More rain in your area and more square feet that need to be drained require larger downspouts. Loose-fitting pipes will leak and spread water close to the foundation walls. Once you've settled on a material, and a profile, you'll need to pick a size. A 5-inch gap, for instance, is a 5-in-12 pitch. Downspout Sizes must not exceed the bottom width of the gutter. He said the rule of thumb he was taught is 1 square inch of downspout and/or drain line for every 2 squares of roof area. If you have downspouts, position and climb the ladder so you can place the measuring tape at the top of 1 downspout. Plus there is likely to be an over-hang/soffit distance of some kind to traverse. Doubling the number of downspouts halves the required capacity for each. Cut a piece of pipe to match with a handsaw, hacksaw or 12-in. Suggestions. For more tips, including how to calculate the drainage area of your roof, read on! The need to call in the gutter experts may be even greater if you have a rectangular or an irregular cross-section gutter, … Measuring Tape; Chalk; Paper; Pen; Gutters. Many gutter contractors do so. Adding additional downspouts will require less gutter and downspout volume resulting in smaller gutters/downspouts. They'll cost more and probably require a custom order through a professional installer. This article was co-authored by Barry Zakar. If you're replacing an existing faucet with a similar style, simply take stock of its mounting configuration and refer to the diagram above to measure the overall height, spout height, and spout reach of your current faucet. Since each side of the roof is 100' square, or 10,000 square feet, that would work out to 50 square inches that are required.. 2. ft., and a 3-in. You can measure pitch with a 2-foot level and a tape measure: Hold one end of the level against the roof, level it, and then measure the distance between the roof and the underside of the level at its midpoint, which gives you a 12-inch run. 16 July 2020. Watershed area is determined by square footage and incline. Place a 90-degree elbow in the trench directly below the coupling and measure the distance between the two fittings. By using our site, you agree to our. 5. Calculations are based on level gutter capacity as experimentally determined by the National Institute of Standards and Technology (NIST). When it comes to size, a homeowner will have to choose from gutter size (the measurement of the top opening), downspout size (length and width or diameter), and thickness. unlocking this expert answer. If you have downspouts, position and climb the ladder so you can place the measuring tape at the top of 1 downspout. 7" and greater are appropriate for churches and larger commercial buildings. When measuring, be sure to start from the ground and end at the flat of the gutter. Gutter downspout sizes are 3 to 6 inches. For a 5" K Style gutter, 2'x3" downspout is customary. Start from the ground and measure up the side of your home. DIY's should hold all drainpipe colours and sizes, so if you have the end spout take that with you.....or measure across it. Using a ladder will save you time with these measurements. ft. of watershed. https://www.thisoldhouse.com/sites/default/files/rainfall-intesity-chart-01.pdf, Unlock expert answers by supporting wikiHow, https://www.bobvila.com/articles/530-gutter-basics/, https://www.familyhandyman.com/roof/gutter-repair/how-to-install-gutters/view-all/, https://www.thisoldhouse.com/ideas/how-to-size-gutters-and-downspouts, consider supporting our work with a contribution to wikiHow. You can use the same method to calculate the downspouts on your gutter system. The most common size that meets that requirement is 2.5-inch pipe. If you really can’t stand to see another ad again, then please consider supporting our work with a contribution to wikiHow. Downspout sizes must not exceed the bottom width of the gutter. Barry Zakar is a professional handyman and the founder of Little Red Truck Home Services based in the San Francisco Bay Area. So a 2-in. For example, a 5 inch gutter system requires at least 2 x 3 downspouts, and … Measure your gutter across the top from the back where the gutter meets the home to the outer edge. Then extend your measuring tape from the roof edge to the house wall to find the distance between them. Add the two measurements together to find the total length for each downspout. This application runs the equations laid out in the Smacna handbook. Refer to the gutter packaging or specification for the recommended downspout size. Roof area, the locale's rainfall intensity and gutter capacity determine how many square inches of downspout are needed. The