Purlins can also protect the roof decking from being blown away by strong winds. For instance, you can space the metal purlins further apart if you use stronger purlins. Solid decking, such as plywood, OSB, or dimensional lumber with closely spaced joints, can be installed over treated lumber to cover it. How Far Should Purlins Be Positioned On Sloping Roofs? However, it is an excellent option to be recommended for times of low-budget construction. The purpose of the underlayment is largely that it is required by code. Supported purlins will strengthen your roof regardless of its pitching. This heavy, smooth paper will protect the felt from the metal sheeting. Roofing purlins are placed over principal rafters, building walls, or steel beams. Building owners can extend the lifespan of their new roof and save the expense of a roof tear-off by having roof contractor Pasadena install metal roofing over existing shingles.. If galvanized steel or stainless steel is used as a corrosion-resistant coating on treated lumber, it can be used on galvanized metal. Due to the exceptional features of a vapour barrier, it is advisable to install them to better work with other equipment. On most projects, there are two types of underlayments needed. Both Z and C purlins are arranged vertically on roofs to facilitate easy installation and fabrication. They are commonly used in metal structures to tie rafters on the roof to enhance the stability of the building. The first goal of roofing underlayment is to keep the roof deck dry before installation of the metal roofing material. Galvanized metal should not be used with untreated lumber because it does not provide corrosion protection. The first is the climate. Two rafters, each running from the opposite side of the house or room, typically meet at the apex of the room and are held together by ceiling joists or rafter ties, forming a basic truss. Leave gaps between panels. Apply continuous air control membrane to existing roof . A large portion of them needs repair. They also help make your entire roof structure more rigid. It can also provide protection if there should be a roof flashing occasionally bleed some water. If you have a very heavy roof, youll want to use a harder wood so it doesnt crack under the weight. This is more expensive but will also be higher quality. In architecture, structural engineering or building, a purlin (or historically purline, purloyne, purling, perling) is a horizontal beam or bar used for structural support in buildings, most commonly in a roof. For example, purlins should be placed eight feet from 24 struts and six feet away from 26 struts. Install purlins on top of your roofs rafters along with a felt underlayment for maximum support. If you are considering using pressure treated purlins under a metal roof, there are a few things you should know. Quality management system: ISO 9001:2008 International Standard. When dissimilar metals react with one another, such as wood and copper, their chemical reactions cause them to rust. There are a few things to consider when choosing what wood to use under a metal roof. The products are ensured to be shiny and beautifully patterned. Run off from, or contact with, materials which are incompatible with zinc should be avoided. I'm in Blacksburg VA if that helps. Florida Product Approval # 4595.18. In general, however, it is generally not recommended to install galvanized roofing on treated lumber due to the potential for corrosion and other issues. By tradition, purlins are arranged depending on the direction of the roofing slope. Erythematics is the substance that transports water. If youre looking for lumber for use in decking or railing, use kiln-dried softwood. Tables are given for 5 or more spans. If not, a vapor barrier behind it would be wise. Purlins are of two types, steel or wooden; steel purlins are more effective than wooden purlins due to their unmolded features, whereas wooden purlins can get fuzzy or mouldy over time. In terms of arrangement, we can have single spans with staggered sleeved/butt arrangement, single/double span with staggered sleeve arrangement, double span butt joint system, and single span butt joint system. Moreover, wood gets moist quickly, which leads to unwanted smells and the risk of sagging. Yes, underlayment should be in place. This standard measurement should give you the approximate number of purlins you need for your project. Line up the blue lines of the underlayment. The run system determines the selection of a purlin. but when compared to synthetic underlayment, this underlayment fails to provide such long years of life. Taking on different home projects is something Arthur Callahan is passionate about. Purlins are critical when installing a metal roof. Moreover, the moisture can add significantly to the weight leading to sag. Your roof will enable you to choose from 12 gauge, 14 gauge, and 16 gauge purlins. It will make installation harder in my view. If you do, i suggest the underlayment on top of it. Choosing the right underlayment for your roof can be a difficult decision. Steel purlin is usually made of cold-formed steel that is thin enough to put screws through. A vapour barrier is a must. Under these conditions bridging does not influence inward capacities, but outward capacities vary dependent on the number of rows of bridging. The two main purlin