Chapter 10: Subfloor

2. Safety Issues

• Review the morning safety huddle talking papers associated with deck work.
• Care should be taken to avoid falls, either to the outside of the structure or into the basement. Stepping on the end of unsecured sheathing can be particularly dangerous as it can lead to falling into the basement. Care should also be taken around the opening for the stairs. Some crews choose to build a barricade around the opening. The opening should be securely covered at the end of the day to prevent falls from others who may climb onto the deck.
• Safety glasses and foam ear plugs should be worn when using power tools.
• Hardhats should be worn if working in the basement.
• A saw area with sawhorses and sheathing to form a table surface should be established outside the foundation in a low traffic area.
• Workers should be cautioned to work facing the leading edge of the deck.

3. Prior Tasks to Have Been Completed Before Starting

• Foundation poured and cured.
• Beam installed (if applicable).
• Ground backfilled around foundation if possible.
• Sill plate installed.
• All needed supplies ordered and on site.

4. Recommended Staff/Crew Assignments

• One person to be the safety supervisor.
• 3 people to be a saw crew. One will saw and the others will help support, stabilize, and transport material.
• A crew of 3 can put pencil or chalk lines on the sheathing.
• Two crews of 4 can install floor joists.
• Two crews of 4 can install rim board.
• One person can glue floor joists where sheathing will shortly be laid.
• A crew of 3 can place and drive sheathing in place.
• Once the subfloor is being installed, everyone (provided there is adequate room to safely work) who is not involved in another assignment will be called on to nail the sheathing to the floor joists.

5. Order/Tasks to be Completed
____Measure and mark location of floor joists on sill plate and 2 x 4 on steel beam or directly on LVL beam.
____Measure and cut floor joists to proper length.
____Install floor joists.
____Install joist hangers and headers for stair opening.
____Install rim boards.
____Cut and install joist blocking on all corners and the centers of the side walls.
____Glue top of floor joists.
____Install decking.
____Secure stair opening.
____Cleanup.

6. Tool Equipment list

• Circular saw
• Chalk box
• Pencils
• Hammers
• Sledge hammer
• Saw horses (2)
• Tape measures 25 ft and 50 ft
• Speed square
• Step ladders (2)
• 16 ft extension ladder
• Step ladder
• Eye protection and ear plugs
• Extension cord

7. Materials list

• Nails 16d, 10d, 8d
• Engineered floor joists
• Rim board
• Construction adhesive (Liquid Nails)
• Tongue in groove ¾ inch sheathing (OSB or plywood)
• Joist hangers
• Material for joist headers
• 2 x 4 for joist bracing

8. Quality Checkpoints
____Layout for floor joists accurate
____Floor joists installed in proper locations
____Rim board installed, floor joists are vertical before nailing
____Joist hangers and joist headers installed for stair opening
____Liquid Nails used prior to installing sheathing
____Sheathing applied properly, groove facing interior of house on first row.
____Sheathing extending beyond deck or stair opening cut off
____Sheathing nailed every 8 inches over each floor joist and 6 inches on the perimeter
____Stair opening covered and secured

9. Construction Drawings and Text
NOTE: The following drawings, diagrams, and text are to be used on the job site when a question arises as to methods and procedures associated with the task. The notes on the drawings have been geared toward use as a quick reference. If a more in-depth explanation is needed, please read the text description. But most importantly, consult your Habitat Site Supervisor and Construction Manager for advice as needed.

