Use of Rat Trap bond masonry in USA

 

Rat trap bond masonry is a construction technique that has been used for centuries in various parts of the world. It has become increasingly popular in recent years due to its cost-effectiveness, energy efficiency, and aesthetic appeal. While the use of rat trap bond masonry is not as widespread in the United States as in other countries, it is gaining momentum in some areas. In this article, we will discuss the use of rat trap bond masonry in the United States, including its advantages, disadvantages, and applications.

Advantages:

1. Improved insulation: Rat trap bond masonry provides better insulation than traditional construction methods. The interlocking pattern of the bricks creates an air gap that helps regulate temperature within the building. This can lead to lower energy costs and improved comfort for occupants.
2. Cost-effective: Rat trap bond masonry requires fewer bricks than traditional construction methods. This means that the cost of materials is reduced, as well as the time required for construction.
3. Structural strength: The interlocking pattern of the bricks provides added structural strength, making it a good choice for buildings in areas prone to seismic activity or extreme weather conditions.
4. Aesthetic appeal: The unique pattern created by the rat trap bond technique can be visually appealing and add character to a building.

Disadvantages:

1. Requires skilled labor: Rat trap bond masonry requires skilled labor for proper execution. This can lead to higher labor costs and longer construction times.
2. Limited availability: Rat trap bond masonry is not widely used in the United States, which can make it difficult to find experienced builders who are familiar with the technique.
3. Not suitable for all applications: Rat trap bond masonry is best suited for low-rise buildings with relatively low structural loads. It may not be suitable for large commercial or industrial projects.

Applications:

1. Residential construction: Rat trap bond masonry is a good choice for residential construction projects where cost-effectiveness, energy efficiency, and aesthetic appeal are important considerations.
2. Historic restoration: The technique can be used to restore the original appearance and structural integrity of historic buildings, while also providing improved insulation properties and greater structural strength.
3. Small commercial projects: Rat trap bond masonry may be used in small commercial projects, such as offices, retail spaces, and warehouses, where the weight and load-bearing requirements of the building are relatively low.

Conclusion:

Rat trap bond masonry is a construction technique that is gaining popularity in the United States due to its cost-effectiveness, energy efficiency, and aesthetic appeal. While it is not as widely used in the United States as in other countries, it has been successfully used in residential and small commercial projects, as well as in historic restoration. As more builders become familiar with the technique, we may see increased adoption of rat trap bond masonry in the United States in the coming years.

 

Scope of Rat Trap Bond Masonry in Canada

 

Introduction: 

Rat trap bond is a masonry technique that has been used in construction for centuries. The technique involves laying bricks in a specific pattern that creates a series of interconnected spaces within the wall, providing improved insulation properties and greater structural strength. Rat trap bond has been used in many parts of the world, including traditional Indian architecture and medieval Europe. In recent years, the technique has gained popularity in Canada, particularly in residential construction projects. This article will explore the scope of rat trap bond in Canada, including its advantages, disadvantages, and applications.

Advantages: 

There are several advantages to using rat trap bond in construction projects in Canada. Firstly, it is a cost-effective way to build walls that are thicker than normal. This is because the technique uses fewer bricks than traditional construction methods, as the spaces between the bricks are filled with mortar instead of solid brick. This reduces the cost of materials and labor, making rat trap bond an attractive option for builders on a tight budget.

Secondly, the technique provides better insulation properties than traditional construction methods. This is because the interconnected spaces within the wall create a natural air gap, which helps to regulate the temperature within the building. This is particularly important in Canada, where temperatures can fluctuate dramatically throughout the year. Improved insulation can help to reduce energy costs and make the building more comfortable for its occupants.

Finally, rat trap bond provides greater structural strength than traditional construction methods. This is because the interconnected spaces within the wall provide additional support to the structure, making it more resistant to lateral forces such as wind and earthquakes. This is particularly important in Canada, where some regions are prone to seismic activity.

Disadvantages: 

While there are many advantages to using rat trap bond in construction projects in Canada, there are also some disadvantages to consider. Firstly, the technique is more time-consuming than traditional construction methods, as each brick must be laid in a specific pattern. This can increase labor costs and extend the construction timeline, which may not be practical for some builders.

Secondly, the technique requires a high level of skill and expertise, as any errors in the laying of the bricks can result in structural weakness or instability. This means that builders must be trained in the proper use of the technique, which may not be feasible for all construction companies.