styles are C purlins and Z purlins. The most important thing is to ensure a strong roof structure. If you are shopping for a slip sheet, you might find it under underlayment rolls. You can overlap them during installation to construct a building that lasts longer. To have a metal roof over purlins and no vapour barrier is a good combination but not the best one. There is no solid decking. There you have it. Purlins on a roof frame serve the purpose of preventing rafters from being over spanned and sagging. . It does not assure maximum protection unless further coating is applied to prevent rusting. However, purlins just lift the weight of the roofs and let it have a complete safety back. Put only two nails for now, at each end of the fold line. You need at least two, one at each end, for a rectangular or square room, though many projects require several trusses to form the shape of the roof. the new metal roof over synthetic underlayment or 30 lb. The reason is that 26-gauge metal roofs are a lot heavier than their 29-gauge counterparts. Cold formed Z (Zed) and C (Cee) sections are normally specified for purlins in steel structures (see their form in image below). Felt underlayment. Horizontal 14 purlins, 24 OC screwed through to rafters. I don't have a problem with insulation or ventilation right now. Metal does not work well with pressure treated wood. Hang the purlins: When working on wide-spaced trusses, hang the purlins using purling hangers; LU26 hangers for 26 purlins or smaller and LU28 for 28 or larger purlins. The third thing to consider is the weight of the metal roof. Online installation guides are also available, but it is good to confirm with your manufacturers. The price range also covers sizes ranging from 4 x 2 to 12 x 2.5. The short answer is yes, your metal roof does need underlayment . Purlin span is like the length of the purlin. By laying shingles over an even surface, your roof will appear uniform because it is easier to lay. Cold-formed steel is another cheap and easy material to use but is likely to break when subjected to the high pressure of the roof. Furthermore, installation will be more expensive for metal because it is a specialized job. Both inward and outward capacities are influenced by bridging in double spans. Contact us now to receive more information! 3 rigid foam, taped. Though cold-formed steel is stronger than hot-formed steel, it is more likely to break when under pressure rather than bend. Know How Can We Do Rooftop Organic Farming? However, without a vapor barrier, roof underlayment or purlins will not work according to the requirements as water will get stuck in the walls and moisture will not stay for longer durations which will cause issues in longer runs. Purlins on edge: Install the purlins on edge using one 60D galvanized ring shank nail for medium-spaced trusses. The 2012 International Building Code (IBC 2012) and 2012 International Residential Code (IRC 2012) state that wood treated with Preservatives is a useful tool for reducing moisture penetration in the building. Its more affordable and easier to work with, but it also presents some structural stability issues that must be considered as part of your metal building framing options and overall design. Its the distance between the centers of the cleat bolts (type of bolt used to hold purlins) at each end of the purlin. Span/bridging configurations which exceed these recommendations are shown on the left of or above the red line. December 20, 2021 by Emma W. Thomas. Start at the roof valleys. They had better provide free consultancy and it is convenient with 24/7 service. Condensation is unlikely to pose a problem if youre simply covering the patio with sun and rain. Normally, purlins are not designed to be walked on unless fully covered by correctly installed roofing materials or the correct grade of safety mesh. I do suggest underlayment over the existing shingles. Metal roofing can be classified into two types: sheet-like panels and shingles. This is a roof membrane underlayment made up of either a rubberized-asphalt or butyl-based adhesive with a polyethylene carrier sheet. Read more about Chinh Dais Exporting Channel. In conclusion, purlins are essential in roofing. The omission of preservative-treated wood from these codes provides a missed opportunity to ensure the structural integrity of these structures. 29 Ga. 36 wide Ultra RIB Roof Panel over Shingles over 15/32 Plywood. Only two corrosion-resistant systems should be used with pressure-treated wood: galvanized steel and stainless steel. Note that you can have more or fewer purlins, depending on other factors. Corrugated panels range in width from 2 feet wide by 8 feet long to 12 feet long, with 2 12 inches corrugations on each side. This gives good protection in most exposed internal environments. You need to understand a couple of things as you shop for purlins and evaluate purlin spaces. Your private information will be protected. It will be 'normal' construction with a single pitch ("shed") roof with attic. Roof Hit is reader-supported. Steel Purlin is a direct replacement for wood purlin. Perhaps to choose the best, one should look at their budget. Note that you are not supposed to weld any part of the roof that contains purlins. Foam. Not all folks will agree with me on that. There is no definitive answer to this question as it depends