Damp in a Converted Garage: Could the Door Be the Cause?
Damp is by far the most common complaint for those homeowners who convert their garages into either work or live space. After a conversion is finished, there have been reports of dampness evidenced by condensation on walls, an offensive musty smell, and visible moisture on the garage floor. Before assuming that your garage is structurally compromised, evaluate the garage door itself.
The original garage doors are designed to keep weather out of an unfinished space. They were not designed as components to seal garage interiors from the elements and to create a vapor barrier for closed systems. Garage conversions alter the internal environment significantly. You create an environment with introduced heat sources and controlled ventilation that result in warm, moist air coming in contact with cooler surfaces. If the door isn’t also upgraded to match, it becomes a major weak point in the building envelope.
Dampness due to cold bridging can affect both modern steel doors and older timber doors. In both cases, the doors conduct cold from the exterior to the interior. When warm, moist air comes in contact with a cold surface, condensation will form, and this will occur on cold frame glass and steel doors as well. Once it begins to condense and run down the door, it will soak into the floor and produce the damp or musty smelling conditions that are commonly attributed to either an elevated dampness condition or a leaking roof.
The fix is either a thermally broken door frame or, better still, a fully insulated door system where the frame and panel are engineered as a single insulated unit.
Failed Seals
On an average up-and-over garage door, the rubber or brush seal at the bottom of the door is designed to prevent rain from blowing in below the door. Unfortunately, these deteriorate after about five to ten years and are often left un-replaced. Missing a seal allows rain (and moisture in general) to enter at ground level. With a solid floor, moisture will travel up through the screed along the wall and appear as dampness at the base of the wall.
Replacing these seals is a relatively inexpensive repair, but since the other seals also degrade, it is a good idea to check those as well.
Single Skin Panels
Many older garage doors, including the standard up-and-over steel garage doors, are single skin panels – a skin of steel with no insulation. In terms of thermodynamics, a single skin door is effectively an open hole in the wall. This will result in the cold surface of the door condensing and generating surface moisture for most of the winter.
The direct remedy for this is to replace the door with a thermally insulated door, be it a sectional garage door, foamed panels, an insulated rolling door, or even a side hinged door.
What to Expect From a Replacement Door
When auditing the existing door, if you find it is exacerbating the damp issue, then look for the following features when replacing the door.
A replacement door should include:
● 40mm foam core
● Full perimeter seals
● Thermally broken frame
● Insulated frame constructed of two separate skins of steel and insulation rather than a single steel skin
A replacement door must take into consideration better seal construction to improve thermal performance, minimise the movement of moisture into the living space and improve natural ventilation. Natural ventilation is required to eliminate moisture in a converted living space due to sources such as cooking odors from connected kitchens, utility areas, and even from occupants breathing. So, when replacing the door to meet improved thermal performance requirements, consider investing in a heat recovery ventilation system, or minimally a trickle vent system, to allow controlled flow of fresh air.
No matter how well a new door seals, it restricts airflow. Consider how the best solution may be to encourage airflow and improve ventilation to control moisture buildup.
Getting expert advice is imperative when attempting to identify the source of damp in an enclosure. If the source of damp appears to be centered around the loss of thermal performance at the door opening, then it is likely to be the source of moisture around door opening, especially if dampness is observed on the floor along the door opening and adjacent wall.
A specialist installer can evaluate your existing door and determine if a replacement, resealing, or thermal upgrade is the most economical solution for your conversion.