Jan/100
Snow and ice – a bad combination for your home.
ICE DAMS
Figure 1. Cross section of a one-and-a-half story house with an ice dam.
What is an ice dam?
An ice dam is a ridge of ice that forms at the edge of a roof and prevents melting snow (water) from draining off the roof. The water that backs up behind the dam can leak into a home and cause damage to walls, ceilings, insulation, and other areas. Figure 1 shows a cross section of a home with an ice dam.
What causes ice dams?
There is a complex interaction among the amount of heat loss from a house, snow cover, and outside temperatures that leads to ice dam formation. For ice dams to form there must be snow on the roof, and, at the same time, higher portions of the roof’s outside surface must be above 32° F while lower surfaces are below 32°F. For a portion of the roof to be below 32°F, outside temperatures must also be below 32°F. When we say temperatures above or below 32°F, we are talking about average temperature over sustained periods of time.
The snow on a roof surface that is above 32°F will melt. As water flows down the roof it reaches the portion of the roof that is below 32°F and freezes. Voila!—an ice dam.
The dam grows as it is fed by the melting snow above it, but it will limit itself to the portions of the roof that are on the average below 32°F. So the water above backs up behind the ice dam and remains a liquid. This water finds cracks and openings in the exterior roof covering and flows into the attic space. From the attic it could flow into exterior walls or through the ceiling insulation and stain the ceiling finish.
Nonuniform roof surface temperatures lead to ice dams.
Dealing with ice dams
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- Remove snow from the roof. This eliminates one of the ingredients necessary for the formation of an ice dam. A “roof rake” and push broom can be used to remove snow, but may damage the roofing materials.
- In an emergency situation where water is flowing into the house structure, making channels through the ice dam allows the water behind the dam to drain off the roof. Hosing with tap water on a warm day will do this job. Work upward from the lower edge of the dam. The channel will become ineffective within days and is only a temporary solution to ice dam damage.
- Long-term action:
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- First, make the ceiling air tight so no warm, moist air can flow from the house into the attic space.
- After sealing air leakage paths between the house and attic space, consider increasing the ceiling/roof insulation to cut down on heat loss by conduction.
Read the full article here.
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Oct/090
Building Tips: Preventing a warped door.
Warped doors are most common during seasonal changes, when there is a rapid change in temperature and humidity (specifically winter months). Warp in most cases is not affiliated to a manufacturing defect; it is simply a product reacting to changing environmental conditions.
In more specific terms “moisture imbalance” is the main cause of warp. This is when the atmosphere on the two sides is different. The stresses on one side of the door are not balanced in direction to the other side. If there is an increase of moisture content on one face but not the other, the side with the higher moisture content will tend to elongate and cause the door to bow. Newly- installed doors should be left open until plaster and cement are fully cured. It’s very important to seal all six sides as soon as possible and seal only if the door is straight. When the door is straight the moisture is balanced inside the door. Don’t seal warped doors, this will not allow the imbalance to correct itself.
In most cases a warped door will straighten out after it has acclimated to its surroundings. We recommend the door be allowed to hang through at least a heating and cooling season to allow it to straighten out. A replacement door installed in the same environment may experience the same problem. Again, the door must be sealed all six sides to prevent the moisture penetration into the product, which can cause warp.
In order to minimize the possibility of warp doors, we recommend the following.
- Doors should be stored in a dry area, do not store in areas such as newly poured concrete or recently dry walled or plastered rooms.
- Doors need to be allowed to acclimate to their surroundings. Allow adequate circulation but do not expose to direct sources of heat or cold.
- Doors must be sealed six sides or all warranties are void. This means that the top and bottom of the doors must be coated the same as the stiles and faces of the door. “Dust coating” or overspray is not adequate to properly seal the product. Primed doors such as molded panels must also be painted on top and bottom as well, the prime coat is not an adequate sealer.
All possible steps are taken at the manufacturing facility to minimize the possibility of warp occurring. In addition, following the aforementioned steps should prevent any chance for a warped door.
For more building and construction tips visit our How-To-Library at:
http://howto.millardlumber.com/index.html