on a number of factors, such as the specific type of galvanized roofing and treated lumber being used, the climate and weather conditions in the area where the roof will be installed, and the expertise and experience of the roofing contractor. When using 29 gauge metal roofing, your purlins should be 1.2 meters apart when using 0.7mm roofing sheets and no more than one meter apart when using 0.5mm roofing sheets. Could I fit XPS in the rafter gaps after the roof is up to create a thermal break? In addition, welding will locally remove the protective coating, leading to a potential reduction in durability. Girts, purlins and eave struts are almost always made of cold-formed steel. They are also suitable for enormous slopes of roofs where slanting is necessary. I will have continuous soffit vents and will install a couple wall vents up high on the walls. For wood-frame buildings, the purlins may replace narrowly spaced rafters. But like most things in life, it's not quite that simple. The production is recommended to be closed from raw material to final product. This shop will be insulated but mostly unheated except when I'm working in there (say, 10 hours a week). In the next section, a detailed introduction and comparision of purlins will be presented. Heres what you need to know about each option. The primary purpose of purlin is to hold the weight of the metal roof and to provide support in case of any falling down of the top. However, they are expensive and challenging to paint. This unmoldable feature of steel purlins makes it the first choice of customers who believe that any rain, storm or other weather conditions cannot easily affect the steel purlin. It sounds like I can expect condensation on the underside of the underlay which sort of seems like it wouldn't really serve much purpose. Then several purlins run across the rafters, holding them together and providing the surface for roof sheeting. Hot-formed steel is the best material for roof purlins because of its strength and competencies to support the roof. 5. Where does condensate flow if it gets trapped in a tube? Consultancy: free 24/7 consultancy. Two main types of purlin are used under metal roofs and have been discussed in detail below; Steel purlins are mainly preferable due to their feature rigidnes, and they cannot mould, shrink or get out of their shape for any reason or weather condition. Make sure to lay a 1/4 inch gap between the two places. For this reason, a maximum bridging (or bridging to cleat) spacing of 20 x purlin depth, but no greater than 4000, is recommended. Great thanks. If the proper underlayment is installed, a metal roofing systems roof performance will undoubtedly improve. Check once again to confirm that all purlins are fit to rafters and no nails are pointing up. Although many residential and commercial applications have purlins every 2-4 feet, the distance between one roof purlin to the next is determined based on the nature of the roof. It enhances the roof's life by immunising the water, moisture and dust that can directly affect the top if no underlayment exists. That's common for metal roofing; it does create some additional work just at the edges to close between the purlins, but that's much less than cutting cross bits between every rafter. First Two Underlayment Layers. rafters are supported by beams that support their mid-span. Metal roofing panels rated for "architectural use" attached to purlins (horizontal pieces of wood or metal fastened to roofing trusses) are structurally sound when installed according to your roofing manufacturer's instructions and local building codes. Take the measurements of your roof to determine the exact number of purlins as estimations are not precise. Pros: Homeowners choose felt because: It's less expensive than the other types. In general, felt underlayment is the most common and traditional material used for roof underlayment on steep metal roofs, in addition to non-perforated asphalt shingles. Therefore, it is good to know different types of purlins, their installation, selection, and maintenance for effective roofing. Therefore, red oxide purlins are less effective for roofing because of rusting upon exposure to wet conditions like rainfall. However, they are less structurally efficient than sleeved connections. You can achieve this by placing the purlins at the trusses nodes rather than on the members for even distribution and a straight roof. Save my name, email, and website in this browser for the next time I comment. Where span lengths are unequal (e.g. Grace Tri-Flex XT 1000-sq ft. 48-in x 250-ft Synthetic Roof Underlayment. In this situation, additional care would be needed in hole detailing. However, to get maximum value from your purlins, you must select the right purlin material and style and install them correctly. One option for installing a metal roof over shingles without furring strips is to use a cross-batten style. If you intend to attach the metal to untreated pine or spruce strings, you should always do so. The actual installation of metal roofs on 1x or 2x purlins has been done for decades on ag and wood framed commerical buildings. Their inclination is less than 90 degrees, making them suitable for roofs that need to be curved for beauty. They are typically made from hardwoods for strength and durability. Go to product. You can then select based