Rodent Entry Points In Roofs And Attics – Part II

Part II of Rodent Entry Points In Roofs And Attics – Preventative Measures

In a recent article, we discussed some of the most common methods of rodent entry into building roof attics.  Even though the word “flat” indicates that there is no slope to the roof, all flat roofs should have some degree of slope or grade.  Essentially, most roof manufacturers, as supported by the building code, require the roof to have a minimum grade of 1/8 inch per linear foot at all locations.  The historic row homes of Washington DC were mostly built over 100 years ago, so in many cases the original construct may have transformed or deteriorated to some extent. The required grade or slope built into the substrate framing may still not be preserved and intact as it was originally built and or because most of these buildings were originally built in historic times, as well, there might be anomalies or idiosyncrasies where proper grade was not factored into all locations of the original roof deck layout.  

Last week, we wrote an article which looked closely at the transition between a roof termination and the gutter and showed areas of missing drip edges. A similar layout and configuration of building materials in a rear termination assembly is required at rowhomes as well. However, the relatively thin and light gauge metal flashing required to span the transition between the flat roof and the rear gutter is easily manipulated and bent by small animals.

You can see the previous article referenced at the following link:

Rodent Entry Points In Roofs And Attics – Part I

Roof Fascia Is A Perfect Rodent Entry Point

By-and-large though, most rowhome roofs will start out relatively high in the front and then get relatively low in the back. You may even notice in a particular rowhome, especially where there is a rear addition, that the top floor rear rooms have very low ceilings. This difference in ceiling height is specifically intended to accommodate the slope of the roof so that there is continuous or uninterrupted grade from the building front to the back or rear.  This is a particularly difficult constraint for building additions. 

The termination of the roof is a  complicated area of construction because the material types change and transition at that location. The roof itself terminates and then at that point water must be collected and conveyed away from the building through a gutter and downspout rain collection system.  To mount the rain collection system and terminate and cover the edge of the substrate framing, generally a fascia board is used at the rear termination of the roof. However, the fascia board is a wood element, generally between the top of the masonry where the wall and the modified bitumen, built up roof, TPO, or epdm roof membranes terminate. All of those roof membrane types and the masonry at the rear wall itself are generally long lasting and somewhat resistant to weather and moisture. The fascia board, however, is a weak link in the building envelope at that location.

Rodents Can Eat Away The Roof Facia And Metal

Because this particular assembly of materials occurs at the transition from the roof to the exterior wall of the building, it’s a particularly common point of rodent entry. As we mentioned, rodents can aggressively chear and tear their way through building materials and in the picture below you can see examples of just one building where 2 different areas of the facia and metal coping have been eaten through or bent and destroyed by rodents.

roof facia and metal eaten by rodents

The picture below shows this entry point area more closely.   Part of the reason this area was damaged and chewed or clawed by rodents to access the roof attic is that the original or last time of roofing material application at this location were not tightly fitted and just laid in a rough and sloppy manner.

close view of rodent entry points in roofs and attics

How To Prevent Rodents And Small Animals From Entering Roof Or Attic

Smart proactive replacement, construction, upkeep and maintenance of low slope roof systems requires an enthusiastic interest and understanding of waterproofing principles and building science.   Here in Washington DC, historic and modern residential and commercial buildings are extremely expensive and the roof and related systems provide the shield that preserves the building. 

We encourage all of our clients, and all readers of this article and to our blog in general, to prioritize the value of quality construction and building maintenance, and develop a relationship with our company.  You can learn a lot more on our blog.  Feel free to check it out.  If you have questions about the roof and related systems of your building in Washington DC, contact us or fill out the webform below and drop us a line.  We will be in touch if we can help.

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