I am making some improvements to the kitchen in my century old farm house. One of my biggest pet peeves is the floor. It appears to have sunken down in the middle and is not soft but rather ‘springy’ when you bounce in the center of the room. I would like to correct this before moving on to more aesthetic undertakings. I appreciate any advice you may offer on this. Thanks
Thank you for the great question. This is such a common problem in prewar homes. Many times this is not an indication of a poorly built structure but rather a symptom of a home that was built with limited means conserving as much lumber as possible as having a less stout home was preferable to no home at all. But, prior to the second world war, there wasn’t necessarily a shortage of material, or money, it was strictly customary to frame floors and ceilings on 24 inch centers. With no intention of installing ceramic tiles on these floors, a little bounce was not an issue. But add to that a builders’ choice to use a 2x10, or even a 2x8 instead of a 2x12 then you have the makings of a pretty springy floor. Chances are it is not going to fall down any time soon, but if you want to stiffen it up for any reason there is an app for that.
What you’ll want to do is acquire yourself a beam. The beam can be made of many things. Steel I-beam, engineered wood, or traditional 2 by lumber in two or three plies nailed or screwed and glued together, or one solid milled piece of lumber. It will need to be the width of your room, perpendicular to the floor joists, plus a couple inches.
Now you have to get this piece of material into the basement, could be tricky if your room is 20 feet wide, and you have to manoeuver a 21 foot beam down a narrow old staircase. Maybe a basement window is a better idea.
Once down in the basement you need to decide how to support it. At either end you can use 4x4 posts cut nice and snug and driven in with a sledge hammer or on an outside foundation wall, a bracket fashioned from a chunk of 3 inch angle iron bolted to the concrete. If the floor is really bad, you may have to leave one end hang several inches low and use a jackpost to slowly work the beam up into place. It is also advisable to do this kind of coaxing when the weather is warm and humid as the old wood will be slightly more inclined to concede to your coaxing. If you have several inches you need to take up I would recommend doing this raising over the course of days or weeks instead of minutes or hours. Remember, it took 100 years to get into that position, it ain’t moving back in 20 minutes.
Once the beam is in its upright and locked position, you should plan to have a jackpost every 10 or 12 feet or in the center of the span at least.
Now remember that your floor will never be perfect. Chances are it wasn’t perfect when it was built. The best you can hope for is to stop the bounce, minimize the squeaks and make it so you don’t have to have one leg shorter than the other in order to enjoy your home.