Understanding the Construction of Parapet Walls
Table of Contents
What are Parapet Walls?
Parapet walls are vertical structures at the edge of a roof, terrace, balcony, walkway, or other elevated surface. They extend above the line of the roof and there are many types of parapet walls:
Safety: They act as barriers to prevent people from falling off the edge of a roof or elevated area.
Aesthetics: They can be designed in various styles to enhance the architectural appeal of a building.
Fire Protection: In historical and some modern contexts, parapet walls can act as a fire barrier, preventing or slowing the spread of fire from one building to another or across a roof.
Concealment: Parapets can hide rooftop equipment like air handlers, condensers, and other mechanical systems from view, maintaining the building’s aesthetic.
Weather Protection: They can protect the roof and side of the building from weather elements, such as wind, rain, and snow.
Structural Support: Parapet walls can provide support for rooftop features such as signage, railings, or greenery.
They have been used historically in fortifications, where they provided cover for defenders on the walls of castles or city ramparts. In modern architecture, they are used for both practical and decorative purposes. They can be constructed from various materials, including brick, stone, concrete, metal, or glass, and may feature different designs such as plain, embattled, perforated, or panelled.
8 Types of Parapet Walls
Parapet walls come in various types, which can be classified based on their appearance or shape and configuration. Here are the different types of walls based on appearance:
Based on Appearance
1.Plain Walls: These are simple vertical extensions of the wall at the edge of the roof, primarily provided for safety concerns. They are easy to construct and require low maintenance but are generally less aesthetically appealing.
2.Perforated Walls: These walls are similar to plain parapets but have openings or perforations of different sizes and shapes for aesthetic purposes. The perforations can be in various designs, such as circles, trefoils, or flower shapes.
3.Panelled Walls: Panelled parapets are similar to plain parapets but are ornamented with a series of panels, which may be oblong or square. These panels add depth and decoration to the wall without perforations.
4.Embattled Walls: Historically used in castles and forts, embattled parapets have alternating high and low sections, providing a notched appearance. They were used for defence in the past but now serve to enhance the aesthetic appeal of structures.
Based on Shape and Configuration
5.Flat Wall: Commonly used on flat roof structures, these parapet walls have little or no slope and are straightforward in design.
6.Sloped Wall: These are designed for sloped roof structures and are constructed to follow the slope of the roof.
7.Stepped Wall: Resembling a staircase, stepped parapet walls are used for inclined roof structures and add a distinctive architectural feature.
8.Curved Wall: Also known as arched parapet walls, these can be used on both flat and inclined rooftops and offer a unique visual appeal.
Miscellaneous Types
– Modern Walls: These include newer materials and designs, such as fiberglass parapets or parapets with steel railings. Composite parapet walls may combine materials like glass or steel with traditional parapet designs.
– Glass Walls: Utilizing glass, these parapets offer a modern look and can serve as windbreakers while providing unobstructed views.
Each type of parapet wall serves specific purposes, from safety and aesthetics to historical significance. The choice of parapet wall will depend on the architectural style of the building, the desired functionality, and the local building codes and regulations.
5 Step to Constructing Parapet Wall
Constructing a parapet wall involves several steps, from planning and design to the actual building process. Here’s a detailed guide on how to construct a parapet wall:
- Design and Planning
– Determine the Purpose: Decide on the primary function of the parapet wall (e.g., safety, aesthetics, fire protection).
– Choose the Type: Select the type of parapet wall you want to construct (e.g., plain, perforated, panelled, embattled) based on the architectural style and purpose.
– Design Considerations: Consider the height, thickness, and materials for the parapet wall. The design should comply with local building codes and regulations regarding minimum heights and structural requirements.
- Material Selection
-Choose Materials: Select materials that are durable and suitable for the local climate. Common materials include brick, concrete, stone, and metal.
– Coping Material: Decide on the material for the coping, which is the protective cap on top of the parapet wall. Options include stone, metal, or precast concrete.
- Construction Process
-Foundation Preparation: Ensure that the roof or the structure where the parapet wall will be built has a strong foundation to support the additional weight.
– Building the Wall:
– Erect a scaffold for easy access to the construction area.
– Start by laying the first course of bricks, blocks, or other chosen materials, ensuring they are level and properly aligned.
– Continue building the wall to the desired height, using mortar to bond the materials. Include weep holes for drainage if necessary.
– Installing Coping:
– Once the wall reaches the desired height, install the coping on top. The coping should overhang slightly on both sides to direct water away from the wall.
– Secure the coping with mortar or adhesive, depending on the material. Ensure it’s level and properly sealed to prevent water penetration.
