and display homes often have non compliant roof drainage. A NSW display home roof drainage compliance blitz during the early high fronted gutter fitting debacle saw most display homes the DFT inspected fail compliance. I'll post a link to the NSW Parlimentary report. It remains an interesting read. https://www.gutterpumper.com.au/files/H ... report.pdf If you are going to have a water tank, check with me on here first because practically everyone ends up with a sub standard system. BTW, you have probably realised before now that my early replies were made in the belief that the house was already built and the guttering and downpipes fitted. I should have asked rather than assume. I think that some of my comments re removing the downpipe and resloping the gutter may have confused you. 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: Downpipe at facade 38Mar 29, 2022 10:24 am beetleone @boang did you end up moving the downpipe ? I just saw this thread Hi beetleone, Nope we didnt, as the builder will end up having us signed a document that keep them clean if ever something happens with the downpipe or gutter having problems Re: Downpipe at facade 39Apr 29, 2022 9:31 pm boang beetleone @boang did you end up moving the downpipe ? I just saw this thread Hi beetleone, Nope we didnt, as the builder will end up having us signed a document that keep them clean if ever something happens with the downpipe or gutter having proble oh i see, which builder? Building Standards; Getting It Right! It's all good. You can get both wye piece and the coupling with or without thread. The cost difference is negligible and means the plumber only has to carry the single… 1 4897 Dear Members I have to decide the Facade column size. My custom builder standard is 350mm with rendering, but i asked for 470mm plus stone or tiles and yet to get… 0 7493 |