Floor System Notes

Theory:

1.      Discuss Concrete Foundations and their make-up

A.     Show a picture of a footing Picture #1

                                                                           i.      Discuss the process of digging a footing and pouring a footing

B.     Show a picture of a foundation Picture #2.

                                                                           i.      Discuss the process and need for laying a block foundation

C.     Show a picture of a slab form Picture #3 & 4

                                                                           i.      Explain the process of constructing a slab foundation

2.      Floor Systems – Explain what a crawl space is and show picture of a crawlspace

3.      Discuss the parts of a floor system and explain what their purpose

A.     Mud Sill – A treated board that is installed between the header joist and the foundation wall.  The mudsill is attached to the foundation with anchor bolts and the header is attached to the mud sill with 16d common nails.  Show Picture #5

B.     Anchor Bolts – a J shaped bolt that is used to attach the mudsill to the foundation.  This bolt also anchors the house to the foundation.  Building code requires that anchor bolts be spaced a maximum of  6’ apart and be no further than 12” from the end of any plate. Show Picture #5 & 6

C.     Header – An upright framing member that runs around the perimeter of the building, common joists are attached to using 16 common nails. Show Picture 7,8,9

D.     Common Joist – A series of framing members that make up the body of the floor frame  Show Picture 7

E.      Double Joist – Two common joists that are nailed together carry extra heavy loads.  Double Joists should be installed under all interior walls that run parallel with the common joists.  Double Joists should also be installed in places where there will be heavy loads when the house is complete such as large bathtubs or pool tables. Show Picture 7

F.      Rough Opening – An opening in a floor system for stairs or chimneys.  Information concerning the locations of these rough opening can be found on the Floor Plan. – Show Picture 10

G.     Trimmer Joist – A full length joist that is used to construct a rough opening in a floor.  This rough opening could be for something like a set of stairs. Show Picture 11

H.     Tail Joist – a short joist that runs from the outside header to the header that makes up a rough opening. Show Picture 11

I.        Joist hanger – A metal stirrup that is used to attach a joist to a beam. Show Picture 12

J.       ¾” Tounge and Groove OSB Subfloor – This is a 4’X8’ sheet of OSB(Oriented Strand Board) that is nailed to the floor system and serves as a walking surface.  One side of the panel has a tongue on it and one side has a groove on it.  This tongue and groove system serves to interlock the panels together and minimize deflection of the subfloor.  Finished flooring (Carpet, tile etc.) is installed to this.  This type of sub floor must be glued and nailed.  There are two types Normal OSB and Top Notch.  Top Notch is waterproof and Normal OSB is not.  When Normal OSB gets wet it can swell and cause major problems. Show Picture 13,14

K.    Bridging or Bridge Blocking – A block that is nailed between the joists to prevent unequal deflection of the joists.  According to Building Code, bridging must be installed between joists at intervals of not more than 8’. - Show Picture 16

L.      Wood I beams – A type of manufactured joist that consists of an OSB strip bonded between two boards that have groves in them.  This type of joists has a much greater span than normal joists.  The OSB strip can be cut to allow wires and plumbing to pass through the joists but they can only be cut according to manufacturers instructions.  The top and bottom boards should never be cut. Show Picture 16

M.   Floor Trusses – These types of joists are engineered to carry the load that they will be carrying.  They are made by using nail plates to hold the parts together.  No part of these types of joists can be cut without the permission of the engineer that designed them. Show Picture 17

4.      Select the proper girder, beam size and joist size according to specific floor load and span data.

1.      The first step in selecting the joist size is to determine the live load and find the correct table in the code book. This can normally be found on the blueprints.  In this example we will use a 40 PSF live load. (Live load is the weight of all moveable loads that are in a building).

2.      The second step is to determine the Dead load that the floor system will be carrying and find the correct table in the Code Book.  This is normally found on the blueprints. (Dead Load is the weight of  the building materials used to construct the building)

3.      The third step is to determine the type of lumber that you are using to construct the building.  Normally this will be Southern Pine #2.

The fourth step is to identify the size of lumber that will span the distance that you need to span.  If there is no lumber that will span the distance that you need the spacing of the joists may need to be decreased.