Calculation of drainage by roof area

Any building’s roofing system must be able to calculate drainage by roof area in order to remain efficient and intact. In addition to preventing water damage, proper drainage increases the roof’s lifespan. Understanding the fundamentals of roof drainage calculation will assist you in making wise decisions and guaranteeing that water is properly drained off your roof, whether you’re a builder, architect, or homeowner.

Finding the area of the roof is the first step in calculating roof drainage. Depending on the standard units used in your area, this is usually measured in square feet or square meters. The area of your roof encompasses all of the slopes and angles of the roof surface, not just the measurements measured from the ground. Calculating the total area of a complex roof, like one with several peaks or valleys, can be more precise if the roof is divided into sections and each is calculated independently.

The local rainfall intensity is the next factor to take into account after determining the total roof area. The amount of rain that falls each hour is typically measured in inches or millimeters and varies depending on the region. This information is important because it helps calculate the amount of water your roof will require in order to properly drain during a storm. Guidelines regarding minimum rainfall intensities to take into account for drainage calculations are frequently provided by local building codes or standards.

Finding the necessary drainage capacity is the next step, once the roof area and rainfall intensity are known. This capacity, which is commonly expressed in liters per second (L/s) or gallons per minute (GPM), indicates the greatest volume of water that must be removed from the roof surface in a predetermined amount of time, usually during periods of high rainfall. It’s critical to take into consideration elements that could affect water flow, such as roof slope, material, and obstructions like chimneys or skylights.

The last step in guaranteeing efficient roof drainage is selecting the appropriate drainage system. Choosing gutters, downspouts, and drainage pipes that can manage the estimated drainage capacity without overflowing or clogging is the decision at hand. The size and composition of the drainage components, as well as their upkeep needs and longevity, are important considerations. The drainage system must be installed correctly and inspected frequently to guarantee that it keeps working at its best over time.

Roof Area (square feet)	Required Drainage (inches per hour)
1000	5
1500	7
2000	9

The optimal number of funnels

The main purpose of the internal system of the drainage system is to ensure the removal of water from the roof at any air temperature on the street and regardless of the amount of precipitation. Water disposal is recommended to be carried out in a general or rain sewer. The calculation of the number of funnels of the internal drainage is carried out according to the rule: 1 funnel by 0.75 m 2 roofs and 1cm 2 pipes for water drainage. The funnels of the internal system are located along the longitudinal axis of the roof. It is forbidden to equip funnels and risers in the thickness of the external walls, due to their possible freezing in the winter period.

The following criteria are taken into consideration when calculating the number of gutters:

• If there are no obstacles to the linear expansion of the gutter up to 12 meters long, then one funnel will be enough;
• with a gutter length of more than 12 meters and there are obstacles to expand it, then one special compensating funnel will be required at the end of the slope;
• If the groove is encircling the building around the perimeter, then a joint installation of funnels and compensators will be required.

Their passport data, which includes details on geometric sizes, fastening techniques, and throughput, must be used to calculate the drainage funnels. The total number of drain pipes in the drainage system should match the number of gutters.

Features of calculating gutters and pipes

The entire building should be thoroughly inspected for the presence of architectural features, protruding parts, and hollows before setting up an external drainage system. If the drainage system does not fit harmoniously on the facade, it should be hidden from view. The drainage system should not detract from the building’s external appearance. Many accessories are used for these purposes, and they are mass produced nowadays.

The area of the roof that will be used to remove water must always be measured before calculating the drainage system. With only the most basic geometric formulas known, this can be easily accomplished. It can be agreed upon that a 100 mm water drain pipe can, in theory, function efficiently on roof areas up to 220 m 2.

The calculation of the cross section of the drainage gutter is performed taking into account the angle of the roof slope, the cooler it is, the higher the height of the gutter should be higher. This is primarily due to an increase in the area of ​​rainfall, which are the main source of water. The number of gutters is selected based on the perimeter of the cornice and components offered on the market. So, most plastic gutters have a length of 3 or 4 meters, and galvanized – 2 meters. If the length of the cornice is 10 meters, then we will need 5 galvanized grooves or 2 pieces of 4 meters and one by 3 meters in the case of plastic parts.

It’s crucial to understand that there are always one more connecting coupling for every gutter than there are gutters.

The following formula is used to determine the quantity of fasteners needed:

Where the number of hooks, n, is;

L is the cornice’s length;

0.6 is the recommended distance between hooks as stated in regulatory documents.

