TxDOT Flex Base: Item 247 Specs Every Team Should Know

“TxDOT flex base” refers to the flexible base course governed by TxDOT Item 247. Grade selection comes down to pavement typical section and confinement, and every project needs to follow Item 247’s testing and placement rules to avoid rework. Get the grade wrong or skip a required test, and you’re looking at a corrective overlay or a rejected pay item down the line.

TL;DR:

• Correct Type and Grade selection depends on pavement thickness, confinement, traffic volume, and subgrade stability, with Grade 5 suitable for confined urban sections.
• Stabilization with cement, emulsion, foamed asphalt, or lime requires explicit plan authorization and affects testing and waiver conditions, especially for UCS and fines content.
• Delivery practices such as same-day placement, clean trucks, and documented stockpile sampling are essential to avoid contamination, delays, and rejection risk.
• Plans should explicitly specify the material Type, Grade, permitted recycled content, sampling procedures, measurement method, and any UCS or fines waivers to prevent disputes.
• Using the right material and following proper operational procedures ensure base performance and prevent early failure, rutting, or excessive roughness during ride quality testing.

Table of Contents

• What Is TxDOT Flex Base and Where Does Item 247 Apply?
• Material Types and Grades: What Each One Is For
• Key Test Requirements and Waiver Conditions in Item 247
• How to Pick the Right Grade and Type for Your Project
• Construction, Placement, and Payment Rules to Know
• Testing, Ride Quality, and What Causes Rejected Pay Items
• Coordinating Delivery and Stockpile Logistics on Site
• A Spec Writer’s Checklist Before You Bid
• Sourcing Compliant Flex Base for Your Next TxDOT Project
• Sources
• FAQ

What Is TxDOT Flex Base and Where Does Item 247 Apply?

Flexible base is the granular layer sitting between your subgrade and your surfacing course. It carries traffic loads, spreads stress downward so the subgrade doesn’t deform, and gives whatever asphalt or seal coat sits on top a stable platform to bond to. Without a properly specified base, even good surfacing fails early.

TxDOT Item 247 covers granular unbound base materials and defines the classification system engineers use to specify them: five Material Types (A through E) and four Grades (1-2, 3, 4, and 5). The item doesn’t work in isolation. It connects to proof-rolling requirements, compaction items, and the typical section shown on your plans.

A few things every spec writer should confirm before bidding:

• Which Type and Grade combination the typical section calls for
• Whether recycled or stabilized materials are permitted
• What lift thickness and compaction density the plans require
• Which test methods the district lab will run on delivered material

Material Types and Grades: What Each One Is For

Item 247’s five Types describe the source material, while the four Grades describe gradation, strength, and quality requirements. Type A is crushed stone, typically limestone, and is the workhorse for most highway and arterial projects. Type B covers crushed gravel. Type C is uncrushed gravel or caliche, generally reserved for lower-traffic rural work. Type D permits crushed concrete, either alone or blended, which matters if you’re pricing recycled content into a bid. Type E is a special material called out explicitly on the plans, often a local or regional source.

Grades work differently. TxDOT classifies flexible base into Grades 1-2, 3, 4, and 5, and the differences are about intended structural application, not a simple “better to worse” ranking:

• Grade 1-2 demands the tightest gradation and generally a minimum compressive strength, since it’s expected to be self-stable without much lateral support
• Grade 3 sits in the middle, used where moderate confinement exists
• Grade 4 allows a wider gradation band and is typically called out where plans specifically permit it
• Grade 5 can skip the unconfined compressive strength requirement, but only where the base has real lateral confinement from curbs, shoulders, or adjacent pavement

Pro Tip: Don’t assume Grade 5 is a downgrade from Grade 1-2. On a confined urban section with curb and gutter, Grade 5 material can perform just as well while giving you more sourcing flexibility.

Key Test Requirements and Waiver Conditions in Item 247

Four test methods drive nearly every flexible base compliance decision: Tex-104-E for liquid limit, Tex-106-E (Tex-10 series) for plasticity index, Tex-116-E (Tex-11 series) for wet ball mill degradation, and Tex-117-E for unconfined compressive strength. Add the #200 sieve wash for fines content, and you’ve got the core battery any testing lab runs on flex base samples.

