These rafter spans are for #2 lumber, a ground snow load of 30 psf, the ceiling not attached to rafters, and a dead load of 10 psf. All other data can be found in the 2012 International Residential Code Rafter Spans. Be sure to use rafter clips on every rafter not nailed into a ceiling joist. Nail on a three foot collar tie every four foot to meet code requirements. Use two 12d toe nails one one side and and one on the other to firmly attach the rafter.

Download a  free PDF version of the entire text for the 2012 International Residential Code. Read with Acrobat or Phantom with searchable text.

Controlling moisture in the crawl space underneath a house is important to prevent structural damage caused by rot and the development of dangerous molds. Proper planning on new home construction or careful analysis on existing homes will prove invaluable.

Moisture in Crawl Spaces

Moisture makes its way into crawl spaces primarily by two means. During heavy rains and melt-offs, the water table can rise higher than the footing. This problem literally leaks from within and can only be prevented with a perforated pipe or french drain positioned lower than the footing. The water can drain away from the crawl space by gravity or it may have to be pumped away if there is not sufficient room to “find daylight”. This type of drain is required by the 2012 International Residential Code on virtually all new home construction where the foundation holds back earth in all but desert climates.

While this type of drain is more difficult to install on an existing home, it is often the only way to be sure the crawl space will stay dry. On many homes this means doing the excavation manually. This is a great deal of digging with hand tools and much of the soil will also need to be completely taken away to make room for the gravel. Excavation contractors are generally not equipped with the right personnel to handle such projects, so check with your local building contractors.

Preventing Moisture In a Crawl Space from Water Run-Off

When it rains, the shape and grade of the landscape direct the flow of water. It never needs to be flowing toward the house; always away from or around it. There is no way to prevent the earth from becoming saturated with water, so wherever the foundation holds back earth, it should have an approved waterproofing applied to the outside surface of the blocks from the top of the footing to the finished grade. These flexible sealants provide a higher level of protection against positive pressure from water.

Controlling Condensation in Crawl Spaces

Condensation can be a particularly damaging problem if there is not proper ventilation in the crawl space. The 2012 International Building Codes requires one vent within 3′ of each corner. Power vents are an optional replacement for the traditional ones. The code also requires an access of at least 16″ x 24″  when through the perimeter of the foundation, but must be 18″ x 24″ when the access door is in the floor of the house.

We recommend using all of the above methods for moisture control in conjunction with each other. A home is a big investment whether it is a new one or not. Water damage from underneath is something that is almost always preventable.

Means of Egress

Means of egress is basically an escape route from a dwelling in the event of a fire or other catastrophe according to most building codes. These general guidelines are based in the 2012 IRC.

Door Egress

There should be a clear path from everywhere in the dwelling to a door without going through a garage. There has to be at least one door at least 32″ wide. This is a small size for an entry door. Just know that it can be very difficult to get furniture through a door this small. It is best to have a front door and a back door. They really should be 36″ wide.

It has to have a floor or landing on each side of it that drops down no more than 1 1/2″ from the top of the threshold. If their is a landing on the outside, then it can drop no more than 7 3/4″ as long as the door does not swing out over it. Hallways, stairs, and bedrooms also have to meet specific criteria.

Window Egress

In order for a window to be compliant in residential applications, it must meet the following criteria to provide an adequate means of escape from a bedroom, basement, or a habitable attic that does not have an exterior door in the event of a fire or other emergency. The most popular size for first floor bedrooms is a 2’8″ 5’2″ double hung window. For applications where the sill is more than 44″ above the finished grade, the best choices for double hung units are 3’0″ 5’2″ and 2’8″ 6’0″.

• 44″ Max sill height off the floor
• 5.7 Square feet minimum clear opening for second floor and up
• 5  Square feet minimum clear opening for first floor (Sill must be within 44″ of finish grade)
• 20″ Minimum clear opening width
• 24″ Minimum clear opening height

Other Considerations

• All stairs and hallways have to be a minimum of 36″ wide.
• Stair risers can not exceed 7 3/4″.
• Tread runs can not drop below 10″ so long as there is a one inch overhang.
• There must be a continuous graspable handrail down any flight of stairs.
• It should be between 34″ – 38″ high and project no further than 4 1/2″ into the stairway.

For more detailed specifications follow this link to page 88 of the International Residential Code.

Maintain a Practical Means of Egress

Even after inspection, it is important to maintain proper egress for any bedroom. It is important for the occupant to be able to escape from fire or other catastrophe in a hurry.

• Do not permanently shut an egress window or door with nails, screws, glue, or anything else.
• Do not block the window or door with a piece of furniture or anything else.
• Do not change the grade level on the outside making it too far to jump.
• Do not cover the outside with a storm window or cover it with plywood even if it is broken.
• Do not paint the window or door shut!
• Do not use stairways or hallways for storage

The floor Joist span chart and building code requirements are based on data from the 2012 International Residential Code using number 2 lumber.

Types of Floor Joists

Joists for use in residential framing applications fall into two different categories; tree sawed and engineered. This page focuses on the tree sawed variety. Kiln dried number 2 Pine is the most widely used material. It is relatively inexpensive and is widely available. It is available in sizes that will work for joists from 2 x 8 x 8′ to 2 x 12 x 24′. There are limits on how far these boards can span. 

Floor Joist Span Chart for 40 lb Live Load

Floor Joist Span Chart for 30 lb Live Load 

Floor Joist Building Code Requirements

The best way for a joist to transfer its load is for it to stack. This simply means for it to rest directly on top of another framing member like a drop girder, a wall, or a pressure treated mud sill. There is some criteria the joists must meet according o the 2012 International Residential Building Codes.

• The joist must have a minimum of 1 1/2″ riding on the wall or beam.
• If the joists are lapped, then they must be lapped at least 3″.
• Maximum end notches for 2 x 8, 2 x 10, and 2 x 12 respectively are 1 13/16″, 2 5/16″, and 2 13/16″.
• Use an approved hanger or a 2 x 2 ledger strip on flush beams for spans greater than 12′.
• When framing openings, use header and trimmer joists. Double any header over 4′ and any trimmer joists with a header attached within 3′ of its bearing.
• Use a minimum of 3 8d nails for toe nailing to girder or sill.
• Use a minimum of 3 10d nails for face nailing and lap joints.

Be aware that these spans and code requirements are taking things to the absolute limit. In a practical application it is a good rule of thumb to not use 2 x 8’s at all, never span a 2 x 10 over 14′, never span a 2  x 12  over 20′, and use as many nails as possible without damaging the wood.