The following formula can be used to determine how many drain pipes there are:

Where n denotes the quantity of drain pipes;

Ncornice: the elevation between the ground and the cornice;

Nbending refers to the pipe’s bend height;

Inserts: the length of the funnel’s insert;

Drain pipe length, measured in meters (usually 3 or 4).

It’s crucial to understand that every drain pipe segment should be attached using a minimum of two clamps.

The maximum amount of water that can come from the roof must be determined in order to calculate the internal drain on the pipe’s cross section. In order to calculate the maximum amount of precipitation for a particular area, the roof’s geometric parameters—length and width—are measured. Generally, a simplified formula is applied, keeping in mind that 1 cm 2 of the drain pipe corresponds to approximately 1 m 2 of the roof.

SNiP controls how the drainage system is calculated while accounting for the impact of numerous variables, such as:

• the number of atmospheric precipitation per year;
• climatic zone and maximum negative temperature;
• roof area;
• the presence of rain sewage;
• Other factors.

If you calculate the roof’s gutters well in advance, you can minimize the amount of drainage system parts you need to buy and save a lot of money.

Similar news

How to calculate gutters for a roof

The installation of protective materials and the atmospheric water drainage system are both components of a properly arranged roof. The drains must be correctly calculated in order to finish this task. You have two options: do the required computations on your own or hire specialized engineering firms.

Elements of the drainage system ↑

To begin with, you must ascertain which components belong in the water-pounding roof binding. The following elements ought to be part of the most basic plan.

1. GOLOBE. Designed to collect precipitation flowing from the surface of the roof.
2. Funnel. Installed in the gutter and serves to remove moisture from its capacity.
3. Pipe. It is attached vertically and necessary for further transportation of water to the processing or storage system.
4. Additional elements – fasteners, angular turns of gutters, plugs, tees, pipes of pipes T.D.

You must first examine the roof’s layout in order to determine the gutter requirements. You can create a closed (encircling) drain or one made up of separate parts depending on this.

This is determined by the roof’s shape; two gutters are installed, not connected, on standard gable structures. According to Valmova, a closed channel system must be installed.

The material used to manufacture the elements is also significant. Traditionally, goods made of zinc were used. However, plastic models have become very popular recently.

Galvanized ↑

Resistance to temperature variations and minimum temperature expansion are the key benefits. Nonetheless, their primary drawback, shared by all metal materials, is their vulnerability to rusting. A layer of pool or plastisol covers modern models for protection. The components’ life is extended in this way.

Plastic ↑

Distinguished by a light weight and a cozy groove technique with extra adhesive strapping. Low mechanical strength and a high coefficient of linear temperature expansion are the drawbacks.

The calculated part ↑

What should I take into account when designing drainage schemes correctly? The roof’s overall area should be considered first. Installing one groove is possible if this parameter is less than or equal to 100 m². Simultaneously, however, the roof gutters must be calculated using the fact that 1.5 mm³ of pipe working section should be supplied for every 1 m² of coating.

Examine the primary phases involved in putting geometric computations and drainage’s quantitative parameters into practice.

Only when the slope angle is at least 12 ° is it feasible to install a drainage system cornice. In the event that this requirement is not met, drainage under the roof must be installed. Its layout is comparable to that of a flat coating, which is what we’ll talk about next.

Diameter and length of the grooves ↑

Directly depends on the Skut Square. This component ought to guarantee the gathering of precipitation and its conveyance to gutters intended for receiving it. Oval structures with the standard sections 75, 80, 87, 100, 120, and 150 mm are most often used.

Therefore, it is advised to use DIN 18460-1989’s guidelines when calculating the gutters for a roof with less bandwidth. This document states that the diameter of the vertical pipe and the transverse cut of the gutter are dependent on the area of the roof.

• DIN EN 612-2005 “Groove gutter and gutters with a welded seam of metal sheets. Definitions, classification and requirements "
• DIN EN 1462-1997 "Holders of suspended gutters. Requirements and tests "
• DIN EN 607-2005 “GOLOBAR DEMPENSION and Fittings made of non-plasticized polyvinyl chloride. Definitions, requirements and tests ".

Area of the roof, in meters

L/s for system capacity

Diameter of the pipe, in millimeters

The gutters’ total length is the same as the slope’s exterior. Nonetheless, creating a prefabricated structure out of multiple models is required in the great majority of situations. Connecting elements (n Sood), the number of which depends on the number of components (n yellow), are required for practical implementation. This formula is used to calculate them.

N Zhel – 1 = N Soid

It’s also crucial to keep in mind that the ends of the structures won’t line up with one another when they are installed. The drainage system that is chosen will determine the installation distance, which can range from 3 to 8 mm.