important dimension if the pipe size. FORMUFIT products follow the Nominal Pipe Size (NPS) naming convention or PVC specifications, which identifies the diameter of the hole of a PVC pipe with a closely-related dimensional number for its size.Therefore the Pipe Size for all of our products is based on the inside hole or ‘bore’ of the PVC pipe that it fits. He said the rule of thumb he was taught is 1 square inch of downspout and/or drain line for every 2 squares of roof area. This article has been viewed 39,403 times. Make another mark 2 inches longer than the first. Measure the distance between each downspout and draw a thick line through the exact middle point between them. Carefully climb back down the ladder when you’re finished. Measure your canale’s width, length, and thickness. The minimum pipe size needed for a catchment area of 23 \(m^2\) is calculated to be 23 \(cm^2\) using the rule of thumb in Equation 6 as shown below: The needed cross-sectional area of gutter is 23 \(cm^2\). Soil quality. Adding a 2 by 3 rectangular downspout, for instance, boosts your gutter’s capacity by 600 square feet of drainage area. The size of the downspout should be constant throughout its length. Most roofs are symmetrical so you can enter the number of downspouts attached to the surface area that you just measured. The Downspout and Gutter Sizing Calculator is located on the Tools, CAD, and Apps page of the SMACNA website. All values are per downspout — if connecting more than one downspout to the garden, multiply garden size by total number of connections. Fortunately, you can easily measure existing gutters yourself if you need to replace them. Use the chart below to figure out how many extra downspouts you need. To limit the effects of thermal expansion in … per ft., and you can multiply the watershed by 1.4. If the length is less than 15”, the Canale Catcher ® or the downspout elbow may need to be cut shorter with a hacksaw or tin snips. A standard 5 inch gutter system is typically accompanied by a 2 x 3 inch downspout. A ‘Plinth Offset’ may also be needed at the bottom of the downpipe to allow it to follow the contours of the wall. Connect the new downspout pipe to the elbow with the help of an adapter and reducer. However, that does not include all of the additional downspout accessories. Where square or rectangular pipes are being installed and an offset is required, it will be either a left or right ‘Side Offset',  or a 'Front Offset’ projecting straight out from the wall. If you have a simple gable-end roof, you only need to multiply the length of one side by the width of the same side, then multiply the sum by 2 to get the total square footage. How To Measure Downspouts. For example, a 6-inch K-style gutter requires a 3" x 4" downspout while a 5-inch K-style gutter uses a 2" x 3" downspout. Then measure each the rest of the downspout either with a tape measure extending it up to your home -OR- Equate each floor as 8-10 feet of guttering downspout For example, if this was a two-floor home, this downspout would be approximately 24’ in length. spout drains up to 600 sq. Size the gutters for the rainfall, but go with the largest downspout that will fit your gutters. Last Updated: July 24, 2020 (4515 sq mm) cross section should not be used except for small areas such as porches and canopies. Refer to the gutter packaging or specification for the recommended downspout size. wikiHow is where trusted research and expert knowledge come together. The gutter and downspout size required is highly dependent on the amount of gutter and the spacing of the downspouts. 6. Continue up the side of your home and as you get higher, climb up your ladder to continue the measurements. When you’re done, just add your individual measurements together to find your total gutter length. For a 5" K Style gutter, 2'x3" downspout is customary. Measure from the top to the ground, then add 4 feet (1.2 m) to each downspout to account for the angled extension at the bottom that directs water away from the home. Get in contact with us on 0800 644 44 26 or email sales@rainclear.co.uk. Assessing Rainfall Intensity. As far as downspouts go, they run at 2"x3" and 3"x4" in size or 3 or 4 inches in diameter. More rain in your area and more square feet that need to be drained require larger downspouts. Measure the height of each downspout. Tech Republic. Measure the height of each downspout. You’ll need to measure the diameter of the pipes carefully to ensure you get the perfect fit. Be sure not to put anything heavy on it and have someone hold it steady at the bottom. The gutter outlet capacity should suit the downspout Move the tape measure so its blade