- Waterproofing and Finishing
– Apply Waterproofing: To prevent moisture penetration, apply a waterproofing membrane or sealant on the wall and under the coping.
– Finishing Touches: Apply any desired finishes, such as paint or sealant, to protect the wall and enhance its appearance.
- Inspection and Maintenance
-Regular Inspection: After construction, regularly inspect the parapet wall and coping for any signs of damage or wear, such as cracks or loose materials.
– Maintenance: Perform necessary maintenance, such as resealing the coping or repairing damaged sections, to ensure the longevity of the parapet wall.
6 Reasons for parapet walls being damaged
Common causes of damage to parapet walls include:
Cracking and Crumbling: Fluctuations in temperature are a primary cause of cracks and mortar deterioration in parapet walls. Persistent freeze-thaw cycles result in the contraction and expansion of the masonry materials, leading to cracks, loosened bricks, and crumbling mortar.
Water Seepage: Water ingress through cracks, crevices, and gaps is another significant cause of parapet wall failure. When the inner roof membrane is exposed to water, it can cause bubbles, blisters, molds, mildew, and wood rot. Improper drainage and debris accumulation in gutters can lead to pooling, causing leaks.
Material Deterioration: Weathering and erosion due to aging are common phenomena that lead to peeling or fading paint, surface deterioration, and mortar disintegration.
Moisture Infiltration: Common building enclosure issues for neglected parapets include moisture infiltration, which can lead to corrosion, cracking, and spalling.
Expansion and Movement: Walls tend to expand outward from the center, with the greatest degree of movement towards their ends. Lack of provision for expansion and movement, such as not providing expansion joints at or near building corners, can lead to stress along the structure, observable as continuous step cracks or bowing and displacement.
Hail Damage: On flat roofs, hail damage to parapet walls can be severe, causing long-term damage that might be more costly to repair than replacing the whole roof.
These causes highlight the importance of regular maintenance and inspection to prevent and address damage to parapet walls effectively.
How to repair parapet wall
Repairing parapet walls involves several steps and techniques to address common issues such as moisture ingress, structural instability, and aesthetic deterioration. Here’s a comprehensive guide on how to repair parapet walls:
Initial Assessment
– Identify Problems: Conduct a thorough inspection to identify issues such as cracks, crumbling mortar, water seepage, or structural weaknesses.
Structural Repairs
– Reinforcement: If structural instability is a concern, consider adding more wall ties to increase lateral stability, or tie the parapet back to adjacent structures if possible.
– Masonry Repair: Replace damaged bricks or stones, and repoint the mortar joints where necessary. Use materials that match the existing masonry to maintain aesthetic consistency.
Moisture Control
-Coping Replacement: Remove and replace damaged coping stones or caps. Ensure that new copings are properly installed with an overhang to direct water away from the wall.
– Waterproofing Membranes: Apply waterproofing membranes or sealants to prevent water ingress. This is particularly important at the top of the parapet where the coping sits.
– Flashing and DPC Installation: Install or replace flashings and damp proof courses (DPC) to prevent water from penetrating the masonry.
Aesthetic Improvements
– Cleaning: Clean the parapet walls to remove dirt, stains, and biological growth. This can involve gentle washing or chemical treatments depending on the severity of the soiling.
– Rendering or Painting: Apply new render or paint if the original surface is extensively damaged or to improve the wall’s appearance.
Preventative Measures
– Regular Inspections: Schedule regular inspections to catch and address new issues before they become severe.
– Proper Drainage: Ensure that gutters and drainage systems are clear of debris to prevent water from pooling on or near the parapet.
Advanced Techniques
-Tuckpointing and Grinding: Use tuckpointing to restore mortar joints and grinding to smooth out uneven surfaces.
– Use of Modern Materials: Consider using modern, durable materials for repairs to enhance longevity and performance.
What is a Parapet Coping?
Parapet coping refers to the protective cap or cover placed on top of a parapet wall. Its primary function is to protect the wall’s top surface from water damage, weathering, ultraviolet light, and general exposure to the exterior environment. Parapet coping can be made from various materials, including metal, stone, concrete, and brick, each offering different aesthetic and functional benefits. The coping is designed to shed rainwater away from the wall surfaces beneath it, preventing water penetration that can lead to structural damage such as mold, damp, and rot.
The design of parapet coping often includes features such as a sloped top surface to facilitate water runoff and drips or throats on the underside to ensure that water drops clear of the wall surface below, rather than running down the face of the wall. Coping not only serves a practical purpose in preserving the structural integrity of the wall but can also be an aesthetic element, enhancing the building’s exterior appearance. It is a crucial component in building construction and renovation projects, requiring careful selection and installation to ensure effective water management and long-term durability.