Finally, the technique is not suitable for all types of construction projects, as it is best suited to buildings with relatively low structural loads. This means that it may not be practical for large commercial or industrial projects, where the weight and load-bearing requirements of the building are significant.

Applications: 

Rat trap bond is a versatile construction technique that can be used in a variety of applications in Canada. It is particularly well-suited to residential construction projects, where cost-effectiveness and improved insulation are key priorities. Rat trap bond can be used to build exterior walls, interior walls, and even foundation walls in residential construction projects.

In addition, rat trap bond is sometimes used in commercial and industrial construction projects in Canada, particularly in smaller buildings with relatively low structural loads. This includes office buildings, retail spaces, and warehouses.

Finally, rat trap bond is sometimes used in historic restoration projects in Canada. The technique can be used to restore the original appearance and structural integrity of historic buildings, while also providing improved insulation properties and greater structural strength.

Conclusion: 

Rat trap bond is a cost-effective and practical construction technique that has gained popularity in Canada in recent years. The technique provides improved insulation properties and greater structural strength compared to traditional construction methods, making it an attractive option for builders in a variety of applications. While there are some disadvantages to using rat trap bond, including the need for a high level of skill and expertise and the limitations on its use in large commercial or industrial projects, the benefits of the technique make it a valuable tool in the construction industry in Canada.

 

History, Technique, Advantages, Disadvantages, Applications of Rat Trap Bond Masonry

 

Introduction: 

Rat trap bond is a masonry technique used in civil engineering for building walls that are thicker than normal. The technique is called "rat trap bond" because the shape of the bricks used in the wall creates a series of interconnected spaces that resemble a rat trap. This type of bond is often used in construction projects where the appearance of the wall is important, such as in residential homes, but it also has functional advantages, including better insulation and improved strength.

History: 

Rat trap bond is not a new technique; it has been used in construction for centuries. In fact, it was commonly used in traditional Indian architecture and is still used today in many parts of the country. The technique was also used in medieval Europe and is still used in some parts of Europe today. The main reason for its popularity is the fact that it is a cost-effective way to build walls that are thicker than normal.

Technique: 

The rat trap bond technique involves laying bricks in a particular pattern that creates a series of interconnected spaces within the wall. The bricks are laid with their ends facing outwards, rather than their long sides, which creates the distinctive "rat trap" shape. The spaces between the bricks are then filled with mortar, which provides stability and strength to the wall. The end result is a wall that is thicker than normal, with improved insulation properties and greater structural strength.

Advantages: 

There are several advantages to using rat trap bond in civil engineering. Firstly, it is a cost-effective way to build walls that are thicker than normal. This is because the technique uses fewer bricks than traditional construction methods, as the spaces between the bricks are filled with mortar instead of solid brick. Secondly, the technique provides better insulation properties than traditional construction methods. This is because the interconnected spaces within the wall create a natural air gap, which helps to regulate the temperature within the building. Finally, rat trap bond provides greater structural strength than traditional construction methods. This is because the interconnected spaces within the wall provide additional support to the structure, making it more resistant to lateral forces such as wind and earthquakes.

Disadvantages: 

While there are many advantages to using rat trap bond in civil engineering, there are also some disadvantages to consider. Firstly, the technique is more time-consuming than traditional construction methods, as each brick must be laid in a specific pattern. Secondly, the technique requires a high level of skill and expertise, as any errors in the laying of the bricks can result in structural weakness or instability. Finally, the technique is not suitable for all types of construction projects, as it is best suited to buildings with relatively low structural loads.

Applications: 

Rat trap bond is commonly used in civil engineering for a variety of applications. It is often used in residential homes, particularly in areas where insulation is important, such as in colder climates. It is also used in commercial buildings, particularly those with relatively low structural loads, such as offices or retail spaces. In addition, rat trap bond is sometimes used in civil engineering projects where the appearance of the building is important, such as in historic restorations or high-end residential projects.

Conclusion: 

Rat trap bond is a masonry technique used in civil engineering for building walls that are thicker than normal. The technique involves laying bricks in a particular pattern that creates a series of interconnected spaces within the wall, providing improved insulation properties and greater structural strength. While there are some disadvantages to using this technique, such as the need for a high level of skill and expertise, it is a cost-effective and practical solution for many types of construction projects. Whether used in residential homes, commercial buildings, or historic restorations, rat trap bond is a versatile and reliable construction method that has stood the test of time.