Vorona parameters ↑

There are no established guidelines for the maximum number of funnels. Their number makes sense in relation to a comparable vertical pipe indicator. There is a maximum, though, of 24 meters that should separate funnels.

The working portion of the gutter and the water intake channel’s diameter must match. Otherwise, water will build up in the horizontal elements of the system when it is fully loaded.

The number of fasteners ↑

Special fasteners are used to install components on the cornice. The length of the drainage canals and the materials used to make the pipes determine their number and arrangement.

The fastener is intended for installation on either a roof crate or a cornice board, depending on the configuration. Nevertheless, the following formula can be used to accurately calculate the external drainage of the number of fasteners.

• Where l is the length of the cornice;
• 0.6 – optimal distance between fasteners.

This formula only applies to systems that are external. When making calculations for a flat roof, the area of the cornice is more important than its length.

Distribution pipes ↑

Using the grooves, the drain pipes’ diameter was computed. Accurately determining the length of the vertical drain’s direct section is far more crucial. The size of the upper knee and the tip at the bottom must be considered in order to accomplish this. It is inappropriate to use a general formula for this because installation tolerances vary amongst schemes. As such, it is advised that you become acquainted with the manufacturer’s recommendations. It is crucial that there be no more than 300 mm separating the tip and the water intake.

How can I determine the drain based on the quantity of pipes? For every 70 m² of roof, one vertical pipeline is needed on average. In this instance, the diameter should be chosen based on the data that is shown in the gutter calculation section.

Furthermore, you must be aware of the ideal quantity of clamps to use when fastening the pipe to the building’s facade. One fastener should be installed every three meters of drain. However, you also need to consider the wall’s architectural features, as mounting bypass knees is frequently required. In addition, this section of the pipeline needs to be fixed with a minimum of two clamps.

Almost any drainage can be calculated using this scheme. Even before they are installed, the dimensions of each component should be considered. This calls for a preliminary installation plan, which will enable you to purchase the ideal quantity of necessary components in addition to assisting with a professional installation.

Flat roof ↑

Drainage systems must also be installed for this kind of roof. The issue is that component installation needs to happen while the roof is being arranged.

The simplest method of calculating the internal drain just considers the roof’s overall area. You need one funnel for every 0.75 m². The internal horizontal pipes should have a minimum slope of 15 degrees. Generally speaking, only large residential and commercial buildings are outfitted with such a system. Due to its considerably inferior qualities compared to a pitched roof, flat roof structures are extremely uncommon in private homes.

It is best to use specialized software systems for gutter calculations. As a result, it is feasible to reduce the likelihood of error and create the ideal drainage system arrangement.

Calculation of the drainage system

As the company’s director, my name is Mikhail, and I have over 15 years of experience working only with roofs. I’ll explain the nuances and trade secrets of the roof’s materials below. Will be pleased to assist and respond to inquiries. LLC Mikhail "STM-Stroy"

No home could be complete without drains since excessive damage could result in water just pouring off the overhang. The drainage system is calculated in order to arrange spills competently and effectively.

Maintaining the integrity and efficiency of any building’s roofing system requires knowing how to compute drainage requirements based on roof area. Proper drainage and prevention of water damage can be achieved by property owners by accurately estimating the amount of rainwater that needs to be managed.

First, the roof’s footprint must be measured in order to calculate the roof area. Usually, this can be accomplished by multiplying the building’s length and width. Accurate measurements are ensured for complex roof shapes by breaking the roof into manageable sections and computing each one separately.

Next, take into account the local rainfall intensity, which differs depending on the region. The amount of water that the roof must manage during intense downpours is directly impacted by this factor. One can estimate the amount of water that requires effective drainage systems by comparing the computed roof area with the data on local rainfall.

It’s also essential to comprehend the materials that were used to build the roof. The way that different materials absorb and release water affects the drainage needs. For example, due to their different surface qualities and water runoff characteristics, metal roofs may require different drainage considerations than tiled or shingled roofs.

Finally, it’s critical to select suitable drainage systems, including drains, downspouts, and gutters. For these systems to effectively divert rainfall away from the building’s foundation and avoid structural problems and possible flooding, they must be properly sized and positioned.

"Estimating roof drainage is essential for efficient water management and building upkeep. It is possible to ensure that drainage systems can effectively handle rainwater, preventing potential damage and maintaining structural integrity, by accurately measuring the area of the roof and performing basic calculations. This article examines easy ways to calculate roof area, variables that affect drainage needs, and useful advice for professionals and homeowners on how to maximize water flow and safeguard their roofs."

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