On longer spans the beam may require much more bearing space as indicated by this table.
Attic beam measurement.
We have learned from our experience to use at least a 3 1.
A two 2 by 6 standard beam has actual dimensions of 1 5 by 5 5 inches which would give a section modulus of 1 5 x 5 5 x 5 5 6 7 6 which is not enough for this example.
The beam system we show will work for nearly any opening up to 12 ft.
Precise measurement is the most difficult as you need to consider all underlying obstructions carefully before proceeding with your plans.
Joists and rafters must be strong enough not to break when loaded.
Cut a length of rope equal to this final measurement.
A pair of rafters is called a couple.
Strength of a material is obviously important.
Unlike stiffness live loads and dead loads are added together to determine minimum design values for strength.
Tie a knot in one end to prevent it from accidentally slipping out of the pulley.
Back up to the pulley on the attic.
Well assuming the attic eats 6db that statement is wrong.
Bedrooms and habitable attic floors l 360 30 psf.
When cutting your beam pocket add 1 2 to the steel beam width measurement to allow for an easier installation.
Step 4 run the rope through the pulley.
Staggered pattern with at least a 3 x 120 nail.
Use of joists in attic flooring.
The 2012 irc code calls for a minimum of a 32 o c.
Attic floors with limited storage l 240 10 psf.
We used a bosch green line laser to connect both beam pocket locations and then used a speed square to mark cut lines directly on the joists.
There could be many rafters supporting a roof.
The formula for the section modulus is beam width times beam depth squared divided by 6.
You can sister the joists by cutting 2 x8 boards the same length as the joists applying construction adhesive and affixing each to a joist with nails.
Fortunately this is a fairly easy fix.
A 2 by 8 beam would be sufficient.
To start each cut a circular saw was used and finished up with a reciprocating saw.
The subfloor installation is easy.
You might open up your attic and find bare joists with fiberglass or cellulose insulation between the joists.
Any lumberyard will be able to furnish the beam and other materials.
Our 12 ft long beam was made from doubled 11 7 8 in wide x 1 3 4 in thick lvls laminated veneer lumber a very common strong type of beam that looks exactly like thick plywood boards.
Rafter is a sloping beam usually wood that supports a pitched roof.
A 1 4 wave would be 0 dbd at best probably worse but a 6 element beam would be 8 dbd so it looks like the attic beam antenna would win by about 2db assuming same height above ground.
Beams of more than one ply must be fastened together with either nails or bolts.
Step 3 screw an eye hook into the beam where you made the mark.
Attach a pulley to it by sliding the pulley s hook into the eye.
