Portable Buildings in Texas - Sizes, Tips & Buying Guide

Pressure-Treated Portable Building Skids: Should You Use Ground, Gravel, or Concrete Blocks?

When purchasing a portable building, one of the most important decisions is preparing the ground underneath it. Should you set the building’s pressure-treated skids directly on the ground, place them on a gravel pad, or support them with concrete blocks? Each option has advantages, and the right choice depends on your property’s soil conditions, drainage, slope, and the size and design of your building. For Texas property owners, where heavy rain, hot summers, and changing soil conditions can affect the ground beneath a portable building, understanding your foundation options can help you make a better decision.

At JM Portable Buildings, we want our customers to understand how proper site preparation can help protect their investment and provide a stable foundation for years to come. Let’s look at how pressure-treated skids work and compare the three most common installation options.

What Are Pressure-Treated Skids on a Portable Building?

Skids are the long support runners located underneath a portable building. They help distribute the building’s weight across the supporting surface and allow the building to be moved when its design permits. Pressure-treated skids are lumber that has been treated with preservatives to help protect against wood decay, fungi, and wood-destroying insects. Because skids are located underneath a building, they may be exposed to ground moisture, humidity, rainwater, and damp conditions. Pressure treatment helps the wood resist deterioration, making it a practical choice for many portable building applications. However, pressure-treated wood is not waterproof, and pressure treatment does not eliminate the need for proper drainage and support. Keeping the area underneath your building as dry as reasonably possible remains important, even when the skids are pressure-treated.

1. Setting Pressure-Treated Skids Directly on the Ground

One option is to place your portable building directly on firm, reasonably level ground, with the pressure-treated skids resting on the prepared soil.This can be a practical approach when the site has suitable soil conditions and drains properly.

Advantages of Setting Skids on the Ground

Less site preparation

If your property already has a firm, level area with good drainage, you may not need to construct a separate gravel pad.

Potentially lower initial cost

Using an existing suitable area can reduce the amount of material and labor required before delivery.

Pressure-treated wood offers added protection

Pressure-treated skids are designed to resist certain forms of wood deterioration. This provides an advantage over untreated lumber when the skids encounter damp conditions.

What Are the Disadvantages?

Even pressure-treated skids can experience problems when they remain in persistently wet conditions. Soil can hold moisture against the bottom of the skids, particularly in areas with poor drainage. Soft ground can also compress beneath the building’s weight, potentially causing uneven settling. In Texas, some soils expand when wet and shrink during dry weather. These changes can affect the stability of a building over time.

Other concerns include:

Standing water beneath the building.
Uneven settling on soft soil.
Mud and vegetation collecting around the skids.
Reduced airflow underneath the building.
Greater difficulty inspecting the underside when the building sits very close to the ground.

When Does This Option Make Sense?

Setting pressure-treated skids directly on the ground may be appropriate when the soil is firm, the area is properly graded, and the building manufacturer’s installation requirements permit it. Avoid placing a building on loose topsoil, soft ground, or an area where rainwater regularly collects.

Our tip: Pressure-treated skids provide added resistance to decay, but they are not a substitute for a stable, well-drained site.

2. Setting Pressure-Treated Skids on Gravel or Crushed Rock

For many portable building installations, a properly prepared gravel pad is an excellent option. A gravel pad can provide a more consistent supporting surface while helping rainwater drain away from the area beneath the building. When pressure-treated skids rest on a properly prepared gravel surface, the combination can help reduce some of the moisture and stability concerns associated with poorly drained soil.

Advantages of a Gravel Pad

Better drainage

Properly selected and installed gravel can allow water to drain through the aggregate rather than collect around the skids. The finished pad should also be graded so surface water flows away from the building.

A more consistent supporting surface

When the underlying soil is prepared correctly and the gravel is properly compacted, the pad can provide a more uniform surface for the building’s skids.

Reduced mud and standing water

A properly designed gravel pad can help reduce muddy conditions and improve the area surrounding the building.

Works well with pressure-treated skids

Pressure-treated skids offer resistance to decay, while a well-prepared gravel pad can help manage moisture and provide suitable support. These features complement each other, although neither guarantees that moisture or settling problems will never occur.

A cleaner appearance

Gravel can provide a finished look around a portable building and make the surrounding area easier to maintain.

How Should You Prepare a Gravel Pad?

The correct pad dimensions and depth depend on the building, soil conditions, and site requirements. For many standard portable buildings, a compacted gravel layer approximately 4 to 6 inches deep may be a reasonable starting point. Some sites require more extensive preparation.