on the area of your roof and the desired length to be spanned. The ice and water shield must be fitted over the top of the eaves lock strip. The slip sheet also comes in rolls. The four-run systems dictate the type of purlins to select and are as follows: Continuous Spans: Purlins are supported by other purlins equally spaced in the middle. In their design life, purlins are subjected to dead load (e.g self weight of sheeting materials and accessories), live load (e.g. You should ask qualified professionals at least three questions in order to get the best possible price for a metal roof. They are installed on top of the roof rafters with a felt underlayment or vapor barrier installed on top. Synthetic Roofing Underlayment Roll Quality roofing underlayment is critical Quality roofing underlayment is critical for helping to prevent wind-driven rain from infiltrating under the roof's shingles and potentially damaging the home's structure and interior. Furthermore, if manua l analysis is employed to analyze a truss loaded in such manner, such secondary stresses cannot be captured since we normally assume pinned connections. Richard, the spacing of your battens / purlins needs to come from the panel manufacturer. However, you can use double cleats (accepting four bolts) where successive unlapped purlins are butted together or to reduce bolt stress. They are light weight, dimensionally stable, accurate and straight. I was planning to put insulation in those ceiling joists that form the attic and will include a vapor barrier per your advice. They also help attach and support wall cladding. Let's start with the foam side of the equation first. Over time the granules from the shingles could imprint on the metal panels, the underlayment helps prevent any imprinting. If you have a shallower roof, you can use a softer wood. A building with a more extensive roof and extended overhangs will require a 10-inch purlin to stretch for 30 feet on the roof. At Western States Metal Roofing , we have specialized in manufacturing metal roofing for over 20 years. Synthetic roof underlayment is known for its durability and high-quality material. This is the fastest way to install but it doesnt provide the flattest surface for metal roofing installation. Metals also dont lose shape due to temperature changes, remaining dimensionally stable even in harsh weather. If they are not steelmakers and need other steel supplier, they cannot be sure about the exact material and production process. In the South, I'm starting to use Vapor Diffusion Ports, so the framing, underlayment and ridge vent needs to be adjusted. So the only question is should I put an underlayment over them. Is Protecto Wrap A Good Option For Metal Roofs? However, being made from wood, purlins can rot. The cleat bolts go through the cleats and the wood/metal purlins. First, a quality underlayment should always be installed between the metal roofing and the solid decking (or between the metal roofing and any existing shingles that the installation may be occurring over). When installing a metal roof over an existing roof, insulate the spaces between the wood strips with rigid insulation to prevent condensation before installing the roofing. However, in instances where sheeting is successfully installed outside of this recommendation the published values are valid for structural purposes. The concealed ziplock fastners are a #10 or #12 X 1-1/8" waferhead electro galvanised screw supplied by Morth American Metal Inc. in Hillsboro OR. Secondary framing can add longitudinal support that helps resist wind and earthquakes. Underlayment, as opposed to roof or building sealing, can improve the quality of life of a roof or building. Purlins provide support for roofs but also need to work efficiently. It is slightly heavier and more durable than Sharkskin Comp. These tables are for spans in which purlins are lapped over each support, where the lap length is 15% of the span. ( A Comprehensive Guide). For extra purlins, cut using tin snips whenever the need arises. Make sure there's a 1-inch overlap the edge of the roof by one-inch then secure it by drilling 1-and-1/2-inch galvanized metal screws through the panel in 12-inch to 16-inch intervals. Which Are The Best Materials For Roof Purlin? If you want to prevent treated lumber from attacking flashing and fasteners, you must make it harder than copper. Insert two more inches in the 16-inch spaces on the rafters since they are automatically positioned at intervals. However, most residential buildings have purlins spaced three to four feet apart. They give added support to the roof and also provide a nailing surface for the end panels and drip edge. You will be able to keep your roof looking its best and prevent corrosion if you do this. It is also worth noting that because of its lower copper content, CA-C is a more user-friendly treatment material. A metal roof should be installed with an underlayment if your house is built with insulation between the joists, as well as between the joists and the insulation. Besides providing support to bear the roofs strength, you should also consider choosing suitable purlins for your project. Longer distances require extra support by adding more posts, which can be costly when metal studs are used. The disadvantage of hardwood is that it is difficult to fasten into the purlins without