Did you know that roofing felt is often used on walls? In fact, this material provides a layer of protection on walls, just like it does against the elements on your roof. The question is whether using the felt is worthwhile for your purposes. We explore the topic to provide some insights and answers below.
What is roofing felt?
Roofing felt is made of several layers. These layers include the base of natural or synthetic materials. This base is often made of wood, cellulose, fibreglass or polyester. It is then soaked with bitumen or another type of protective coating as water resistance. Although the bitumen is made of asphalt and can keep water from penetrating the felt fibres, the material can still breathe.
Why use roof felt?
Roof contractors use this felt material because it protects the structural decking, the wood covering your home’s rafters. Placed atop the decking and beneath the shingles, the felt helps extend the lifetime of your roof by protecting it from the damage caused by water. It also prevents leaks into your house. At the same time, having felt installed beneath the shingles makes the finished roof more attractive.
Helpful Attributes of Roof Felt
Below are the beneficial attributes of roof felt:
Roof felt is known for its water-repellant capabilities. In fact, it helps make water drain off of the roof, keeping it from leaking into your home. As a result, it prevents moisture damage, rot, mould and leaks because of snow and wind-driven rain.
Prevention of Damage from Melting Ice
In cold climates with frequent sub-zero temperatures, ice or snow dams can form on the roof. Because heat rises from inside the home toward the roof, this heat melts the accumulated snow or ice and creates water runoff. The water can seep into nooks in roof, then down into the home. When this happens, you experience leaks and damage to walls, ceilings and insulation. Roof felt, along with waterproof membranes, provide protection against these leaks and improved water resistance.
The shingles of your roof are your home’s first defence against weather and debris. But having felt under the shingles provides even better protection, like a second line of defence. If shingles break off during a storm, the felt keeps the roof deck safe from water until the shingles are replaced.
Improved Fire Rating
Shingles alone do not typically meet fire rating requirements. With roof felt in place, your home has improved defence against fire and can meet inspection requirements. It is important to use felt and shingles that are compatible with each other and building codes, however.
Having roof felt in place levels the surface for shingle installation. This helps shingles lie flat with uniformity.
Prevents Stains from Wood Resin
Some types of wood leach resin over time. This process can stain your roof shingles or otherwise compromise them. But the felt acts as a layer of protection between the wood roof deck and shingles, just like it keeps water from draining downward from shingles onto the deck.
Now that you can see the typical benefits of roof felt when it is applied to the roof, you can also understand how it can prove beneficial beneath wall surface materials.
Using Roof Felt on External Walls
It is common for builders to use roof felt as a water-resistant layer between wall sheathing and the wall covering. This layer keeps moisture from seeping into the home’s interior. As a result, using felt can prevent rotting underlying materials.
To use roof felt on exterior walls, simply apply the material on all outside surfaces. Also install it around windows using roof nails. Then apply siding, veneer or brick.
Felt Paper on Interior Walls
Using roof felt paper on inside walls is also common, particularly beneath plaster. If you apply plaster directly to wood, the plaster cracks over time as the wood expands and contracts. Roofing felt does not expand or contract, so it provides a stable surface for the plaster, acting as a slip plane.
Roof felt also provides water resistance by keeping water vapours absorbed by the plaster from leaching into the wood. Felt keeps the wood isolated from the plaster and allows the plaster to absorb and release moisture without damaging the inner wall structure.