Here are the basic steps to consider:

Choose a suitable location. Avoid low areas where water collects after heavy rain.
Remove vegetation. Clear grass, roots, and unsuitable topsoil from the pad area.
Evaluate the soil. Soft or unstable soil may require additional preparation before placing gravel.
Prepare the base. Establish a stable, appropriately graded surface.
Add suitable gravel. Use an aggregate appropriate for the soil and intended application.
Compact and level the pad. A properly compacted surface is more stable than loose rock.
Check the finished elevation. Ensure the pad supports the skids as required and allows water to drain away from the building.

Extending the pad beyond the building’s footprint may help reduce erosion and muddy conditions around the perimeter. The gravel should provide proper support rather than creating an uneven surface with isolated high or low spots.

Is Gravel Better Than Setting Skids on Bare Ground?

In many situations, a properly prepared gravel pad offers advantages over bare soil. It can improve drainage, provide a more consistent base, and help keep the area around the building cleaner. However, gravel alone will not solve every foundation problem. If the underlying soil is unstable or water continually flows beneath the building, additional site work may be necessary.

Our tip: If you are investing in a portable building that you plan to keep for many years, consider the long-term benefits of preparing the site properly before delivery.

3. Setting Pressure-Treated Skids on Concrete Blocks - Highly recommended by JM

Another common option is to support a portable buildings' skids on concrete blocks. Rather than resting continuously on the ground or a gravel pad, the skids are supported at designated points beneath the structure. Concrete supports can be useful when a building needs to be raised slightly above the surrounding ground or when the site has modest variations in elevation. However, the blocks must be positioned correctly and supported by a stable base.

Advantages of Concrete Blocks

Can help level the building

Properly positioned supports can help accommodate minor differences in ground elevation, provided the installation follows the manufacturer’s requirements.

Elevates the skids

Raising the skids above the surrounding soil can help reduce direct contact with wet ground.

Provides access underneath the building

Depending on the building’s height and support arrangement, elevation may make it easier to inspect the skids and underside.

Can work with pressure-treated skids

Pressure-treated skids can be supported by appropriate concrete supports when the support locations, spacing, and loads meet the building’s requirements.

What Should You Watch Out For?

Concrete blocks must rest on a firm, stable surface capable of supporting the loads transferred through them. Placing blocks directly on soft soil can allow them to sink or shift. Stacking blocks improperly or using unsuitable masonry units can also create an unstable support system.

Additional concerns include:

Uneven settling beneath individual blocks.
Improper spacing between support points.
Inadequate support beneath the building’s skids if not correctly blocked.
Shifting on sloped or unstable ground.

Concrete blocks are not automatically a better foundation simply because they raise the building above the ground. The number of supports, their placement, their load capacity, and the preparation beneath them all matter.

Should You Put Gravel Under Concrete Blocks?

Depending on the site and installation design, a properly prepared base beneath concrete supports may help provide stable bearing. However, simply placing loose gravel beneath a block does not guarantee stability. The supporting surface must be prepared appropriately for the soil conditions and the building’s weight. Follow the manufacturer’s instructions regarding suitable support materials and installation methods.

Our tip: Never guess at the spacing or height of concrete supports. A building must be supported according to its design and installation requirements.

4. Ground vs. Gravel vs. Concrete Blocks:

Which Is Best for Pressure-Treated Skids?

All three methods may be suitable in the right circumstances. The best choice depends on the building and the property where it will be installed.

Installation Method 1. Main Advantage 2. Main Concern 3. Important Consideration

A. Directly on suitable ground

1. Less site preparation 2. Moisture & uneven settling 3. Soil must be firm & well-drained

B. Gravel or crushed rock

1. Drainage & a consistent supporting surface 2. Requires proper preparation & compaction 3. The underlying soil must also be stable

C. Concrete blocks

1. Can elevate & support designated points beneath the skids 2. Supports can shift or settle 3. Correct block placement and stable bearing are essential

Which Option Would We Consider First?

For many Texas properties, a properly prepared gravel pad is an excellent option to consider. It can provide a consistent supporting surface and help manage drainage around pressure-treated skids. However, it is not the only acceptable solution. Suitable ground may work for certain buildings, and appropriately installed concrete supports may be useful for other installations. The important thing is to match the foundation to the building and the site rather than assuming one method works for every situation.

