How to Level a Floor in an Old House

leveling a floor in an old house

The Spruce / Sarah Crowley

Project Overview
  • Total Time: 1 day - 1 wk
  • Skill Level: Intermediate
  • Estimated Cost: $100 to $15,000

Few aspects of a home elicit as much anxiety as a floor that is out of level. When your floor slopes from one end to the other, 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 and decide if you might be able to handle the problem yourself.

Slanting/Sloping Floors vs. Sagging Floors

Not all floor problems are the same. One category applies to floors that have a general, overall slant. The other applies to floors that might be generally level (from end to end) but might have sags or dips only in certain places.

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 15–20 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 is level end-to-end, 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 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.

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What You'll Need

Equipment / Tools

  • Laser level
  • Electric miter saw
  • Rotary level
  • Framing hammer
  • Tape measure
  • Bubble level
  • Carpenter's pencil
  • Adjustable steel columns
  • Cordless drill
  • Auger bits
  • House jacks


  • Self-leveling underlayment (floor leveling compound)
  • 2-by-6s or 2-by-8s for sistering floor joists
  • Bolts, nuts, and washers


Fixing a Floor That Slopes or Slants

If the floor itself is flat, the foundation footer may have subsided or sunk. Alternatively, 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. Both of these are identifiable problems and there are companies that specialize in foundation repair. However, if you are an advanced DIYer, you can attempt to tackle the project yourself.

  1. Place New Footers

    Jack up the portion of the house that is sinking 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. Remove the Jack

    After some time has passed, take off the jack and re-level it or stabilize it.

Fixing a Floor That Sags and Dips

There are multiple ways to fix a floor that sags and dips.

  1. Pour Self-Leveling Underlayment

    Pour self-leveling underlayment in the problem area. The compound can correct sags and dips as deep as 1 1/2 inches.

  2. Sister the Joists

    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. Prop Up the Joists

    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. Lay Down New Hardwood

    On the top side of the floor, another fix-it idea is 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.