Under Deck Post Hole Digging: Expert Guide

Digging a post hole under an existing deck can be a daunting task, but with the right tools and techniques, it's achievable. This guide will walk you through the process, ensuring your new post is secure and your deck remains stable.

Before you begin, ensure you're familiar with your deck's structure and the layout of any utilities beneath. Always call your local utility locating service to mark any underground lines before digging.

Preparation and Planning

Proper preparation is key to a successful post hole dig. Here's what you'll need to do before you start:

1. **Gather Your Tools**: You'll need a post hole digger, a tape measure, a level, a shovel, a saw (if your post needs cutting), gloves, safety glasses, and ear protection. If your soil is rocky, you might also need a pickaxe.

Measuring and Marking

Accurate measurement is crucial to ensure your new post is perfectly aligned with your existing deck. Here's how to do it:

1. **Find the Center**: Measure the width of your deck and mark the center point on the underside.

2. **Determine Post Depth**: Measure from this center point down to the ground. This is the depth you'll need to dig your hole. Typically, the post should be at least one-third of its above-ground height below the surface.

Locating Underground Utilities

Before you start digging, you must locate and mark any underground utilities. Here's how:

1. **Contact Your Local Utility Company**: Call your local utility locating service. They'll mark the approximate locations of underground lines with flags, paint, or both.

2. **Respect the Marks**: These marks indicate the approximate locations of underground lines. Stay at least 18 inches away from these marks when digging to avoid damaging any lines.

Digging the Post Hole

Now that you're prepared, it's time to start digging. Here's how to do it safely and effectively:

1. **Start Digging**: Using your post hole digger, start digging at the marked spot. If the soil is hard, use a pickaxe to break it up first.

Digging to the Correct Depth

It's crucial to dig to the correct depth to ensure your post is stable. Here's how to do it:

1. **Measure as You Go**: Regularly measure the depth of your hole using your tape measure. Stop digging once you've reached the required depth.

Widening the Hole

Once you've reached the correct depth, you'll need to widen the hole to accommodate the post. Here's how:

1. **Use a Shovel**: Switch to a shovel to widen the hole. You'll need to create a hole that's roughly twice as wide as your post to allow for concrete.

Setting the Post and Pouring Concrete

With your hole dug, it's time to set your post and secure it with concrete. Here's how:

1. **Set the Post**: Place your post in the hole, ensuring it's perfectly vertical using your level. You might need to temporarily brace the post to keep it in place.

Mixing and Pouring Concrete

Concrete is essential for securing your post and preventing it from rotting. Here's how to mix and pour it:

1. **Mix the Concrete**: Follow the instructions on your concrete mix to create a mixture that's neither too wet nor too dry.

2. **Pour the Concrete**: Slowly pour the concrete into the hole around the post, using a trowel to pack it in and remove any air pockets. Leave a few inches of space at the top of the hole for water drainage.

Allowing the Concrete to Set

Concrete needs time to set and harden. Here's how to ensure it does:

1. **Keep it Moist**: Cover the concrete with a plastic sheet to keep it moist. This helps the concrete to set properly.

2. **Wait**: Allow the concrete to set for at least 72 hours before removing any temporary bracing or using the post.

And there you have it! With these steps, you've successfully dug a post hole under an existing deck. Always remember to prioritize safety when digging, and never hesitate to call a professional if you're unsure about any part of the process.