Roof Underlay Leak Problems

Poor Quality Underlayments

• Underlayments come in many versions and quality levels. Felt paper, a common material, comes in thicknesses described through pounds. Roofers typically use 30-pound felt paper, but if they are trying to cut costs they may use lighter-weight versions, which are more subject to wear and may not be enough to prevent leaks for as long as the roof lasts. Plastic membranes can have similar cost issues.

Rot

• While plastic is durable, felt paper and other types of underlayments are subject to rot. This happens when gutters become backed up and water begins to feed back underneath the tiles or shingles into the underlay area. The felt paper cannot stay damp like this for long without beginning to rot and eventually fail. This leads to leaks and the underlayment must be replaced to solve the problem.

Improper Installation

• Underlayments must be installed properly in order to function as they were intended. If they are not fastened down correctly, water may still be able to slip through. Also, if roof tiles are installed incorrectly over the underlayment without sufficient headlap, the underlayment may be more exposed to the elements than it should be and will wear out more quickly.

Punctures and Other Issues

• The underlayment may be working properly, but interference can ruin even a good underlayment. This is true of plastic membranes installed underneath tiles. If a repairman or homeowner walks across a tile roof, their added weight may puncture the membrane. The holes created can become leaks in wet weather.