2x12 Bottom Chord Of Attic Truss

When designing attic trusses use floor truss bottom chord instead of 2x10 or 2x12 dimension lumber.

2x12 bottom chord of attic truss.

This reduces truss lumber and bracing as well as field labor. Attic or room in the roof trusses are becoming increasingly popular as they offer increased living space without changing the footprint of the house delivering maximum value to the builder and homeowner. Unfortunately instances of plumbers notching and drilling the bottom chord of an attic truss are all too commonplace. However such guidance cannot be used with a framework such as an attic truss.

Attic trusses have a rectangular shape inside each truss. The lumber is clear and knot free straight grained and very hard. These are referred to as webbing. The bottom chord of the truss which becomes the floor joist of the room can be designed and manufactured in a number of ways.

I m using a good quality bostich framing gun and it doesn t have enough power to fully drive a 10p nail. 30 ft fink trusses 6 12 pitch and 2x4 chords and webs 2 o c. There is industry guidance concerning cutting and notching of joists for cables and central heating pipes. The sad fact is your builder could have installed attic trusses over this garage for just slightly more than what the existing trusses cost.

Now the trusses themselves are going to be part of the tcdl. Top chord live load snow and other temporary loads top chord dead load roofing materials weight of the truss itself other permanent items attached to the roof bottom chord live load storage or living space and bottom chord dead load. Each piece of webbing where it contacts the sloped top chord acts like a support beam to the otherwise flimsy 2x4. 20 4 10 means that the truss was designed for 20 psf top chord live load tcll 4 psf top chord dead load tcdl 0 psf bottom chord live load bcll and 10 psf bottom chord dead load bcdl.

Factors that determine the size of the bottom chord include on center spacing dead loads. The bottom chord typically carries combined tension and bending stresses. Of fiberglass insulation at ceiling use 045 psf per inch 5 8 in. If the roof slope is steeper than 9 inches in 12 inches of run it doesn t take much width to end up with a nice room 12 feet wide with an 8 foot.

A determine the weights of the materials b identify the top chord and bottom chord dead load and live loads. The truss cords are made with high quality lumber 2x8 for the top cords and 2x12 for the bottom cords no lvl s involved. For traditionally spaced trusses the bottom chord is cut out of 2x4 or 2x6 dimension lumber but can also be cut out of 2x8 2x10 2x12 and even lvl material for roof trusses. In other words the truss design drawing should tell you what the truss was designed for.

Use hinge plates for piggyback trusses as opposed to building cap trusses. Trusses will have angled pieces of 2x4 that connect between the sloped top chord member and the horizontal bottom chord.