 

RAT TRAP BOND MASONRY

RAT TRAP BOND MASONRY

INTRODUCTION: 


The rat trap bond is a masonry technique, where the bricks are used in a way which creates a cavity within the wall while maintaining the same wall thickness as for a conventional brick masonry wall. While in a conventional English bond or Flemish bond, bricks are laid flat, in a Rat trap bond, they are placed on edge forming the inner and outer face of the wall, with cross bricks bridging the two faces. The main advantage of the Rat-trap bond is the reduction in the number of bricks and mortar required as compared to English/ Flemish bond because of the cavity formed in the wall. The cavity also makes the wall more thermally efficient. This also reduces the embodied energy of brick masonry by saving a number of bricks and the cement-sand mortar. It is suitable for use, wherever one-brick thick wall is required. Since its original dissemination in Kerala in the 1970sby architect Laurie Baker, rat trap bond has been extensively used in every category of building from large institutional complexes, community buildings. Government offices/village panchayats, individual homes both for high income and middle income and also in government-supported EWS housing programs. The following figure shows the basic layout difference in the traditional English/ Flemish Bond Masonry methods Vs Rat Trap Bond Masonry.

Fig.6: Various Bonds in Brick Masonry

 CONSTRUCTION DETAILS:

The following Flowchart explains the general schematic of the wall construction process

using Rat Trap Bond Masonry:

                        Chart 1:  Rat Trap Bond Masonry Construction Process

 BENEFITS & ISSUES:

1. By adopting this method of masonry, you can save on approx. 20-35% less bricks and 30-50% less mortar; also this reduces the cost of a 9-inch wall by 20-30 % and productivity of work enhances.
2. For 1 m3 of Rat trap bond, 470 bricks are required compared to the conventional brick wall where a total of 550 bricks are required.
3. Rat trap bond wall is a cavity wall construction with an added advantage of thermal comfort. The interiors remain cooler in summer and warmer in winters.
4. Rat-trap bond when kept exposed, create aesthetically pleasing wall surface and cost of plastering and painting also may be avoided.
5. Rat trap bond can be used for load bearing as well as thick partition walls.
6. All works such as pillars, sill bands, window and tie beams can be concealed.
7. The walls have approx. 20% less dead weight and hence the foundations and other supporting structural members can suitably be designed, this gives an added advantage of cost saving for the foundation.
8. Virgin materials such as bricks, cement, and steel can be considerably saved upon by adopting this technology. It will also help reduce the Embodied Energy of virgin materials and save the production of Green House Gases into the atmosphere.
9. In the case of more structural safety, reinforcement bars can be inserted through the cavity till tile foundation.

There are some issues though which have to be dealt with or kept in mind before the commencement of construction work during the planning stage. These are mentioned below:

1. Service's installations should be planned during the masonry construction if not exposed.
2. It is most suited where good quality bricks with straight and sharp edges are available -better avoided when good quality and uniform size bricks are not available
3. If the mason is not skilled enough, cement mortar can get wasted by falling into the wall cavity.
4.  Needs pre-planning in case of concealed electrical conduiting because chasing brickwork, like in conventional practice, is not possible. However, this can be taken care of by identifying a location of wiring and plumbing in the design and planning stage, so that solid courses of brickwork may be provided in masonry where the conduits will run.

DOs & DON’Ts: 

Before starting the actual construction work, and during the construction progress, there are some checklist items to be observed with care. The critical factors that affect the final quality of the Brickwork Wall made in RAT TRAP BOND are:

1. Curing

2. Quality of Bricks

3. Not used for buildings having more than two floors

4. Quality of sand

5. Availability of skilled mason

Table 4: Dos & Don’ts

Sr. No.	Dos	Don’ts
1	Curing should be done for seven days	Fine sand should not be used for Masonry
2	Cavity should be broken after six layers	Mortar should not be left in cavities
3	Brick should be completely soaked in water before using for masonry
4	Mortar should be used within 30 minutes of adding water to the mix
5	Brick bats should be used at corners and T — Junctions

PERFORMANCE VALIDATION: 

• Rat trap bond can be very easily adapted for earthquake/seismic strengthening i.e. provision of horizontal tie bands and vertical reinforcement in the brickwork cavity.