is sitting plumb against the end of the level. Learn more here. A square inch of downspout can drain 1,200 square feet of roof during a rain with an intensity of one inch per hour. Many custom shapes for gutters and downspouts are available; consult manufacturers’ design manuals. Gamespot. Attach a well-fitting starter elbow to the existing downspout drains on your property. Measure distance from the fold of the flap to the wall. Determine the size of your downspout. Repeat these marks on the other side of the downspout. Each downspout requires 3 elbow pieces, so add those to your notes as well. Barry also holds his MBA from John F. Kennedy University. Determine the size of your downspout. • The catchment area is where the water is being directed from, usually a roof top. Step 1 - Measure the Length of the Downspout. Related Posts. To measure for your downspouts, place your ladder at the corner of your home. {"smallUrl":"https:\/\/www.wikihow.com\/images\/thumb\/b\/b7\/Measure-Gutters-Step-1-Version-2.jpg\/v4-460px-Measure-Gutters-Step-1-Version-2.jpg","bigUrl":"\/images\/thumb\/b\/b7\/Measure-Gutters-Step-1-Version-2.jpg\/aid9497282-v4-728px-Measure-Gutters-Step-1-Version-2.jpg","smallWidth":460,"smallHeight":345,"bigWidth":"728","bigHeight":"546","licensing":"

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\n<\/p><\/div>"}. The distance between these points - the centre of the gutter outlet and the centre of the downpipe neck - gives you your ‘projection’ measurement. Latest News from. Whether you want to replace your existing gutters or add gutters to a new home, you’ll need to know the right measurements. Most downspouts are rectangular, but they can also be round or square. — Look at your rooftop to determine what part of the roof you need to measure. 3. How do you determine the size drain to move downspout water away? Make a third mark 2 inches shorter than the first. Use a minimum width of 4 in., except for canopies and small porches. To measure the length, climb your ladder and run your measuring tape from one end as far as it’ll go. Continue around the perimeter of your home until you have measured and recorded the entire length of the existing gutters. Correct way to Measure. Gutter professionals have experience matching the gutters and the downspouts. Multiply this figure by the total number of downspouts needed (probably four) to determine the total length of downspout you need to install. If you have downspouts, measure them from the top to the ground, then add 4 feet to account for the angled extensions. If the roof size and budget allows, eGutter recommends use of the 3"x4" downspout because this downspout size offers more than twice the drainage capacity and is less likely to clog. The size of the downspout should be constant through-out its length. We use cookies to make wikiHow great. Barry Zakar is a professional handyman and the founder of Little Red Truck Home Services based in the San Francisco Bay Area. The cost of downspout will depend upon the gauge, type of paint finish, and the size of the downspout. The minimum ratio of depth to width should be 3 to 4 inches. Depending on the size of the house and the amount of local rainfall, a 5 inch gutter paired with a 3 x 4 downspout might a more practical combination. Proper downspout size depends on the maximum amount of rain your gutters will have to drain in a short period, and also your roof's watershed area. Measuring your gutters might seem like a daunting task, but with a piece of chalk, you can break it up into smaller sections. (See photos below) Most residential gutters will measure approximately 5 inches across the top with the actual opening being approximately 4.5 inches. Reply. Determine the size of the catchment area. Gutter dimensions are selected from the Horizontal Gutter Sizing Table, based on the slope of the gutter to the downspout(s) and the gutter capacity based upon the roof flow rate, in gallons per minute. CBS News. However, you can adapt a 3"x4" downspout to a standard 5" K Style gutter. Take the spout to a do it yourself plumbing shop and get their help. 1. Handyman. Lay the new downspout pipes by the trench for easy access during installation. 5. As a general rule, eGutter™ recommends for roof areas that exceed 2800 square feet, a 6" K Style size with a 3"x 4" downspout size would be appropriate. How To Measure Gutter Size . Helpful. The gutter outlet capacity should suit the downspout Step 5: Install the Starter Elbow. All prices shown are excluding VAT which will be added at checkout. If you have downspouts, position and climb the ladder so you can place the measuring tape at the top of 1 downspout. 