Felt roofing is a practical and widely used solution for flat and low-pitched roofs, but over time, you may notice raised areas, bubbles or blisters developing across the surface. While a small blister may not initially appear serious, it can indicate that the roofing layers are no longer bonded correctly and may eventually contribute to water penetration.
For property owners in Havant, Hampshire, understanding why blisters form can help identify roofing problems before they become more difficult to address. At Havant Roofing Repairs, we inspect felt roofing carefully to determine the cause of the problem and establish whether a local repair or more extensive work is appropriate.
What Are Blisters and Bubbles in Felt Roofing?
A blister is a raised section of felt roofing where part of the material has separated from the layer beneath it. Bubbles can vary considerably in size, from small raised patches to larger areas that are clearly visible across the roof.
These raised sections may contain trapped air, moisture or a combination of both. They can occur between layers of a built-up felt roof or beneath the felt itself, depending on how the roofing system has been installed.
Although a blister does not automatically mean that the entire roof has failed, it should not simply be ignored.
What Causes Felt Roofing to Blister?
Several factors can contribute to blistering. Identifying the underlying cause is important because simply treating the visible raised area may not resolve the problem.
Trapped Moisture
Moisture trapped between roofing layers can turn into vapour when the roof becomes warm. The resulting pressure can cause the felt to lift and form a bubble.
This can happen where moisture became enclosed during installation or entered through a damaged section of the roof.
Poor Adhesion Between Layers
Felt roofing systems rely on appropriate bonding between their layers. If the materials were not adequately bonded during installation, sections can gradually separate.
Poor adhesion may become more noticeable as the roof experiences changes in temperature, moisture and weather conditions.
Temperature Changes
Roofs are exposed to repeated heating and cooling throughout the year. Felt and the materials beneath it expand and contract as temperatures change.
Over time, this movement can place stress on the roofing system, particularly where there are existing weaknesses or areas where the layers are not securely bonded.
Inadequate Roof Preparation
The condition of the surface beneath the felt is important. Dust, dirt, moisture, uneven surfaces or unsuitable preparation can affect how effectively the roofing materials adhere.
If the original installation was not carried out correctly, blistering may gradually become more apparent as the roof ages.
Ageing Roofing Materials
Felt roofing naturally deteriorates with age. Prolonged exposure to weather can reduce its flexibility and weaken the bonds between roofing layers.
Older felt may therefore be more susceptible to cracking, splitting, lifting and blistering, particularly where other defects are already present.
Are Blisters on Felt Roofing a Serious Problem?
The significance of a blister depends on its size, location and condition, as well as the overall state of the roofing system.
A small, intact blister may not immediately allow water into the building. However, raised areas can become vulnerable to damage from foot traffic, weather exposure and continued movement of the roofing materials.
If a blister cracks or splits, water may find its way beneath the felt. Once moisture gets into the roofing layers, the affected area can deteriorate further and potentially lead to dampness inside the property.
For this reason, it is sensible to have persistent or worsening blistering inspected rather than attempting to puncture or flatten it yourself.
Can Blisters in Felt Roofing Be Repaired?
In some cases, felt roofing blisters can be repaired without replacing the entire roof. The appropriate method depends on what caused the blister and whether the surrounding roofing material remains sound.
A roofing professional can inspect the affected area and check for signs of moisture, damaged felt, loose layers and other defects. Where a local repair is suitable, the damaged section can be treated and the roofing system restored as effectively as possible.
If blistering is widespread or the felt has deteriorated significantly, more extensive remedial work may be necessary. A proper inspection helps establish the condition of the roof rather than relying solely on the appearance of the surface.
How Can You Prevent Felt Roofing Blisters?
Good installation and regular roof maintenance can help reduce the likelihood of blistering. Keeping drainage points clear helps prevent standing water, while addressing small cracks, splits and damaged areas promptly can help prevent moisture from reaching the roofing layers.
It is also useful to have a flat or low-pitched felt roof inspected when you notice new bubbles, lifting or other changes to its surface. Early attention can help identify whether the problem is localised or part of a wider roofing issue.
Felt Roof Repairs in Havant, Hampshire
Blisters and bubbles on felt roofing can have several causes, including trapped moisture, poor adhesion, temperature movement, inadequate preparation and ageing materials. The visible blister is only part of the problem, so identifying what is happening underneath the surface is important before deciding on a repair.
At Havant Roofing Repairs, we can inspect felt roofing in Havant, Hampshire and assess the condition of the affected areas. If your roof has developed new blisters, bubbles or other signs of deterioration, contact us to arrange a professional inspection and discuss the appropriate repair.
Call us on: 023 8235 7284
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