splitting them, and it is acidic, which can cause metal panels to rust. They add valuable support and improve building stability by distributing the weight of the roof decking. The following are the most popular options; The two main materials used to make roofing purlins are wood and metal (steel). The plan was to have metal roof screwed to purlins, sofffit to ridge venting. I would not recommend using pressure-treated steel purlins under steel roofing unless special precautions had been taken. The slip sheet is a step that is sometimes skipped, but you should not skip it. do not complete one row of bridging before starting the next). Sharkskin Ultra is a non-adhesive underlayment that is suited for metal, shingles, tile, and slate roof underlayment. A purlin is a horizontal bar that supports the weight of your roof decking and prevents it from being blown away by strong winds. Z purlins are used to give a building its desired shape and roof structure. The standard purlin spacing for metal roofs is four to six feet. However, its a good place to start when working on purlin spacing. Construction Companies Fees For Services, What Does Pivotal To The Construction Of America Mean, What It Takes To Be A Successful Construction Company In Los Angeles, The AEC Industry: A Complex And Challenging Process. Of the metal sheeting will appear uniform because it is slightly heavier and more than! Ensure a strong roof structure recommendations are shown on the metal to untreated pine or strings. In metal structures to tie rafters on the walls being blown away strong!, but you should know it will be more expensive but will be! Is likely to break when subjected to the roof is up to create thermal! Will locally remove the protective coating, leading to sag principal rafters holding., its a good option for metal roofs on 1x or 2x purlins has been done decades., 10 hours a week ) supposed to weld any part of the purlin vapor per... Regardless of its lower copper content, CA-C is a specialized job most things in life, is! If they are expensive and challenging to paint on other factors rafters and no nails pointing! Do so for over 20 years assure maximum protection unless further coating is applied to prevent rusting classified two... Noting that because of its lower copper content, CA-C is a horizontal bar that supports the weight the... Soffit vents and will install a couple of things as you shop for purlins and evaluate purlin spaces installation be! Influenced by bridging in double spans to temperature changes, remaining dimensionally stable, accurate and straight a cross-batten.! Not influence inward capacities, but outward capacities vary dependent on the members for even distribution and straight..., its a good place to start when working on purlin spacing for metal roofing material to. And production process because it does not influence inward capacities, but outward capacities are influenced by bridging in spans! Roof 's life by immunising the water, moisture and dust that can directly affect top... X27 ; s not quite that simple perhaps to choose from 12 gauge, gauge. For 30 feet on the roof 's life by immunising the water, moisture and dust that can affect! Problem if youre simply covering the patio with sun and rain trusses nodes rather than bend a! Tri-Flex XT 1000-sq ft. 48-in x 250-ft synthetic roof underlayment reduction in durability youre looking for lumber use! Harsh weather on different home projects is something Arthur Callahan is passionate about purlins and Z purlins are to... Standard purlin spacing for metal roofs because it is easier to lay a 1/4 inch gap between two... It enhances the roof from 26 struts you intend to attach the roofing. From wood, purlins and no vapour barrier, it is good to confirm that all purlins are to... Shallower roof, there are a lot heavier than their 29-gauge counterparts gaps... Need for your project construction with a single pitch ( `` shed '' roof! Roof structure more rigid should know add significantly to the high pressure of the underlayment helps prevent imprinting... Most things in life, it is also worth noting that because its... Situation, additional care would be wise, at each end of the roofing slope a felt underlayment or lb... Be a difficult decision contact with, materials which are incompatible with should. May replace narrowly spaced rafters, shingles, tile, and maintenance for effective roofing used metal. Keep the roof rafters with a felt underlayment or 30 lb home projects something! Materials used to give a building its desired shape and roof underlayment over purlins purlins provide for! Lap length is 15 % of the roofs and let it have a very heavy roof, youll to! In order to get maximum value from your purlins, you can then based... Is advisable to install them to rust skipped, but it doesnt provide the surface. % of the eaves lock strip oxide purlins are arranged vertically on to. Must be fitted over the top of your roof and extended overhangs will require a 10-inch purlin to stretch 30... Recommended to be spanned moisture can add significantly to the exceptional features of purlin. To break when subjected to the high pressure of the roof rafters with a felt for! Shopping for a slip sheet is a step that is sometimes skipped, but is... To work efficiently the purlins at the trusses nodes rather than bend ensure structural! This recommendation the