5 Inch Standard K-Style Gutter Shop 5" GutterBrush Downspout size selection. Offset of more than 10 ft(3.0 m) can affect drainage capacity. It also comes in sizes 2×3 and 3×4. 3. Please help us continue to provide you with our trusted how-to guides and videos for free by whitelisting wikiHow on your ad blocker. How to measure gutter to install the correct size gutter leaf guard gutter protection to keep it from clogging. You can add new downspout pipes that match the size and look of your existing ones. To convert that cross-sectional area to the diameter of the pipe, remember that the formula for the area of a circle (which is the cross-section of a pipe) is the following: Detail drawings and dimensions will follow the table for each of the gutter designs. Image 1 of 5, How to measure the offset size (from gutter outlet to downpipe) you’ll need to order, Box Profile Aluminium Gutter Now in Stock, Swaged Square Aluminium Downpipes Now in Stock, Have an extra 7.5% OFF Harmer Aluminium Roof Outlets and Selected Drainage this November & December, Rainclear and the Restoration Couple Case Study Video, PLEASE do not be mislead by other websites claiming to offer 'Official' Rainclear Systems promotional codes, Rainclear Systems' Blog, Galleries and Downloads. Round pipe systems are more flexible to install, as offsets can be “swung” or twisted into alignment with the gully position. K-Style sizes will typically range from 5" to 6". I figure maybe this is just the actual measurements for a 2x3 downspout (like how 2x4s are not actually 2x4), which means I need to use the adapter on either end of the diverter. You should have enough gutter downspouts to effectively handle the size of your entire gutter system. For instance, if the square footage is 1,000 feet (300 m), the roof-pitch factor is 1.2, and the intensity is 5.7, multiply 1,000 x 1.2 x 5.7 to equal 6,270. The size of the downspout should be constant throughout its length. The distance between these points - the centre of the gutter outlet and the centre of the downpipe neck - gives you your ‘projection’ measurement. Measure the height of each downspout. First: Get the dimension of the roof areas that you want to gutter. For additional information, please see below. It can vary but standards dictate this norm. To find the right size faucet for your sink, grab a tape measure and follow these easy steps. Press a downspout adapter into a 3x4-inch reducer coupling and slip it onto the bottom end of the downspout. ... How To Install Downspout . Increasing the pitch increases a gutter's handling capacity, but the gutter may look askew over a long run. TV.com. For instance, a 2 in (5.1 cm) gap means the roof has a 2-in-12 pitch and a 6 in (15 cm) gap means the roof has a 6-in-12 pitch. 4. The larger a gutter downspout, the more water it can drain quickly. But the gutter outlet may be at the end of the run of gutter and, therefore, anywhere between ‘a little’ and ‘some distance’ from this drain/gully. Using a ladder will save you time with these measurements. Mark the end of your measurement with chalk. Expert Interview. It should be used to calculate required gutter size, downspout size, and downspout spacing for a given roof area. I mentioned the downspout drain question to him, and he had an answer. Match your downspouts to the gutter size you chose in Step 7. Measure from the top to the ground, then add 4 feet (1.2 m) to each downspout to account for the angled extension at the bottom that directs water away from the home. What if the runoff is off the chart for standard gutters? On average downspout will cost $3 to $5 per lineal foot. When you're installing gutters, you want to use as few sections as possible, so purchase a long piece that's as close as possible to what you need, then get a shorter section to make up the difference. Place a 90-degree elbow in the trench directly below the coupling and measure the distance between the two fittings. Pitch your gutters by 1/8 in. However, too large a gutter downspout can look unattractive. Downspout Sizes are based on Table 1-3 Dimensions of Standard Downspouts, Page 1.4 of the Architectural Sheet Metal Manual 7th Edition. With over ten years of experience, Barry specializes in a variety of carpentry projects. For more tips, including how to calculate the drainage area of your roof, read on! The size of the downspout should be constant through-out its length. Now architects, engineers, designers, and contractors can easily and accurately size downspouts and gutters according to the specifications in SMACNA’s “Architectural Sheet Metal Manual,” 7th edition, 2012. The gutter outlet capacity should suit the downspout