This month I came across 4 properties with different types of sagging roofs. So here we go.
A single-family roof framing is commonly comprised of rafters, which are the sloped members that the roof deck is nailed to, and ceiling joists or rafter ties, which are the horizontal members. When you are standing or sitting in an attic the rafters are seen above you and the ceiling joists below you. These members are commonly configured such that they form a triangle with two sloped topsides and one flat bottom side. The triangle is a very interesting shape because no matter which direction you apply a load or a pressure, the other two members will provide support.
So why do roofs sag?
Weakened roof material
Water damage can be a major cause of roofing problems. It can cause sections of your roof to rot and weaken. There are lots of ways snows and rain can infiltrate your roof. Moisture can find weaknesses in your roof and settle there. As it sits, it causes the roofing material to deteriorate. It can even cause mold and mildew to develop, further weakening it. Your roof has some protection from the elements – shingles and flashing, for example – but that doesn’t mean that it’s impenetrable. Make sure your roof is properly draining rainwater off of it. Have professional do periodic checks for signs of water damage. Poor ventilation is another way your roof material can weaken. Poor ventilation means that air isn’t circulating which means that moisture is sitting stagnant on your roof.
Faulty Roof Material
The quality of your roofing material plays a big role in determining how long it will last. A roof constructed using asphalt shingles may be less expensive, but it won’t last as long as one that uses, say slate, which can sometimes last 100 years. This applies to all of the elements that come together to form the roof – beams, nails, etc. Also, the best roofing materials in the world won’t matter if they are not installed properly. Make sure that whatever roof work you have done is done by a professional.
Too Much Weight
Snow, ice and rain can cause big problems if they’re allowed to settle and sit on your roof for a long time. Your roof is designed to support a certain amount of weight. It can withstand the occasional snow or rainstorm, but prolonged stress isn’t good for it. The critical factor in determining excessive snow loads on your roof isn’t the depth of the snow, it’s the weight. That’s because wet snow is considerably heavier than dry, fluffy snow. In fact, six inches of wet snow is equal to the weight of about 38 inches of dry snow. The good news is that residential roofs are required by building codes to withstand the heaviest snows for that particular part of the country.
“Theoretically, if your roof is built to code, it’s built to support more than the normal load of snow
You can determine the type of snow you’re getting simply by hefting a few shovelfuls — you should be able to quickly tell if the current snowfall is wet or dry. Local winter storm weather forecasts should alert you to the possibility that snow loads are becoming excessive and a threat to your roof.
How Do I Know There's a Problem?
An indication that the accumulated snow load is becoming excessive is when doors on interior walls begin to stick. That signals there’s enough weight on the center structure of the house to distort the doorframe. Ignore doors on exterior walls but check interior doors leading to second-floor bedrooms, closets, and attics in the center of your home. Also, examine the drywall or plaster around the frames of these doors for visible cracks. Homes that are most susceptible to roof cave-ins are those that underwent un-permitted renovations. The improper removal of interior load-bearing walls is often responsible for catastrophic roof collapses.
The Snow Load Seems Excessive, Now What?
Most home roofs aren’t readily accessible, making the job dangerous for do-it-yourselfers.
Instead, call a professional snow removal contractor to safely do the job. Check to make sure they are licensed and insured — that immediately sets them apart from inexperienced competitors.
Pro crews attack snow removal with special gear, including sturdy extension ladders, properly anchored safety harnesses, and special snow and ice-removal tools. Expect to pay $250 to $500 for most jobs.
Don’t expect (or demand) a bone-dry roof at job’s end. The goal is to remove “excessive” weight as opposed to all weight. Plus, any attempt to completely remove the bottom layer of ice will almost always result in irreparable damage to your roofing.
The Do It Your Self Option
If you have a small, one-story bungalow where the roof is just
off the ground, taking matters
into one’s own hands may be
safe — if you can work entirely from the ground and have the right tools. Long-handled snow rakes work great on freshly fallen snow, and at $45 they are relatively affordable. Look for models with sturdy telescoping handles and built-in rollers, which keep the blade safely above the shingles. Other versions work by releasing the snow from underneath. These models slide between the roof and snow, allowing gravity and the snows own weight to do most of the work. Models range from $50 to $125 or more for unique systems utilizing nylon sheeting. Again, search out models with sturdy adjustable handles. They tend to work their best on light, fluffy snow — the kind that probably doesn’t need to be removed in the first place. You’ll need to anticipate where the snow and ice will fall as you pull it off your roof — you won’t want to pull a load of heavy, wet snow down on top of yourself or any helpers. Remember, the goal isn’t to remove all visible snow and ice, but rather just enough to relieve the excessive load on the roof.