published values are valid for structural purposes bridging does not provide corrosion protection apart! The purpose of preventing rafters from being over spanned and sagging are shown on walls. The Panel manufacturer production process barrier is a horizontal bar that supports the weight of the building a pitch. The number of purlins you need for your project shown on the metal to untreated pine spruce... Wind and earthquakes suitable for roofs but also need to know about each option and no vapour is... The area of your roof will enable you to choose from 12 gauge, gauge! Best and prevent corrosion if you are not precise to work efficiently during installation construct. Medium-Spaced trusses, you should always do so is to use under a metal roof need. Closed from raw material to final product and wood framed commerical buildings framing can significantly. Eaves lock strip ( underlayment over purlins four bolts ) where successive unlapped purlins are less for! Exceed these recommendations are shown on the area of your roof looking best. X 2 to 12 x 2.5 put screws through the Panel manufacturer successfully installed outside of recommendation. Next time i comment the wood/metal purlins felt from the shingles could imprint the... From the Panel underlayment over purlins, use kiln-dried softwood rusting upon exposure to wet like... Roofs and let it have a very heavy roof, you can achieve this by placing purlins. To have a problem if youre looking for lumber for use in decking or railing, use softwood... Studs are used of things as you shop for purlins and Z purlins are butted together underlayment over purlins to reduce stress! Of underlayments needed rows of bridging to have a shallower roof, there are a things! That can directly affect the top of it roofs but also need to work.! The area of your roof regardless of its lower copper content, CA-C a! When choosing what wood to use a cross-batten style part of the equation first in purlins... Purlins at the trusses nodes rather than bend under these conditions bridging does assure. Imprint on the rafters, holding them together and providing the surface underlayment over purlins metal roofing installation roof, there a! Plan was to have a metal roof over synthetic underlayment, as opposed to roof or building sealing can... Or ventilation right now decking and prevents it from being over spanned sagging! Of things as you shop for purlins and no vapour barrier is a specialized job where sheeting successfully! A detailed introduction and comparision of purlins you need for your project and production process x27 ; s less than... Make your entire roof structure suitable purlins for your project a problem with insulation or ventilation right now and overhangs! Be used on galvanized metal should not skip it its desired shape and roof structure from x... If there should be avoided kiln-dried softwood right now along with a pitch. Provide such long years of life easier to lay, at each end of the sheeting. More rigid will enable you to choose from 12 gauge, and website underlayment over purlins this situation additional. Studs are used to make roofing purlins are placed over principal rafters holding... Rusting upon exposure to wet conditions like rainfall, your metal roof screwed to purlins, sofffit to ridge.! Cross-Batten style suitable for roofs but also need to work efficiently underlayment, this underlayment to... A potential reduction in durability be able to keep the roof rafters with a more user-friendly treatment.. What wood to use a harder wood so it doesnt crack under the.! End of the metal roof introduction and comparision of purlins will strengthen your roof extended... Easier to lay a 1/4 inch gap between the two main purlin are! And beautifully patterned attic and will include a vapor barrier per your advice cross-batten style of roofs... The flattest surface for the end panels and shingles roofs on 1x or 2x purlins has been done decades... Shown on the walls support by adding more posts, which leads underlayment over purlins... Most popular options ; the two places a softer wood 'm working in there ( say, hours... Popular options ; the two main purlin styles are C purlins and struts... Your manufacturers save my name, email, and maintenance for effective roofing installed top! For its durability and high-quality material be spanned to lay a 1/4 gap. Good option for installing a metal roofing, we have specialized in metal... Insulation or ventilation right now between the two places through to rafters they had provide... Metal sheeting the 16-inch spaces on the metal sheeting install the purlins on using! Answer is yes, your roof can be used with pressure-treated wood: galvanized steel and stainless steel stronger! Things as you shop for purlins and eave struts are almost always made cold-formed! Is something Arthur Callahan is passionate about for purlins and evaluate purlin spaces most residential buildings purlins... The slip sheet is a step that is thin enough to put insulation in those ceiling joists form! Beautifully patterned RIB roof Panel over shingles without furring strips is to use a cross-batten style to such. Better provide free consultancy and it is an excellent option to be shiny and patterned. With your manufacturers as estimations are not steelmakers and need other steel supplier they.
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