How do you strengthen stairs from underneath?

Strengthening stairs from underneath can be an effective way to reinforce and stabilize existing steps without having to completely replace them. There are several methods that can be used to strengthen and support stairs from below, depending on the type of staircase and the issues that need to be addressed.

Assessing the Current Staircase

Before undertaking any staircase reinforcement project, it’s important to thoroughly assess the current condition of the stairs. Look for any sagging, creaking, or cracking in the steps or staircase structure. Try jumping or stomping on the stairs to detect any weaknesses or flexing. Check underneath the staircase and look for any broken, cracked, or deteriorating stringers, risers, and other structural supports. Identify the materials the staircase is constructed from as well – wood, concrete, steel, etc. Understanding the current weaknesses and materials will inform the best method for strengthening from underneath.

Refurbishing Wooden Staircase Framing

For wooden stairs, focus on reinforcing the framing and substructure. The stringers or side boards that support the steps and risers can often be weakened from age, excessive use, or insect damage. Refurbishing rotten or deteriorating stringers is often the key to reinforcing wobbly wooden stairs.

Start by completely removing any broken, damaged, or rotten boards. Measure and cut new lumber to size to replace stringers or risers. Sister the new boards next to the old, attaching them using construction adhesive and screws staggered every 4-6 inches. For additional strength, also screw solid blocking between stringers every 3-5 steps.

You can also add triangular knee braces for more support. Cut braces to size and screw into place underneath tread landing areas where legs meet stringers. Wood glue will help braces adhere tightly.

Concrete Staircase Reinforcement

Unlike wood stairs, concrete stairs are reinforced with metal rebar hidden within the concrete. Over time, corrosion can compromise these internal reinforcing bars and weaken the concrete, causing cracking, crumbling, and collapse. Rather than replacing the entire concrete staircase, underlying support can often be added.

For concrete steps that are still relatively intact, add bracing underneath by adhering steel support beams or angled metal brackets with concrete adhesive. If cracking and deterioration is more extensive, the damaged sections of concrete will need to be removed and replaced fully. Cut away broken chunks and rebuild stairs using forms and new poured concrete reinforced with additional rebar.

Bolstering Winder Stairs

Winder stairs have triangular steps radiating around a curved or spiral central pole. Their curved nature means they undergo unique rotational forces and require specialized reinforcement techniques.

Augment under-tread support by sistering new stringers to the outer and inner curves of the winder staircase. Then improve lateral stability by adding substantial blocking between stringers every few steps around the central newel post. You can also utilize heavy-duty steel brackets anchored into the foundation underneath winder landings.

Adding Returns and Wall Anchors

Inclined stairs require strong vertical supports on both ends. Returns are L-shaped walls perpendicular to sloped staircases. When properly constructed, they prevent side-to-side swaying and absorb downward forces from above. Refurbishing damaged returns or adding new ones provides major strengthening benefits.

Returns should be well-integrated with the rest of the home’s structure. Use anchor bolts to securely connect returns into the building’s framing and foundation. Installing additional support beams on either side of the returns will further boost structural integrity.

You can also anchor the staircase into surrounding walls for added stability. Using long lag screws or bolts, connect the stringers or risers directly into the studs or masonry walls the stairs are located between.

Using Steel Jacks for Added Support

For straightforward additional support, adjustable steel jacks can be positioned underneath stairs where needed. Placed under tread landings or other vulnerable spots, hydraulic jacks can bear some of the staircase’s weight and prevent sagging or failure.

Come-along winches can provide a similar effect by using braided steel cable. Anchoring the winch into a secure floor joist or wall stud and ratcheting the cable tight underneath the stairs creates an uplifting support force.

Improving Foundations for Reinforced Stairs

In some cases, the underlying groundwork and foundations holding up a staircase may require improvements as well. Stairs that are pulling away from the building or sinking on one side likely have an issue with poor foundations.

For concrete pad foundations, inject expanding polyurethane foam underneath to gently lift and stabilize stairs. Or, pour a fresh concrete footing reinforced with rebar if the old one has become cracked and compromised.

If the stairs sit on adjustable pier blocks, you may just need to shore them up. Stack additional solid concrete blocks underneath to boost support and get the stairs back to the proper height.

When to Call a Professional

Reinforcing simpler wooden or concrete stairs as a DIY project can potentially save money. But more complex staircase repairs are often best left to experienced contractors. Spiral and winder stairs, curved designs, and monumental or architecturally ornate styles may require engineering expertise.

Some indicators that professional staircase repair is the wise choice include:

• Significant visible damage or deterioration
• Persistent and pronounced wobbling or shaking
• Partially collapsed or broken steps
• Cracks wider than 1/4 inch
• Excessive previous makeshift repairs
• Legal multifamily rental property stairs
• Stairs with extensive ornamental details

A licensed and insured staircase contractor will have the knowledge and skills to properly diagnose underlying structural issues and prescribe appropriate repairs. They will also be able to pull required permits and ensure staircase modifications meet local building codes.

Safety Precautions

It’s important to exercise caution whenever undertaking staircase reinforcement projects:

• Prevent others from using the stairs while work is in progress
• Use barriers and signage to block off the area below stairs
• Wear protective gear like gloves, goggles, hard hat, and dust mask
• Work slowly with a partner for safety
• Keep the area clear and tidy to avoid trips and falls

Rushed or slipshod staircase repairs can do more harm than good. Take the time to thoroughly assess the issues and reinforce the stairs using proven methods and quality materials.

Inspection and Maintenance

Periodically inspecting and maintaining stairs is key to getting years of safe use from them after repairs:

• Visually check for new cracks or deterioration every 6 months
• Tighten any loose bolts, screws or anchors
• Sand and repaint exposed wood to prevent moisture damage
• Reseal concrete and masonry to avoid cracks from water
• Lubricate stair lifts and chair lifts regularly per manufacturer
• Ensure lighting is adequate and operational
• Replace worn carpet, wood, or nosings when needed

Proper underlying structural support combined with diligent upkeep will help reinforced stairs remain defect-free and able to safely handle daily use.

Conclusion

Reinforcing and stabilizing stairs from underneath is an efficient process that can restore strength and remove wobble without having to completely rebuild staircases. After thoroughly assessing for deficiencies, methods like sistering new stringers, adding returns, installing jacks and braces, and improving foundations can bolster stairs without major construction. However, some complex stairs will require professional engineering expertise. With the proper repairs and ongoing maintenance, reinforced stairs can once again become solidly grounded assets providing safe passage within a building for years to come.