Floor Joists

• Mark the location of each floor joist. This is written as if the layout will start in the rear of the house, but check plans to determine where to start layout. It is also written assuming that joists are laid out 19.2" on center. Check the plans as this may vary. Each floor joist is 1 ½" wide. The center of the first will be 19.2" (most tape measures have a black diamond marker every 19.2") from the outside of the sill plate. Make a mark at this point and measure ¾" of an inch in both directions to locate the first floor joist. Move the end of the tape measure to the first joist marking and mark each 19.2" and 1 ½" beyond each of those marks. Using a speed square, draw lines at each mark to clearly locate each joist. If applicable, mark the 2 x 4 on the steel beam or directly on the LVL beam in the same manner. Locate the location of the stair opening and place marks for an additional floor joist on either side of the stair opening if called for on the plans. This will also need to be marked over the beam but not on the sill plate on the opposite side of the house. The plans may call for double floor joists and in this situation mark the location of both joists. After the marks are in place, use a speed square to make a line across the entire width of each board at the location of each mark.
• Measure the width of the rim board in from the outside of the sill plate on either side of the house and snap a chalk line. No marks are needed on the rear or front as a floor joist will be flush with the outside of the of the sill plate.
• Measure the distance between the chalk lines and cut engineered floor joists to length. Toenail with 10d nails (unless specified otherwise on plans or detail sheet) on both sides on both side sill plates and over center beam. Both ends of each floor joist should fall on the chalk line and the joist should be straight across the foundation. If applicable, the same sequence is used for the shorter joists used in the front of the house except that they will not cross the center beam.
• Stair opening framing is done as specified on the plans. Measure and make sure that the stair opening is the same as specified on the plans. Double joist hangers are often called for to support headers and are attached with 8d nails. Only nail the hanger on the side which will be on the inside of the stair opening. Measure the distance between the doubled floor joists and cut the header material to length. Two should be placed into each double joist hanger and then nailing the hangers with 8d nails can be completed. Single joist hangers are often used to attach floor joists to the headers.
• Cut rim board material to be installed between the floor joists and behind the rim board and nailed with 16d nails. 4 will be used at each corner and 4 will be installed between consecutive floor joists at the midpoint on either side as noted in blueprints.
• A long 2 x 4 may be temporarily nailed to the top of the floor joists in the center of the house to brace them until the sheathing is installed.

Rim board

• Rim board should be nailed to ends of all the floor joists. 10d nails should be used. Only 2 nails are necessary for each floor joist. Use a square to ensure that each floor joist is vertical prior to nailing. If this is not done, sheathing seams may not fall over the floor joists.
• Use the longest pieces of rim board available to ensure that the structure is not weakened by too many joints. When cuts are necessary, they should be made so that they fall on the center of a floor joist. Then nails can be driven into the floor joist from both sections of rim board.

Decking

• 3/4 inch plywood or OSB is applied in rows in the opposite direction of the joist layout. Sheathing is often started from the end of the house where the floor joist layout was started and typically on the opposite side from stair opening. The tongue side should face away from the house. This is very important because if it is not the tongues will be damaged when driving the sheets together and they will not fit properly.
• Apply construction adhesive on the floor joists where the first sheet of sheathing will be placed. Construction adhesive will be used for every piece of sheathing and gives added strength and reduces squeaking of floor.
• Place the sheet in place and nail with 8d nails every 6 inches on each floor joist. The end of the sheathing should fall over the middle of a floor joist so there is also room for the next sheet of sheathing to rest on the joist and be nailed to the joist. Continue the length of the house, always using full sheets. Pieces will need to be cut to size at the other end of the house and later around the stair opening
• The next row is begun from the same end of the house with a sheet that has been cut shorter than the starting sheet in the first row. The following row will be started with a full sheet. This staggering pattern will be continued and ensures that there are no continuous joints in the deck.
• Once the first piece on the second row is in place, place a scrap 2 x 4 across the floor joists in front of the sheet. Using a sledgehammer, hit the 2 x 4 until the tongue of the sheathing is driven completely into the groove of the previous sheet. This procedure will be continued with each new sheet of sheathing applied.

Stair Opening

• The stair opening can be temporarily covered. Additional material may be needed to provide strength so that temporary sheathing is safe to walk on.

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  Page last updated Saturday, May 3, 2008 at 6:39:52 PM