What Are Wall Gables?

What are Wall Gables?

Cavity wall gables refer to the triangular section of a wall that extends from the top of the wall plate to the ridge of the roof. This section is crucial in ensuring proper insulation and waterproofing, especially when the cavity insulation terminates part-way up. Ensuring that the insulation and waterproofing measures are correctly implemented is vital to prevent early deterioration, structural weaknesses, and water damage.

Can Water Be Fed Behind a Render Coat Across the Gable?

One of the key considerations in cavity wall gable construction is whether it is acceptable for water to be directed behind the render coat across the gable. This approach can lead to several issues, including water retention, early deterioration, and potential delamination. Freezing temperatures can exacerbate these problems, causing cracking and structural failure over time.

Version 1: Built into the Inner Skin

In this version, the Damp Proof Course (DPC) is built into the inner skin, dropping down across the cavity and projecting through the outer skin, which is rendered. While this may initially seem effective, several weaknesses are inherent in this design:

• Structural Weakness: The entire gable triangle rests on the DPC, creating a line of damp regardless of the presence of weep holes.
• Cracking and Structural Failure: Cracks can develop along the DPC line, leading to potential structural failure.
• Witness Line of Damp: A visible line of damp can form, indicating water penetration and retention issues.

 

Version 2: Projects Partway Through the Exterior Skin

In the second version, the DPC arrangement is similar but with the lower horizontal section passing only partially through the exterior skin. This modification offers some improvements but still presents significant concerns:

• Reduced Structural Weakness: Although the outer skin is weakened to a lesser extent, it is still vulnerable.
• Water Seepage: Water from the gable triangle feeds directly into the middle of the outer skin, directing water behind the render coat.
• Potential Delamination: Concentrated water sources can cause damage and delamination of the render.

 

Version 3: Insulation Without Outer Skin Interruption

The third version provides a more satisfactory solution by protecting the top of the insulation without interrupting the outer skin. This approach ensures that:

• Natural Water Dissipation: All water penetrating the outer skin can naturally continue gravitating and dissipating without accumulating on the DPC.
• No Weep Holes Required: The design eliminates the need for weep holes, reducing potential entry points for water.
• Uninterrupted Outer Skin: The outer skin remains structurally sound and uninterrupted, preventing cracking and localised water accumulation behind the render.

 

Version Comparison

When comparing these three construction techniques, it is evident that Versions 1 and 2 present significant disadvantages. They compromise the structural integrity of the building and increase the risk of water damage. In contrast, Version 3 promotes a more satisfactory structural and waterproofing arrangement, ensuring better functionality and durability.

Floppy Roll DPC and Rigid-Profile Dropcloak

In the context of cavity wall gables, the type of DPC used is crucial. A floppy roll DPC is often unsatisfactory due to its inability to maintain shape and profile consistency. On the other hand, using a preformed rigid-profile Dropcloak from Cavity Trays Ltd offers several benefits:

• Shape Retention: The rigid-profile Dropcloak retains its shape and ensures consistent performance.
• Waterproofing Efficiency: It prevents water from accumulating behind the render coat, reducing the risk of damage and delamination.

 

Structural and Waterproofing Benefits of Version 3

Option 3, where the DPC protects the insulation without punctuating the external skin, provides several key benefits:

• Structural Continuity: The gable triangle does not rest on the DPC, maintaining structural integrity.
• No Cracking or Witness Line: The design eliminates horizontal cracking and visible lines of damp.
• No Weeps Required: The absence of weep holes reduces potential water entry points.
• Suitability for Exposed Sites: The robust design is well-suited for highly exposed sites.
• Versatility: It can be used with various external skins, including brick, stone, and render.

 

The Importance of Proper Cavity Wall Gable Construction

Proper construction of cavity wall gables is essential to ensure the long-term durability and performance of a building. By selecting the right materials and construction techniques, builders can prevent common issues such as water retention, structural weakening, and render delamination.

Type CD Cavity Dropcloak

The Type CD Cavity Dropcloak, manufactured by Cavity Trays Ltd, is a highly effective solution for cavity wall gables. As the longest-established cavity tray company, Cavity Trays Ltd offers products that ensure shape retention, profile consistency, and superior waterproofing performance. By using the Type CD Cavity Dropcloak, builders can achieve a reliable and durable construction that protects against water damage and structural weaknesses.

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Learn More

Cavity Trays is an industry leader in the design, manufacture and supply of damp-proofing, cavity closers, ventilation, and other specialist products in the construction sector.

We have decades of experience helping businesses comply with all relevant building regulations. To learn more about our Wall Gables, including dimensions and installation instructions or to enquire about any of our products, get in touch with us today or call us on 01935 474769.