Treating the Roofline and DPC on a Retrofit

Retrofitting an older property often unveils many challenges. Treating the roofline and damp proof course (DPC) frequently tops the most common problem areas. These components are crucial for the integrity and longevity of any building. However, they are also the most susceptible to neglect and deterioration over time. Any thermal envelope or building section will be susceptible to damage or other problems. This includes corners and window reveals. However, these areas can be treated with various forms of beading. High-quality uPVC beading will strengthen reveals and prevent water ingress. The roofline and DPC are altogether more complicated, not just due to legislation.

What is the roofline?

The roofline is critical to a property's structural integrity and aesthetic appeal. It comprises various components such as fascias, soffits, guttering, and bargeboards. These elements work together to protect the building from water ingress and help manage the flow of rainwater away from the structure, preventing potential damage.

Roofline components

1. Fascias - The vertical boards attached to the edges of the roof rafters. Their primary role is to support the lower edge of the bottom row of tiles and carry the guttering. Fascias must be strong and robust as they support significant weight, especially during heavy rainfall.
2. Soffits - Soffits are the boards fitted beneath the fascia boards. They cover the underside of the roof, which overhangs the walls. They are vital for roof ventilation and prevent condensation in the roof space, which can lead to timber decay.
3. Guttering - The guttering system collects rainwater from the roof and diverts it from the foundation. Properly functioning gutters are essential to prevent water damage to the building's exterior and foundations.
4. Bargeboards - These boards are often decorative and are used on the gable end of a house to provide a finish between the roof and the wall. Bargeboards also enhance the visual appeal and protect the roof timbers from weather elements.

Assessing the condition of the roofline

A comprehensive inspection should be conducted to assess the condition of the roofline. Assessing the condition of these critical areas is the first step in any retrofit project. This initial review helps identify existing and potential issues that could escalate if not addressed promptly. A thorough examination can reveal hidden problems such as blocked guttering, inadequate ventilation, or a breached DPC, setting the stage for a more successful retrofit.

• Signs of physical damage such as cracks, rot, or detachment.
• Evidence of water damage or leaks, especially around the guttering system.
• Blocked or overflowing gutters which can indicate poor maintenance.
• Deterioration in the sealant or joints might compromise the waterproofing integrity.

Treating the roofline

Given the crucial role of the roofline, it is imperative to treat it correctly. Mistreatment can result in issues like water ingress, which can cause structural damage.

Extending the roofline

• Adding overhangs: Extending the eaves protects the walls and foundations from rainwater splashback.
• Improving rainwater management: Longer overhangs allow for more effective positioning and sizing of gutters and downpipes, which is crucial for managing increased water flow from larger roof areas.

Eaves protection systems

Eaves protection systems are designed to improve the durability and functionality of the eaves (the roof's lower edges).

• Prevent sagging and water damage: They support the eaves and prevent the sagging of roofing felt, enhancing the roof's ability to shed water effectively.
• Improve underlay support: This is particularly beneficial in preventing ponding behind the fascia board, thus extending the life of the roofing material.

Upgrading guttering and downpipes

Upgrading the guttering and downpipes is often necessary during a roofline retrofit, particularly if the existing system is inadequate or in poor condition.

• Increasing capacity: Larger gutters and downpipes can handle more significant volumes of water, reducing the risk of overflow during heavy rainfall.
• Improving materials: Using durable materials like cast iron for heritage properties or modern UPVC for more contemporary buildings can enhance longevity and reduce maintenance needs.

Installation of soffit vents

Retrofitting soffit vents or improving existing ventilation systems in the roof can be crucial, especially in older buildings that may not meet current ventilation standards.

• Prevent condensation: Adequate ventilation helps keep the attic dry, preventing condensation that can lead to rot or mould growth.
• Improve energy efficiency: A well-ventilated roof space helps maintain steady temperatures, reducing the burden on heating and cooling systems.

When choosing materials for retrofitting the roofline, compatibility with existing materials is essential to ensure structural integrity and visual coherence. Materials should be selected for their aesthetic compatibility and performance characteristics, ensuring that all roofline components work harmoniously to protect the building.

Roofline closure systems and legislation

The incoming Roofline Closure Systems will qualify many of the questions posed throughout the industry regarding the roofline. Industry training is due to take place soon, with DESNZ disseminating an industry letter to the industry. Through our partnership with EWI Pro, we will be able to provide detailed documents and training to installers on the treatment on the roofline. However, for now, rooflines are to be treated with a degree of caution. We will also publish a new blog about the Roofline Closure Systems.

Treating the DPC

The damp proof course (DPC) is a critical barrier designed to prevent moisture from the ground from rising through the walls by capillary action. In retrofit projects, especially in older properties, addressing the DPC is vital to prevent structural damage and maintain a healthy living environment. Before any corrective action is taken, it is essential to accurately diagnose the existing DPC state.

• Visual inspections: Checking for visible signs of moisture, such as damp patches, tide marks, or salt efflorescence on walls.
• Moisture readings: Using moisture meters to detect elevated dampness levels in wall materials.
• Investigative digs: Sometimes, small sections of the external ground may be excavated to locate and examine the condition of the original DPC.

[caption id="attachment_75186" align="aligncenter" width="768"] Moisture testing of existing walls[/caption]

Methods of retrofitting a DPC

Depending on the findings from the assessment, several techniques can be employed to retrofit a DPC effectively:

1. Chemical DPC injection: This is one of the most common methods today. It involves drilling holes at regular intervals along the mortar course and injecting a silicone-based chemical which repels water. This method is effective for many types of masonry and is relatively quick and cost-effective.
2. Physical membrane installation: In some cases, particularly during major renovations, a physical DPC layer of plastic or lead sheeting can be inserted into the walls. This method can be more disruptive as it may require substantial removal of brickwork or stonework but provides a reliable barrier against dampness.
3. Electro-osmotic systems: This method uses a small electric charge to repel water molecules from the wall surfaces. While less common, it can be useful in structures where chemical injections or physical barriers are not feasible.
4. Cavity wall trays: If rising dampness is compounded by penetrating dampness due to defective external wall ties or cavities, installing cavity trays can help. These trays collect and redirect water from the cavity before reaching the internal wall.

[caption id="attachment_68175" align="aligncenter" width="1000"] A DPC in place in a cavity wall[/caption]

Insulating below the DPC

XPS's robust closed-cell structure ensures minimal water absorption and high compressive strength, making it ideal for below-grade installations where durability and moisture resistance are critical. For effective insulation below the DPC, XPS should be carefully installed to avoid bridging the DPC, thereby preventing moisture from wicking into the wall structure. The integration of XPS should be complemented with EWI Pro Aquabase. Following EWI Pro Aquabase, EWI Pro Mosaic Render can be applied as a decorative and protective topcoat. This render enhances the building's aesthetic and contributes additional weather resistance, safeguarding the exterior against environmental elements. Available in various colours, the mosaic finish allows for aesthetic customisation to match or enhance the building’s façade.

Aquabase (EWI-226) - 25kg

Brand: EWI Pro

£28.70 Incl. VAT

£23.92 Excl. VAT

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