Construction Topics - Floor Joist

Floor joists are fundamentally the lateral support of the building structure. In the case of inter city row homes, particularly as in Philadelphia these old members were solid one piece timbers measuring approximately 3" wide x 91/2"deep. The span, which is the distance measured end to end varies depending on the distance between the buildings party walls. When assessing floor joist replacement, a professional engineer should always be consulted. No floor joist should be removed without a professional engineers advise. I have seen several conditions where a vital floor joist was removed and floors sloped or sagged, walls cracked and trim has pulled any from the walls or the entire house settled.


If you think you need professional help here are some things to look for. Do the joist twist at either end? Do the joist drop down on either end and appear to be crushing the material under it? Do the joist sag in the middle? Do you see cracks in the joist along the span? Does the joist have a post propped up under it? Does the joist show signs of flaking and deteriorating ?


The average building measuring approximately 60 foot deep from front to rear takes about 45 - 50 joists per floor. There are a number of lumber of yards that carry the true size of old joist timber for an exact width and depth replacement. Although smaller joist can be sistered (nailed) together to achieve the proper width, the extra time and labor cost in assembly can affect the budget. I personally don't like the method.


Remember always consult a professional.