If you live in a rainy climate, like Florida has been in for the past few months, the exterior walls of your home take a real soaking during wind driven rains. This is particularly troublesome the taller your walls are which is one reason condominiums have had so much difficulty with ‘leaky condo’ issues. Exterior sidings are designed to resist water ingress by either being ‘face sealed’ or ‘rain screened’. Both techniques are effective however the physics involved and maintenance needs are very different.
What is a Face Sealed System?
Face sealed exterior systems are easiest to define in that the siding, or face, of the building is water tight from top to bottom. Face sealed wall systems tend to have a very universal appearance as there should be no joints in material for water to get into. Any joints that may exist will be caulked and sealed. Water that gets behind a face sealed system can cause hidden and expensive damage as there is no path for water to exit and no air circulation to encourage drying. Failures in face sealed systems are particularly troublesome for wood framed buildings as rot and mold thrive in wet environments and they will deteriorate the structure of the building.
Windows, doors, and other protrusions on the exterior of face sealed systems present a challenge as they create weak points in the water proof seal of the building envelope. Multi-story condominiums in particular have had difficulties due to high walls with many windows, doors, vent holes, balconies, and other lifestyle related protrusions. Face sealed buildings require diligent maintenance of caulking, painting, and weather proofing to maintain a water tight seal and are a major part of the ‘leaky condo’ troubles in recent years.
Common exterior materials in a face sealed system include:
- · Traditional Stucco
- · Exterior Insulated Finish System (EIFS)
- · Concrete or Masonry ‘Mass’ Walls
What is a Rain Screened System?
Rain screen systems are designed with consideration for some penetration of wind driven rains. Rain screen systems employ three layers of protection:
- 1. A durable exterior surface for primary water control and resistance to mechanical damage
- 2. An air gap between the primary exterior and the house structure
- 3. A water resistant membrane installed against the home sheeting.
The real science of how a rain screen works lies in the air gap between the house and the siding. When wind drives rain against a building, the lower pressure in the building will tend to ‘suck’ water in. The air gap in a rain screen system provides a neutral pressure gap between the low air pressure in the home and the high air pressure pushing on the exterior. Water that wind drives through the primary exterior loses momentum when it hits the air gap, and falls inside the gap to where it can safely exit the building. The gap also allows for air circulation to encourage drying of all building materials.
On taller rain screened buildings, a horizontal seam of ‘Z’ flashing is often used to separate each story of exterior into separate water control zones. This reduces the total water flowing to the bottom of the building and limits repair expenses if one section of the system fails.
Common exterior materials in a rain screened system include:
- · Fiber Cement Boards (Hardieboard)
- · Veneer Brick or Masonry
- · Some installations of EIFS and Stucco
While not officially a ‘rain screened’ system, some siding products like lapped wood, shingles, or vinyl siding enjoy some of the benefits of rain screening. These products have an inherent air gap behind the face of the material that is ventilated and allows for drainage. These attributes allow them to perform similar to a rain screen system and are considered acceptable alternatives in most rain climates to a comprehensive rain screen.
How Can I Spot if a Building is Rain Screened?
Identifying a rain screened building is about identifying building materials and the install methods. Rain screen systems require an air gap behind the material with drainage and pressure equalization holes.
- · In a brick veneer rain screen, there are drainage holes along the bottom course of bricks (look for missing grout between bricks) and there should be similar holes at the top of the system under a roof overhang or flashing.
- · Hardieboard (fiber cement boards) are nailed horizontally onto vertical wood strips that define the air gap. Flashing at the bottom and top of the course of material allows for drainage and air flow.
- · Stucco or EIFS rain screened systems have flashing at the top and bottom creating ventilation for the air gap beneath. Do not confuse horizontal design treatments in a face sealed system for a properly flashed air gap.
- · On buildings over two stories, look for uniform horizontal lines around the building separating each story of the building exterior into separate rain screened zones. Again, don’t confuse horizontal design elements (decoration) in a face sealed system with a proper horizontal rain screen flashing detail.
What Does a SitePro Home Inspector Look for with Rain Screens?
Rain screens indicate advanced thought by the builder into protecting the building from future water damage. SitePro Home Inspectors will identify if a home exterior is face sealed or rain screened in their report. On buildings over two stories, they should be providing caution to buyers of face sealed homes that the building will require diligent maintenance to help prevent water ingress.
SitePro Home inspectors will confirm the correct use of materials, comment on condition of maintenance, and should highlight to home buyers or owners about any deficiencies or upcoming repairs that may be needed to the exterior. Unfortunately, damage from water ingress cannot solely be confirmed through visual observation and often damage is not visible at all which is a limitation for all SitePro home inspectors and a risk for home buyers. Rain screened systems have lower risks of water ingress which is why home buyers should be encouraged to look at rain screened buildings in wet climates.
Even with all the best investigation practices by home buyers and SitePro home inspectors, buying a home always comes with risks about future maintenance and unexpected damages. As such, it is important to reduce your risk of unexpected expenses by choosing well built and maintained homes.
- · For Condo buyers - If you are looking at a building over 2 stories in a wet climate, look for a rain screened building. Larger building faces have higher risks of water ingress and damages can be very expensive to repair.
- · For typical one or two story house buyers - Rain screens are an excellent recommendation however vented cladding is also a good material. Risks to face sealed issues are lower in two story houses than for taller condos and face sealed systems like traditional stucco have had a good track record over time. With regular homeowner maintenance and good roof overhangs, house buyers can mitigate some risks of damages.
Buying a home is a complex process with high risks. A home inspection by a professional home inspector should always be part of your risk reduction strategy so you can move into your new dream home knowing it will be safe and solid. Contact SitePro
Van Hibberts, CMI
Certified Residential Building Code Inspector ICC-5319905
Florida-State Certified Master Home Inspector Lic. #HI89
Florida-Certified Wind Mitigation Inspector
203(k) FHA/HUD Consultant #A0900
WDO Certificate #JE190791
362 Gulf Breeze Parkway, #214
Gulf Breeze, Florida 32561
850.485.3209 (Cell / Text Msg)
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