Leveling a deck is essential for safety, water drainage, and longevity. This practical guide explains how to assess the deck, choose the right methods, and perform steps to achieve a solid, level surface. By following a structured approach, homeowners can address uneven joists, uneven posts, and sinking supports while avoiding common errors. The focus is on clear, actionable steps and common tools used in typical residential decks.
Assessing The Deck And Planning
Begin with a thorough inspection to identify how much the deck leans and where the trouble spots lie. Use a long carpenter’s level, a straightedge, and a string line to gauge level across multiple points along the railing line and the edges of the deck. Check for movement in posts, sill boards, and footings. Document measurements and note whether the deck tilts toward the house, away from the house, or has localized dips. A written plan helps determine whether to shim, replace posts, or reset footings.
Environmental factors influence leveling work. Soil settlement, frost heave, poor drainage, and age all affect deck stability. Plan to address drainage issues by ensuring deck boards slope slightly away from the house and that gutters and downspouts direct rainwater away from footings. If the deck shows widespread wobble or structural failures, the project may require professional structural assessment.
Tools And Materials You’ll Need
Gather these essentials before starting:
- Long level (4–6 feet) and a shorter torpedo level
- Measuring tape and straightedge
- Chalk line or laser level
- Jack stands or hydraulic bottle jack (for temporary lifting)
- Wood shims, compatible with deck framing (plaqued or plastic shims)
- Concrete deck posts or post anchors (if needed)
- Grout or masonry mix (for stabilizing footings, if applicable)
- Carpenter’s saw, pry bar, and fasteners
- Post sleeve or beam pocket inserts (optional)
- Protective gear: gloves, eye protection, hearing protection
For safety, never perform leveling with the deck loaded with people or heavy furniture. If lifting is required, do so gradually and support the load to prevent joists from bending or snapping.
Leveling Methods Overview
There are several approaches to level a deck, depending on the condition and accessibility of the support structure:
- Shimming existing posts or beams to correct minor level discrepancies
- Raising sunken footings by adjusting post heights with washers, shims, or post caps
- Replacing or resetting posts and footings for major settling
- Rebuilding sections of the deck where joists or ledger connections are compromised
Start with the least invasive method—shim and adjust—before moving to more involved options like footing replacement. Safety and code compliance should guide decisions, especially in areas with frost cycles or seismic activity.
Step-By-Step: Shimming And Raising Posts
Step 1: Secure The Area. Clear the deck surface and have a helper hold the level in place while you inspect. Step 2: Mark High Or Low Points. Use a chalk line across multiple joists to identify the lean direction and measure gaps with a tape measure. Step 3: Prepare Shims. Use durable plastic or hardwood shims cut to fit the gap between the post base and the beam or concrete pad. Step 4: Insert Shims. Slide shims in increments to equalize the deck height. Avoid overtightening; shims should sit flat and evenly under the post base. Step 5: Check For Level. Re-check across several points with the level and adjust as needed. Step 6: Stabilize. Once level is achieved, secure with added fasteners or post-notching to prevent movement.
Step 7: Recheck Drainage. Inspect deck slope to ensure water flows away from the house. Step 8: Finish Edges. If shims create exposed gaps, trim or cap to maintain aesthetic and safety. This method is suitable for minor to moderate settling and can restore level without replacing components.
When To Stop And Consider Alternatives
If the deck wobbles after shimming or posts show signs of ongoing movement, the problem may be structural. In such cases, consider resetting footings or replacing compromised posts and anchors. Major settlement often indicates soil issues or frost heave, which may require professional assessment and possible foundation work.
Raising Or Replacing Footings
Step 1: Determine Footing Status. If footings are cracked, shifted, or insufficiently deep, they may need replacement or lifting. Step 2: Temporary Support. Use jack stands or a hydraulic jack to support the deck while footing work is performed. Step 3: Lift And Align. Gently lift the deck to the desired height, using shims to fine-tune. Step 4: Install New Footings. Excavate around existing footings if necessary, install deeper or larger footings, and set with concrete. Step 5: Reconnect Posts. Secure posts to new or adjusted footings and re-check level across multiple points. Step 6: Cure And Inspect. Allow concrete to cure per manufacturer recommendations and verify stability.
Raising footings can restore height and level but requires careful measurement and adherence to local code requirements for footings and frost protection. It is often more durable than incremental shimming in cases of significant settlement.
Rebuilding Sections: When It Isn’t Leveling Anymore
In some cases, a deck is fundamentally out of level due to deteriorated framing or age. If joists are warped, ledger connections are loose, or posts are compromised, partial or full rebuild may be necessary. Steps include: replacing corroded or damaged joists, reinforcing the ledger board with proper lag screws or through-bolts, and rebuilding affected sections on solid, well-drained gravel or compacted soil. This approach ensures long-term stability and reduces future maintenance.
Note: Any rebuild should comply with local building codes and include proper flashing and ledger protection to prevent water intrusion and decay. Consulting a structural engineer or experienced contractor is advisable for extensive projects.
Common Mistakes And How To Avoid Them
The following pitfalls can undermine deck leveling efforts:
- Over-shimming or under-shimming causing uneven surfaces or post instability
- Ignoring drainage which leads to pooling and wood rot
- Using inappropriate shim materials that deform under load
- Not rechecking level after finishing adjustments
- Failing to secure re-stabilized posts, risking movement
To avoid these, measure frequently, use appropriate materials, and always recheck level after any adjustment. Document readings to track progress and provide a reference for future maintenance.
Maintenance And Long-Term Care
Regular inspection every six to twelve months helps catch shifts before they become major problems. Look for cracks in concrete footings, cracked or split boards, and loose fasteners. Clean gutters and ensure downspouts direct water away from the deck. Apply protective sealant to prevent water ingress and monitor seasonal soil movement in frost-prone regions. Addressing small problems promptly preserves the deck’s level, safety, and lifespan.
Additionally, consider installing proper ventilation beneath the deck to reduce moisture buildup, which can contribute to wood rot and frame instability. A properly graded surface with adequate airflow extends the life of decking materials and supports a stable, level structure over time.
Frequently Asked Questions
Q: Can I level a deck myself, or should I hire a pro? A: Minor leveling can often be done by a confident DIYer with the right tools. For major issues, structural concerns, or frost-prone sites, hiring a licensed contractor is advisable.
Q: How do I know if the deck needs post replacement? A: If posts show extensive movement, cracks, rot, or shifting after leveling attempts, post replacement is likely required for lasting stability.
Q: What about building codes? A: Local building codes govern deck leveling, footing depth, and post connections. Always check with the local building department before beginning work to ensure compliance and safety.