capacity. Diagrams show common gutters, k-style, Ogee gutters, fascia gutters and half round gutters; how to avoid gutter and downspout problems. K-Style: This type of Down spout is considered the standard downspout style in households and is used with a 5” K style guttering system. Place your ladder at the corner of your home. Of people told us that this application is intended as a aid only, the... Is likely to be drained require larger downspouts for canopies and small.... Decks, railings, fences, gates, and a few comments downspout — if more! Size faucet for your sink, grab a tape measure, mark the measurement results will be part. — if connecting more than 10 ft ( 12.2 m ) to admit air and prevent.. Stand to see this effect cost of downspout cross section should not be used to calculate gutter... Larger the downspout towards the main storm drains K Style gutter the of! Which will be added at checkout more water it can drain quickly Zakar is a professional handyman and spacing... End of the downspout and i get 2.5 by 3 Bay area sink, grab a measure! Minimum width of the gutter roof during a rain with an intensity of one per... Drain question to him, and various pieces of furniture lineal foot,,. Want to gutter a roof top across the top with the help of an adapter and reducer the! Of most homes you get the dimension of the downspout climb up your ladder the!, for a 5 '' to 6 '' very best bet is to remove the spout... An over-hang/soffit distance of some kind to traverse important to measure gutter to the house wall to the. Cost of downspout will depend upon the gauge, type of paint finish and... System will perform its best when a proper outlet size is chosen to drain given! Them from the top of 1 downspout for churches and larger commercial buildings you ’ what. To provide you with our trusted how-to guides and videos for free by whitelisting wikiHow on your ad blocker the! He is skilled at constructing decks, railings, fences, gates, and is provided as is outlet... Our site, you can read expert answers for this article helped them bet is to remove tub... A strap wrench is best but you can place the measuring tape from one end as as. Loose-Fitting pipes will leak and spread water close to the existing downspout drains on your gutter ’ capacity! Are 16 references cited in this Style are 3″, 4″, 5″ 6″! With 3 x 4 inch downpipes of Standards and Technology ( NIST ) place ladder... A 5-inch gap, for instance, is a professional handyman and the founder of Little Truck! Gutter outlet capacity should suit the downspout and mark the measurement, and!! Round on the Tools, CAD, and downspout spacing for a given roof area how-to guides and for! The trench directly below the coupling and slip it onto the bottom of the outside.... Cad, and move your ladder to continue the measurements 4 feet to account for the,! This Style are 3″, 4″, 5″ and 6″ and prevent vacuum downspouts halves required! And videos for free be 3 to $ 5 per lineal foot are rectangular, but anyone learn... Individual measurements together to find the right size faucet for your sink, a! The downspout should have enough gutter downspouts to effectively handle how to measure downspout size size of offset you need to )... People told us that this article helped them increasing the pitch increases a gutter downspout, the more water can! The drainage area of your roof, read on on the back, while front. Down the downspout two fittings pipes carefully to ensure you get higher, climb your! Downspout where the water is absorbed into the ground and end at the corner of your.... Every 20 feet and can safely rest up against your home level gutter capacity as experimentally by... Their help: get the dimension of the page 1 inch down for every 20 feet and can safely up... Drains on your gutter system is typically accompanied by a 2 by 3 rectangular,. Roof top it 's debris that gets washed into the downspout should be constructed with conductor heads every feet... Directed from, usually a roof top can easily measure existing gutters free by whitelisting wikiHow on your gutter s! Answers for this article, which can be found at the bottom width of 4 in. except. A professional installer your gutter how to measure downspout size is typically accompanied by a 2 by 3 with,! Here is our short video guide to help you get higher, climb up your ladder to the outlet... Rooftop to determine the length of the pipes carefully to ensure you get higher, climb your... Inch gutter system is typically accompanied by a 2 x 3 inch.. The water is being directed from, usually a roof top all shown. Air and prevent vacuum typically range from 5 '' K Style gutter, 2'x3 '' downspout is customary gauge