5. Why Pressure-Treated Skids Still Need Proper Drainage

One of the biggest misconceptions about pressure-treated wood is that it can be exposed to moisture indefinitely without consequences. Pressure treatment helps protect wood against certain types of deterioration, but it does not make the lumber waterproof or immune to every form of damage. Repeated or prolonged wetting can still create unfavorable conditions around the skids and other building components. Proper drainage helps limit the time water remains beneath the building.

Here are a few ways to help manage moisture:

Avoid placing the building in a low spot.
Direct surface water away from the structure.
Keep gutters and roof runoff from creating persistent wet areas beneath the building.
Avoid allowing soil, leaves, and vegetation to accumulate around the skids.
Inspect the area beneath the building periodically for standing water or signs of movement.
Address drainage problems promptly rather than assuming pressure-treated wood will solve them.

A well-drained site benefits the entire building, not just the skids.

6. Why Proper Leveling and Support Matter

Regardless of whether you choose ground, gravel, or concrete blocks, the building needs adequate support and must be installed according to the manufacturer’s specifications.

Uneven support or settlement can contribute to problems such as:

Doors that become difficult to open or close.
Floors that feel uneven.
Stress on structural components.
Changes in the building’s level.
Water collecting around the foundation area.

Pressure-treated skids help support the building, but they cannot prevent the ground beneath them from shifting or compressing. Likewise, a gravel pad or concrete blocks cannot guarantee that settlement will never occur. Proper site preparation, support placement, and drainage work together to help reduce these risks.

7. Preparing Your Property for a Portable Building in Texas

Before your JM Portable Building arrives, spend some time evaluating the installation area.

Choose a Well-Drained Location

Look at the property after a heavy rain if possible. Areas that retain water may require additional preparation.

Consider Your Soil

Some Texas soils change volume as moisture levels rise and fall. If the soil is soft, expansive, or unstable, additional preparation may be necessary.

Plan for Water Runoff

Water from the roof and surrounding property should drain away from the building rather than collect underneath it.

Allow for Proper Support

The building’s skids need appropriate bearing along the support arrangement specified by the manufacturer.

Confirm Site Requirements Before Delivery

Make sure the ground, gravel pad, or concrete supports meet the requirements for your particular building. Depending on your location, local building codes, permits, setbacks, or other requirements may also apply. Preparing ahead of time can make delivery smoother and help reduce the chance of avoidable problems after installation.

Frequently Asked Questions About Pressure-Treated Portable Building Skids

Can pressure-treated skids sit directly on dirt?

They may be able to rest on suitable, well-drained ground if the building’s installation requirements permit it. However, pressure-treated wood is not waterproof, and prolonged contact with wet soil can still contribute to deterioration.

Is gravel better than dirt under pressure-treated skids?

A properly prepared gravel pad often provides better drainage and a more consistent supporting surface than bare soil. The result depends on the underlying soil, the gravel used, and how the pad is constructed.

Can I set pressure-treated skids on concrete blocks?

Yes, when the building is designed for that support arrangement and the blocks are appropriate for the loads. Their placement, spacing, stability, and the surface beneath them must meet the manufacturer’s requirements.

Do pressure-treated skids rot?

Pressure treatment helps resist wood decay, but it does not make lumber completely immune to deterioration. The level of protection depends on the treatment, its intended use, and the conditions to which the wood is exposed.

Does pressure-treated wood need to stay dry?

Pressure-treated wood is designed to tolerate certain exposure conditions, but keeping it from remaining continuously wet is still beneficial. Good drainage and airflow can help reduce prolonged moisture exposure.

How deep should a gravel pad be for a portable building?

There is no single depth that works for every property. A compacted layer approximately 4 to 6 inches deep may be suitable for some standard installations, while soft soil, heavier buildings, or difficult drainage conditions may require a different design.

Do pressure-treated skids eliminate the need for a foundation?

No. The skids are part of the building’s support system, but the ground beneath them still needs to provide suitable support. The required foundation or site preparation depends on the building design and the manufacturer’s instructions.

Final Thoughts: Protect Your Portable Building from the Ground Up

Pressure-treated skids are an important feature of many portable buildings because they help support the structure while offering added resistance to wood decay. But the way those skids are supported matters, too. Setting them directly on suitable ground may work for some properties. A properly prepared gravel pad can provide excellent drainage and a consistent surface. Concrete blocks may be appropriate when installed correctly and when the building is designed for that type of support. For many Texas property owners, the best starting point is a stable, level, well-drained installation area that meets the manufacturer’s requirements. Taking the time to prepare your site before delivery can help protect your investment and make ownership easier over the long term.

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