An Overview of How to Drain Water from Built-up Roofs?

Built-up Roofs:

Built-up roofs (BURs) are popular for commercial and industrial buildings due to their durability and weather resistance. However, they can be susceptible to water pooling, which can cause structural damage, leaks, and reduced lifespan. Proper drainage is essential to maintaining the integrity of a built-up roof. This guide outlines the steps and strategies for effectively draining water from built-up roofs.

Understanding Water Drainage Issues in Built-up Roofs

Before implementing drainage solutions, it's important to understand the common causes of water accumulation on built-up roofs:

Poor Roof Slope:

Built-up roofs are typically low-sloped or flat, making them more prone to standing water.

Clogged Drainage Systems:

Debris, leaves, and dirt can block drains, gutters, and scuppers.

Improper Installation:

Incorrectly designed drainage systems can lead to inadequate water flow.

Structural Settling:

Over time, buildings settle, causing depressions where water can collect.

Methods to Drain Water from Built-up Roofs

There are several methods to ensure efficient water drainage from built-up roofs:

Installing Proper Drainage Systems

Internal Drains

·         Internal drains are strategically placed on the roof to collect water and direct it through pipes inside the building.

·         To prevent clogging, regularly inspect and clean these drains.

Scuppers

·         Scuppers are openings in the roof’s perimeter that allow water to drain into downspouts.

·         To ensure optimal drainage, ensure scuppers are clear of obstructions.

Gutters and Downspouts

·         Install gutters along the roof edges to channel water away.

·         Regularly check for blockages and perform routine maintenance.

Adjusting Roof Slope and Adding Tapered Insulation

·         A minimal slope (at least 1/4 inch per foot) helps water move towards drains.

·         Tapered insulation can be installed to direct water towards drainage points.

Installing a Roof Cricket

·         A cricket is a raised structure that diverts water from obstacles like HVAC units and chimneys.

·         It prevents water pooling in critical areas.

Maintenance and Prevention of Water Accumulation

Regular Inspections

·         Conduct inspections after heavy rainfalls to check for pooling.

·         Address any low spots or drainage issues immediately.

Cleaning and Debris Removal

·         Remove leaves, dirt, and debris from drains and gutters regularly.

·         Schedule professional cleanings if necessary.

Roof Repairs and Resurfacing

·         Repair cracks or damaged areas that might contribute to water pooling.

·         Apply coatings or waterproof membranes for additional protection.

Using Siphonic Drainage Systems

·         Siphonic systems enhance water flow through drains using air pressure differences.

·         These systems are effective for large commercial roofs.

Emergency Water Removal Techniques

In case of severe water accumulation, emergency removal methods may be necessary:

·         Using a Squeegee or Broom to push water towards drains manually.

·         Pumping Water Out with a sump pump or wet vacuum.

·         Hiring Professionals if drainage problems persist or pose a risk to the building.

Different Types of Built-Up Roofs (BUR)

Built-up roofing (BUR) is one of the oldest and most reliable systems for low-slope and flat roofs. It comprises of several layers of bitumen and reinforcing fabrics, making a hard-wearing and weather-resistant surface. Different variations of BUR systems exist based on the materials and application method. Below are the main types:

Hot Built-Up Roof (Hot BUR)

Hot BUR is the most traditional type and is constructed using asphalt or coal tar layers applied in a heated, liquid form. These layers are reinforced with fiberglass or organic felt sheets, creating a waterproof barrier. The top layer is usually finished with gravel or a reflective coating to enhance durability and UV protection.

Pros:

·         Highly durable and long-lasting

·         Excellent waterproofing capabilities

·         Strong resistance to foot traffic

Cold Built-Up Roof (Cold BUR)

Unlike hot BUR, cold BUR uses cold-applied adhesives or modified bitumen instead of heated asphalt. These adhesives are solvent- or water-based, making them safer and easier to apply.

Pros:

·         Safer application with no need for hot asphalt

·         Lower installation costs

·         Condensed environmental impact due to rarer emissions

Ballasted Built-Up Roof

A ballasted BUR system, like traditional BUR, consists of multiple layers of bitumen and reinforcing fabric. However, instead of gravel embedded in asphalt, large stones or pavers are used to hold the roofing system in place.

Pros:

·         Quick installation process

·         Cost-effective compared to fully adhered systems

Modified Bitumen Built-Up Roof

Modified bitumen BUR is an improved version of traditional BUR. It incorporates polymer-modified bitumen sheets that offer enhanced flexibility and strength. These sheets can be torch-applied, cold-applied, or self-adhered.

Pros:

·         Greater resistance to temperature fluctuations

·         Easier installation compared to traditional BUR

·         Improved flexibility reduces cracking

Conclusion:

Proper drainage is critical for maintaining the longevity and performance of built-up roofs. These strategies can protect your roof from water damage and enhance its lifespan. Built-up roofing is popular for commercial and industrial buildings due to its durability and weather resistance. Expert roofers in Croydon can help you choose the right type of BUR depending on factors like budget, climate, and structural load capacity.