• The rat trap bond technique has been validated by the Department of Civil Engineering, Anna University Chennai. The results conclude that "the rat-trap bond wall can be safely used for low-cost housing having 2 stories with a short span not exceeding 4.2 m and with storey height not exceeding 3 m, using bricks of minimum compressive strength 50 kg/cm2 with cement mortar 1:3.

•  Rat trap bonded brick masonry has been widely used in all parts of the country. It's excellent weathering over the past 30 years is the best performance guarantee. Importantly, an unplastered brick wall in rat trap bond masonry requires very little recurring maintenance cost since there is no external plaster/painting.

DESIGN AND CONSTRUCTION

Rat-trap bond masonry can be used to construct a small double storeyed residential building in load bearing construction, using the specific construction details which are followed in this technique. The principal requirement for rat-trap brickwork is the availability of good quality bricks.

THE GUIDING PRINCIPLE: 

The following can be taken as guiding principle for the strength of bricks for Rat-trap brickwork:

The data presented here is for Short Span not exceeding 4.2 meters, and Roof/ Floor Loads as per IS 875.

Table 5: The Strength Requirement Guide

Sr. No.	Type of Building Construction	Recommended Compressive Strength of Bricks
		Best Practice	Minimum Allowable
1	1 Load bearing, double storied	More than 50 kg/cm2	40 kg/ cm2
2	Load bearing, single-storied	More than 40 kg/ cm2	35 kg/ cm2
3	Infill masonry in frame structure, no restriction on number of storey	Minimum 35 kg/ crn2	--

THE CRITERIA FOR SELECTION OF BRICKS: 

• Although regional variations in the size of bricks are inevitable, the acceptable sizes for the bricks (in the Indian context) are — Length 220-250 mm, Width 100-115inm and Height 65- 75mm.

• The brick should be rectangular with straight and sharp edges.

• It is important that there should be uniformity in the brick size, so that the brickwork can be designed and constructed in a modular pattern and has good strength and finish.

For mortar, the cement-sand proportion depends on the quality of the brick and the building design which determines the load on the masonry. As a guiding principle, a 1:5 (cement: sand) mortar is recommended for compressive strength of brick not less than 50kg/cm2 and 1:4, if the strength is between 35-50 kg/cm2. A thickness of 1/2" is recommended for the mortar joints, however, a slight reduction in the thickness of vertical joints is allowable because the contact area is much smaller at the side of the brick than at the bottom and top. Care must be taken to ensure that the entire vertical joint is filled with mortar; otherwise, the brick masonry wall will be prone to leakages.

As per design principles of conventional masonry, the corners and the openings represent the weak areas in masonry and should be designed for adequate strength, depending on factors like building design and the seismic strengthening requirements. Therefore, all masonry corners and ends of openings in rat-trap brickwork are constructed solid, without any cavity.

MODULAR DESIGN: 

To ensure maximum advantage of the technique, it is preferable that the masonry is designed in a modular pattern at the design stage itself, after the prevailing brick size available for use has been ascertained. For best rat-trap brickwork, there should be no half bricks/ quarter bricks used in brickwork, unlike their common use in conventional brickwork. This will disturb the staggering of joints in rat-trap brickwork and affect the integrity of brickwork.

Fig. 7: 1 Module of Rat trap Bond Masonry

MASONRY AT JUNCTIONS: 

To improve earthquake resistance, the Rat-trap masonry walls can be reinforced with steel bars at all corners, around openings (door and windows), T-junctions and filled with a M20 concrete. The diameter of reinforcement depends on the number of storeys, storey height, seismic zone, importance of building and soil type. It should not be less than 12mm.

Fig. 15: Masonry & Reinforcement at 'T' & Junctions

In addition to vertical reinforcement, reinforced concrete bands can be provided at three levels —sill, lintel, and roof level. These bands, typically with 2 bars of 8mm dia, can be provided like an open or a concealed element to tie the structure together with vertical reinforced masonry for earthquake resistance.

CURING:

The walls are mostly exposed to wind and sunshine which will dry out the moisture in the mortar joints which will prevent it from hardening adequately. To prevent this from happening, all brick masonry needs regular curing for at least 7 days. A brick wall needs to be cured for at least 7 days.