How to Level a Floor in an Old House

Man leveling wood floor

 

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Few aspects of a home elicit as much anxiety as a floor that out of level. When your floor slopes from one end to the other end or has dips and sags, it is a frustrating, vexing problem that is difficult to make right again. Before calling in a floor company or contractor to give you an estimate, determine which type of flooring problem you have.

Slanting/Sloping Floors vs. Sagging Floors

Not all floor problems are the same. One category describes floors that have a general, overall slant. The other category describes floors that might generally be level (from end to end) but within that span may have sags or dips.

Floors That Slant or Slope

Floor slopes and slants are common in old houses. A slant/slope situation might be one where, over the course of 15 or 20 horizontal feet, the floor slopes down one or two inches. Except for that slope, the floor itself might be flat. For rooms that have a general slope, the issue may be foundation problems that require the assistance of a foundation repair company or a general contractor.

Floors That Sag or Dip

Different from slanting/sloping floors are those that sag or have dips. For instance, you may have a dining room floor that, end to end is level, but between those two points are various sags and dips. Your foundation may not be the problem. Instead, it may be an issue with joists and beams below your floor that require shoring up. In some cases, pouring floor leveling compound will fix the problem.

Safety Considerations

Floor leveling (other than pouring self-leveling underlayment) is a major project that can permanently alter your home. Be careful when taking on any of these projects by always having an assistant help you. Also, be sure to wear eye protection.

Project Metrics

  • Working Time: From 1 day to several weeks
  • Skill Level: From Beginner to Expert
  • Material Cost: $100 for self-leveling underlayment, on up to $15,000 or more for major foundation repair

What You Will Need

Equipment/Tools

Materials

  • Self-leveling underlayment (floor leveling compound)
  • Two-by-sixes or two-by-eights for sistering floor joists
  • Bolts, nuts, and washers

Instructions

Fixing a Floor That Slopes or Slants

  1. If the floor itself is flat, the foundation footer may have subsided or sunk. With foundation problems, this is an identifiable problem and there are companies that specialize in foundation repair. They will jack up that portion of the house and place new footers. Anything involving 20-ton house jacks will take time; you cannot jack up a house in one day. It has to be jacked up slowly over days or even weeks to avoid cracking drywall, plaster, windows, and even structural elements.
  2. The sill (the wooden part of the house that rests on the foundation footer) may have deteriorated either due to rot, water, termites, or carpenter ants.
  3. Interior floor repairs will not fix end-to-end house slopes. You will need to jack up the house and re-level it or stabilize it and live with it as-is.

Fixing a Floor That Sags and Dips

  1. Small, localized dips and sags are easily fixed by pouring self-leveling underlayment in the problem area. Compound can correct sags and dips as deep as 1 1/2 inches.
  2. If you have access to the basement or crawlspace, it is possible to jack up saggy joists until they are level and then sister them so that they remain straight after the jacks are removed. Sistering is the process of mating up two boards with bolts, nuts, and washers so that the new board corrects or supports the other, weaker one.
  3. Place adjustable steel columns under the joists to keep them propped up. This steel column fix does require that the base of the column be secured to the basement floor and the top of the column be secured to the joist.
  4. On the top side of the floor, another fix-it idea to lay down new hardwood over the existing floor. A plywood subfloor will bridge any minor waves in the existing floor, and leveling compound would help, too. You will have to make sure your joists can handle the addition of considerably more weight from the plywood subfloor and any floor coverings. Below, you can sister the joists and add a few adjustable columns to strengthen the joists to handle the additional weight.

Some homeowners, when confronted with staggering bills for floor repairs, come to terms with their floors. Old houses often have floors that are less than perfect; even historic houses have saggy, sloping floors. Minor workarounds are possible, such as leveling individual elements within the floor (tables, armoires, cabinets, etc.). 

When to Call a Professional

Few floor specialists deal only with this type of problem. The best route is to contact a general contractor. For foundation repairs, contact a foundation repair specialist.