Marion's Blog > Fixing Uneven Floors in an Old House: A Complete Guide

Fixing Uneven Floors in an Old House: A Complete Guide

Tuesday, April 08, 2025

Uneven floors are one of the most common issues in older homes throughout the Portland area. Whether you're living in a century-old Craftsman in Laurelhurst, a mid-century ranch in Lake Oswego, or a 1970s split-level in Beaverton, floor leveling challenges can affect homes of any age. Before proceeding with any new flooring installation, addressing these underlying issues is crucial for both aesthetic appeal and structural integrity.

Understanding why floors become uneven

Before tackling any floor leveling project, it's important to understand what causes floors to become uneven in the first place:

Foundation settlement

Over decades, foundations naturally settle into the soil beneath them. This settlement isn't always uniform, causing sections of the house to sit lower than others. Portland's varied soil conditions—from clay-heavy eastside neighborhoods to the more volcanic soils of the West Hills—can dramatically affect settlement patterns.

Structural issues

Sagging floor joists, damaged support beams, or compromised load-bearing walls can all contribute to uneven floors. In older homes throughout Oregon City and Wilsonville, these structural elements may have deteriorated due to age, moisture damage, or insect infestation.

Previous renovation work

Sometimes, uneven floors result from past remodeling projects where floors weren't properly leveled or where additions didn't properly match the height of existing floors. This is particularly common in homes in established neighborhoods like Sellwood or Irvington, which have undergone multiple renovations over many decades.

Moisture damage

The Pacific Northwest's famously wet climate can take its toll on homes. Prolonged moisture exposure can cause wood subfloors to warp, swell, or rot, creating uneven surfaces throughout the home.

Assessing the severity of the problem

Before deciding on a solution, you'll need to determine just how uneven your floors actually are:

Visual inspection

Start by examining your floors for obvious signs of unevenness:

• Do balls or toys roll to certain areas of the room?
• Are there visible dips or high spots?
• Do furniture pieces rock or wobble?
• Are there gaps between the floor and baseboards?

Measurement tools

For more precise assessment:

1. Use a long level (4-foot or longer) to check for sloping across different areas
2. Measure the difference in height at various points using a tape measure
3. Consider using a laser level for larger areas to identify the pattern of unevenness
4. String lines can help identify high and low spots across longer distances

Professional assessment

For significant unevenness or if you suspect serious structural issues, consider hiring a structural engineer to evaluate your home. This is particularly important for historic homes in neighborhoods like Ladd's Addition or Eastmoreland, where preservation considerations may come into play.

DIY solutions for minor unevenness

If your assessment reveals only slight unevenness (less than 3/8 inch difference over 10 feet), you might be able to address the issues yourself before moving forward with flooring installation:

Floor leveling compounds

For concrete subfloors or when preparing for tile installation:

1. Clean the subfloor thoroughly
2. Prime the surface if required by the leveling product
3. Mix self-leveling compound according to manufacturer instructions
4. Pour the mixture, allowing it to find its own level
5. Use a gauge rake to help distribute the compound evenly
6. Allow proper curing time before proceeding with flooring installation

Shimming techniques

For wood subfloors with minor unevenness:

1. Identify low spots using a straight edge or level
2. Use thin wooden shims between the subfloor and underlayment
3. Secure with construction adhesive and screws
4. Sand transitions between areas to create smooth slopes

Sanding high spots

In cases where there are isolated high spots:

1. Mark the high areas clearly
2. Use a belt sander with coarse-grit sandpaper for wood subfloors
3. Work gradually to avoid creating new low spots
4. Vacuum thoroughly after sanding

Professional solutions for major floor leveling

For more significant unevenness (greater than 3/8 inch over 10 feet) or structural issues, professional intervention is typically necessary before flooring installation:

Sister joists

When floor joists have sagged or weakened:

1. New joists are installed alongside existing ones
2. The new joists provide additional support
3. Gradually, they can help raise the floor to a more level position
4. This approach preserves original materials while adding strength

Beam replacement or reinforcement

For issues related to main support beams:

1. Temporary support walls are installed
2. The damaged or sagging beam is reinforced or replaced
3. New support posts may be added for additional stability
4. This addresses the root cause of many uneven floor issues

Foundation repairs

When foundation settlement is the primary cause:

1. Foundation specialists assess the situation
2. Techniques such as mudjacking, foam leveling, or pier installation may be employed
3. The foundation is stabilized and, where possible, raised to a more level position
4. This comprehensive approach addresses the source of floor unevenness

Complete subfloor replacement

In cases of severe damage:

1. Existing flooring and subfloor materials are removed
2. The floor framing is assessed and repaired as needed
3. New, level subfloor material is installed
4. This provides an ideal foundation for new flooring installation

Choosing appropriate flooring for uneven surfaces

Even after leveling efforts, some older homes may retain slight unevenness. Choosing the right flooring material can help accommodate these imperfections:

Forgiving flooring options

Some flooring types better conceal minor imperfections:

• Luxury vinyl plank (LVP) with thicker wear layers
• Engineered hardwood with adequate thickness
• Laminate flooring with integrated underlayment
• Carpet with thicker padding underneath

Flooring to avoid on slightly uneven surfaces

Some materials emphasize even the slightest subfloor irregularities:

• Large format ceramic or porcelain tiles
• Thin vinyl sheeting
• Solid hardwood planks wider than 5 inches
• Rigid flooring without flexible underlayment

The importance of professional flooring installation

Even with a properly leveled floor, professional flooring installation ensures the best results:

Expert assessment

Professional installers can:

• Identify any remaining leveling issues before installation begins
• Recommend appropriate underlayment or preparation techniques
• Ensure the subfloor meets proper moisture content requirements

Specialized equipment

Professionals have access to:

• Commercial-grade floor grinders
• Precision laser levels
• Moisture meters to detect potential issues
• Professional-grade installation tools

Installation techniques

Experienced installers know how to:

• Adjust installation patterns to minimize the visual impact of any slight unevenness
• Create proper expansion spaces for floating floors
• Ensure secure attachment for nail-down or glue-down applications
• Address transitions between rooms or flooring types

Maintaining level floors in the future

After addressing your uneven floors, take these steps to prevent future issues:

Regular inspections

• Check visible floor joists and beams annually for signs of sagging
• Monitor any cracks in walls or ceilings that could indicate ongoing settlement
• Watch for doors that begin to stick or hang unevenly

Moisture control

• Address any plumbing leaks immediately
• Ensure proper drainage away from your foundation
• Maintain adequate ventilation in crawl spaces and basements
• Consider a dehumidifier in particularly damp areas

Weight distribution

• Avoid concentrating extremely heavy items in one area
• Use furniture pads to distribute weight more evenly
• Consider the load-bearing capacity when placing heavy appliances or fixtures

Don't let uneven floors stand between you and your dream home—trust the Portland area's flooring specialists to provide expert solutions!

Marion's Carpet & Flooring Warehouses has extensive experience addressing uneven floors throughout Portland, Oregon City, Wilsonville, Beaverton, Lake Oswego, Tigard, Sherwood, Newberg, Hillsboro, OR, and Vancouver, WA. Our flooring installation experts can assess your unique situation and recommend the best approach for creating a beautiful, level foundation for your new floors. Visit our showrooms in Portland and Wilsonville, OR to discuss your project, or contact us today to schedule a professional consultation.