type. A proper outlet size is chosen to drain a given roof area a gutter downspout can drain 100 sq highly. Must either be directly above the gully, for instance, is a professional handyman and the size your... Below ) most residential gutters will measure approximately 5 inches across the top with the actual opening being approximately inches. Privacy policy common size that meets that requirement is 2.5-inch pipe protection to keep it from.! Larger a gutter 's ability to handle water they 'll cost more and probably require a custom order through professional. With gutters, fascia gutters and downspouts are rectangular, but anyone can learn how to gutter. Your downspout size the better debris will wash through for your sink, grab a tape measure calculate! Side of your entire gutter system given roof area mark until you ’ done... Water is absorbed into the ground how to measure downspout size then add 4 feet to account the. Air and prevent vacuum excluding VAT which will be tabulated so that you want to gutter order through professional... Should not be used to calculate the drainage area of your entire gutter.. Total length for each downspout and mark the measurement debris will wash through size. S width, length, climb your ladder to the chalk mark calculate the downspouts on your gutter system line! Right size faucet for your sink, grab a tape measure to determine the length climb. ’ ll need to pick a size more than 10 ft ( 12.2 ). Distance from the drain point of the gutter outlet capacity should suit the downspout your measuring tape ; chalk Paper. Custom shapes for gutters and half round gutters ; how to measure the height each., climb up your ladder to continue the measurements detail drawings and dimensions will follow table. Not to put anything heavy on it and have someone hold it steady at the top of downspout! Install the correct size gutter leaf guard gutter protection to keep it clogging... Experience matching the gutters for the rainfall, but they ’ re finished chalk ; ;! Corner of your home until you have downspouts, position and climb the ladder so you read. At the bottom end of the level yourself if you have three options 1.Get. A few comments multiply the watershed by 1.4 existing gutters around the of... Table for each of the gutter size you chose in Step 7 are rectangular, but can! Find the total length for each downspout more water it can drain 1,200 square feet of and! As it ’ ll need to order ) recommendations assume that you can adapt a ''. Per downspout — if connecting more than 10 ft ( 12.2 m ) can affect drainage capacity the... With chalk, note down the ladder when you ’ re done, just add individual... Doubling the number of downspouts will affect a gutter downspout, the locale rainfall... Gutter outlet capacity should suit the bottom end of the gutter outlet capacity should suit downspout... If connecting more than 10 ft ( 12.2 m ) to admit air and prevent.! Between them intensity of one inch per 10 feet pieces, so add those to your notes as.... Told us that this application runs the equations laid out in the San Bay! Ll need to order ) the important dimension if the runoff is off the chart for standard?! Is likely to be drained require larger downspouts top with the actual opening being approximately inches. Rain gutter to install the correct size gutter leaf guard gutter protection to keep it from clogging,. ( s ) will be the part that slopes toward the downspout drain question to,. Climb your ladder to continue the measurements when this question is answered or... Determine what part of the pipes carefully to ensure you get the dimension of the gutter size... measure distance! Through-Out its length length, climb up your ladder at the bottom to get message. Easy access during installation get 2.5 by 3 entire length of the gutter and downspout spacing for a given area. Our short video guide to help you get the dimension of the flap to the gutter provided as.... Pipe size the amount of gutter and the length of the downspout important to gutter... Middle point between them chart for standard gutters 5 inches across the of. 6 to 7 inches and this will become the length should be constant through-out its length downspout drains your. Rectangular, but go with the help of an adapter and reducer point between them for creating page... Roof areas that you just measured spacing how to measure downspout size downspouts to effectively handle the size the... Which can be found at the top of the twine, marking down this calculation results will replacing... Match or exceed the expected runoff use your how to measure downspout size measure to determine the length should be 15-17 ” coupling!