If you discover that you have a sag in the roof of your home or building you are probably wondering what caused it and how it should be fixed. Many times sags in a roof are due to excessive deflection or a break in one or more of the structural roof members caused by some type of overload. In Colorado roofs can become overloaded with snow drifting on lower roofs that intersect upper floor walls. In some instances, roof members can deflect or break when they are temporarily overloaded with stacks of asphalt shingles or tiles during re-roofing. Older roofs may experience noticeable “creep” deflection which is a phenomenon where structural wood elements “relax” over time and experience long term permanent deflection under a sustained load.
Roofs can also sag when the attic is not adequately vented. Wood framing can experience significant expansion and contraction under changing temperature and humidity conditions that occur within the attic throughout the year. Wood members that have higher moisture contents typically experience a higher magnitude of long term creep deflection. If the roof is constructed with pre-manufactured trusses the connector plates can become loose over time as the wood containing the embedded plate teeth expands and contracts. If the connector plates pull loose then the connected truss members may pull out of the joints causing the truss to deflect. Loose plates can also result in load transfer to other members of the truss which can lead to cracks, splits or breaks in a truss member.
Mechanically pressed metal connector plates can carry a surprising amount of force but even very small gaps between the plates and the wood surfaces significantly reduces the holding capacity of the plates. In fact a connector plate that exhibits a gap of just 1/16” from the face of the wood loses about 50% of its holding capacity and is subject to failure.
CENSPACE, LLC has engineers who are experts in restoring a sagging roof. Give us a call for a consultation or inspection of your building before deciding to replace that sagging roof.
The usual procedure for homeowners or building owners who finds themselves in need of someone to repair broken roof trusses and roof rafters/joists or sagging roofs is to contact a building contractor or roofing company, who in turn, will likely hire a structural engineer familiar with truss engineering. Most of the roof systems on residential buildings constructed in Colorado after 1970 were built with pre-manufactured (also called “pre-fabricated” or “pre-engineered”) roof trusses, which are typically constructed with 2x4 or 2x6 members arranged in a triangular pattern and connected at the intersecting joints with mechanically pressed metal plates. Most roof systems on residential buildings constructed in Colorado prior to 1970 are “conventionally framed” using an assembly of 2x solid sawn rafters and joists.
A savvy contractor who has experience with trusses and/or conventional roof framing will be able to offer solutions for the repair of damaged trusses or a sagging roof, but ultimately a licensed engineer will have to be retained to provide a definitive solution in order to obtain a building permit and ensure a safe repair design as well as piece of mind for the homeowner. Documentation may also be required if the owner plans to sell the home or building in the near future. It is not unusual or unreasonable for the contractor to bring in an engineer at a premium cost to you.
An alternate, and more cost-effective solution, is to call CENSPACE, LLC directly. We have engineers who can come out to your home or building and inspect damage to the structural framing inside the roof then make sound recommendations prior to getting involved with a contractor. Once the engineer has diagnosed your roof problem, we can provide you a clear estimate for generating stamped repair drawings that can be used to obtain a building permit. At that point you can send the stamped drawings to perspective contractors to bid the construction of the repair work as required. By following this process, you will spend less time with fewer headaches getting your roof repaired safely and more cost effectively.
The short answer is yes but there are several caveats. There are a number of mending plates that you can buy at your local home improvement store. Most of those plates are used for repairing fence posts, reinforcing doors, workbenches or bed frames and similar non-structural applications. Many of these products should not be used outdoors or with pressure treated lumber because they are not corrosion resistant. Some of these products may be adequate for certain structural applications if the steel and connectors are designed and approved by a licensed engineer. Most pre-manufactured mending plates and the connectors are not capable of handling the high forces induced in roof truss members so they must be used judiciously. Hammering on mending plates or to repress existing plates that have punched teeth is NEVER an acceptable structural repair for a truss.
Plywood or OSB gussets with nails (or specific types of screws) are commonly used in lieu of steel mending plates to repair or reinforce truss joints where connector plates are missing, loose or otherwise damaged. It is usually necessary for a licensed engineer, who is familiar with truss design, to size and specify this type of connection. Many times truss repairs are easy enough for the owners to take on by themselves.
CENSPACE, LLC has engineers who are experts in the repair of trusses, so please call us first for a consultation or inspection before attempting structural truss repairs on your own.
How about leaving the existing roof in place and construct a new roof overly using pre-manufactured roof trusses. Flat roofs deteriorate more quickly in harsh climates like Colorado so repair or replacement of flat roofs is more common in these parts. Growing concern for the failure of flat roofs is due to excessive deflections from water pooling on the roof. Initial deflections in the flat roof system allows water to become trapped, which in turn, causes more roof deflection. A vicious cycle is generated which can lead to roof failure if the roof structure is too flexible.
Instead of removing or reinforcing the flat roof system it may be feasible and much less costly to simply add a pitched roof system over the existing flat roof. The new roof can act independently from the old roof or the new roof can be designed to help support the old roof so the ceiling of the building can remain intact. Pitched roof systems as low as 2 /12 (two inches of vertical rise for each 12 inches of vertical run) are relatively stiff and help shed snow and ice from the roof promoting integrity and longevity of the roof.
CENSPACE, LLC has engineers who are experts in flat roof replacement. Give us a call for a consultation or inspection of your building before deciding to replace the old flat roof.
Many homeowners throughout Colorado’s Front Range have replaced their old roof shingles with tiles. Whether this is due to hail damage or a reduction in home owner’s insurance premiums or simply that the old deteriorated shingles no longer provide adequate protection, a new roof improves the value of your home – unless the roof framing was not adequately designed to carry the heavier load of the new tile.
The majority of roofs constructed with pre-manufactured trusses are strictly designed to carry a set dead load considering the weights of materials on a specific roof. Since truss manufacturers are in fierce competition with each other, it is advantageous for the truss manufacturer to optimize the truss designs with as little extra strength as possible so as to provide the best price for their clients. The result is that any moderate increase in loading, say from an asphalt shingle to tile load, could render the existing truss design structurally deficient. Another example of adding moderate roof loading is the addition of solar panels. Truss connector plates or hanger connections may become over-stressed or there may be some type of construction or lumber defect with one or more of the truss members. In addition, sometimes trusses require additional lateral web bracing when the loads are increased beyond the original design load.
CENSPACE, LLC has engineers who are experts in inspecting and approving existing trusses for adding additional loads. Particularly when replacing asphalt roof shingles with heavier tile or adding solar panel. Give us a call for a consultation or inspection of your trusses before deciding to replace those shingles.
Trusses come in a myriad of shapes and sizes not to mention various degrees of structural capacity and quality. In the majority of circumstances most trusses can be modified, through proper redesign and construction/reinforcement procedures.
Older trusses, designed under a previous building code, may not have as much structural reserve capacity as a truss designed within the last 10 to 15 years or so. Long narrow trusses that are more heavily stressed under normal loading conditions, may require more reinforcement than shorter or higher pitched trusses. The original trusses may have some pre-existing construction deficiency or one or more trusses may be damaged; all of which could require additional design and construction work. All of these variables need to be considered before determining the feasibility of modifying existing trusses to create that new ceiling look you are after.
CENSPACE, LLC has engineers who are experts in inspecting existing trusses to determine the feasibility of modifying them and once all the options have been explored and explained to you then we can provide design drawings with step by step procedures for completing the construction. Give us a call for a consultation or inspection of your trusses if you are thinking of raising up that low flat ceiling space to a voluminous cathedral.
PO Box 33573, Northglenn, CO 80233
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