Well if the members you have seen looks like the below, then you must be referring to collar ties. But did you know there are code requirements as to where and how these collar ties must be connected? Section R Collar ties are used to connect opposing rafters in order to resist the ridge uplift cased by wind loads. When it comes to collar tie placement, the code specifies that collar ties are to be located in the upper one-third area of the attic space up near the ridge and shall not be spaced more than 4 feet on center.
The code specifies that a collar ties must not be less than a 1 inch x 4 inch nominal wood member. The minimum connection requirements for collar ties must be per Table R Ridge boards can only be used in roofs with slopes from 3 in 12 up to 12 in Can I remove my ceiling joists?
The next option you can consider in opening up the ceiling frame is to remove some of the ceiling joists or collar ties while leaving the full complement of rafters in place. Typically, this is done by leaving every third collar tie and removing the two in between, as shown in the drawing. You still have rafters 16 in. What's the difference between Truss and Rafter? Trusses and rafters are both assembled ahead of being installed onto the roof. Trusses are assembled in a factory using pre-engineered structures and joints.
On the other hand, rafters are assembled at the construction site. Rafters contain two main outer beams which support the roof structure. How do you build a truss? Cut the bottom cord of the roof trusses. Make the gussets, which are the half-inch thick plywood pieces that will cover the 3 ends of the roof trusses. Start assembling the trusses. It is free and quick. Additional giveaways are planned. Detailed information about all U. Posting Quick Reply - Please Wait.
Similar Threads Are white collar cities look as better than blue collar cities on these forums? Paul, 6 replies. Are collar ties needed these days? User Name. Remember Me. View detailed profile Advanced or search site with. Search Forums Advanced. Page 1 of 3. Advertisements I have not done anything to my attic yet.
Quote: Originally Posted by Rickcin Collar ties do add to the resistance of the rafters and walls laterally to spread as mentioned above, so they basically are not necessary since the ceiling joists provide the same function. Quote: Originally Posted by harry chickpea Chord, not cord. Quote: Originally Posted by turf3 Now you've got nails in shear the strong direction making the joints.
Where rafters are oriented perpendicular to the ceiling joists, rafter ties should be installed just above the ceiling joists. The ties usually rest on the joists. When rafters are installed on inch centers, rafter ties are typically installed at every other rafter. Tension Forces. Rafter and collar ties are subject to enormous tension forces. These forces make securing the ties to the rafter boards a critical issue. The force in each tie increases with the inverse of the slope.
So, the greater the roof slope, the weaker the outward thrust. The load on a structure can be calculated from combining the dead load or weight of the structure itself, the live load that varies for different structures, the snow load, and the wind load. In a simple gable roof, the rafter boards carry the live and dead loads that push both downward and outward against the top of the load-bearing walls. This horizontal outward thrust can be considerable.
To resist this horizontal outward thrust, the International Residential Code calls for each pair of rafters to be securely connected to each other by a continuous ceiling joist, and for a structural ridge beam to be installed for roofs with a slope of less than see illustration below. Where ceiling joists are not connected to the rafters at the top wall plate, joists connected higher in the attic shall be installed as rafter ties, or a continuous tie should be provided.
Where ceiling joists are not parallel to rafters, rafter ties shall be installed. Where ceiling joists or rafter ties are not provided, the ridge formed by these rafters must be supported by a wall or girder. The ends of ceiling joists should be lapped a minimum of 3 inches, or butted over bearing partitions or beams and toenailed to the bearing member.
Where ceiling joists are used to provide resistance to rafter thrust, lapped joists shall be nailed together in accordance with Table R For example, if a house has a slope, the rafters are on inch centers, the snow load is 30 psf, and the roof span is 28 feet, you need eight 16d common nails or 40d box nails at each rafter-heel joint connection.
That's a lot of nails a home inspector can look for. Cathedral ceilings are popular in many homes, but they have special issues with the downward load on the rafters that push outward on the exterior walls.
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