Item 247 sets specific limits for each of these by Type and Grade, and gradation tables list percent passing at each sieve size. Here’s the part that trips up a lot of bid preparers:

• UCS and #200-sieve requirements are commonly waived when the base is treated with cement, emulsion, foamed asphalt, or lime, since stabilization changes how the material behaves structurally
• The waiver generally applies only when the plans call for stabilization or explicitly note the exception, not as a default assumption
• Additives and recycled content, including crushed concrete or reclaimed asphalt pavement, require plan authorization before you can substitute them into a mix

If your project anticipates stabilized base, get that waiver language written into the plans up front. Discovering it after material has already been tested and rejected is an expensive way to find out.

How to Pick the Right Grade and Type for Your Project

Grade selection isn’t a preference call. TTI’s flexible base selection guidance is blunt about this: choosing grade based on perceived material quality instead of the actual pavement typical section and confinement condition is a documented cause of premature failure, including rutting and early fatigue cracking under thin surfacing.

Work through these questions in order when specifying:

1. What’s the surfacing thickness? Thin asphalt or a seal coat over base puts more direct stress on the base layer, pushing you toward tighter-graded Grade 1-2 or Grade 3 material.
2. Is there lateral confinement? Curb, gutter, or adjacent shoulder pavement lets you consider Grade 5, which can skip the UCS test where confinement is documented.
3. What’s the traffic level? Higher-volume roadways generally warrant Grade 1-2 or Grade 3 regardless of confinement, since the margin for base movement shrinks.
4. What does subgrade stiffness look like? Soft or variable subgrade calls for a more self-stable base, again favoring Grade 1-2.
5. Does the project need Grade 4? Document this explicitly on plans; Grade 4’s wider gradation tolerance needs a clear typical section reference so bidders and inspectors aren’t guessing.

Construction, Placement, and Payment Rules to Know

Item 247’s construction clauses are specific about handling. Material has to arrive in clean trucks, get manipulated to stations no more than 100 feet apart or moved into designated stockpiles, and generally get spread the same day it’s delivered unless the Engineer approves otherwise. Skipping that same-day rule invites segregation and moisture inconsistency before compaction even starts.

Compaction targets run to 100% of maximum density unless plans state a different figure, with moisture held within a specified range through the lift. Watch these operational details:

• Stockpile height limits prevent segregation of coarse and fine particles
• Lift thickness has to match the plan-specified layer depth, not whatever a paver can handle in one pass
• Moisture control at compaction time is as critical as gradation control at the source

Payment follows one of three methods: cubic yard measurement in the original cross-section (CIP), roadway delivery by ton or cubic yard, or stockpile delivery measurement. The measurement method you bid under changes how you price haul distance and waste, so confirm it before you submit a number.

Testing, Ride Quality, and What Causes Rejected Pay Items

Ride quality is where a lot of otherwise-compliant base work runs into trouble. For final travel lanes receiving a one or two-course seal coat, TxDOT limits base surface roughness to no more than 100 inches per mile per 0.1-mile section, measured per wheel path. Any section exceeding that has to be corrected before the surface course goes down, which usually means blading, reworking, and recompacting a section you thought was finished.

Sampling and source verification follow a set frequency, and stockpile approval from the Engineer is required before delivery counts toward pay quantities on stockpile-measured items.

The three pitfalls that show up again and again on TxDOT jobs:

• Specifying Grade 5 on a section with inadequate confinement, then wondering why the base rutted
• Bringing in crushed concrete or RAP without plan authorization, which can trigger a rejected load
• Assuming a UCS waiver applies to unstabilized material when it doesn’t

Coordinating Delivery and Stockpile Logistics on Site

Meeting Item 247’s letter on paper means nothing if your material shows up contaminated or late. Plan deliveries around the 100-foot station requirement, and request source and test certificates before the first load rolls, not after a lab flags a gradation issue — as recommended in detail by why bridge construction needs on-site plants to improve material staging and handling.

A few habits keep projects clean:

• Insist on clean trucks between loads to avoid cross-contamination with other aggregate
• Push for same-day placement scheduling that matches your compaction crew’s availability
• Ask your supplier for stockpile sampling documentation alongside the delivery ticket
• Confirm scheduling commitments in writing when timing affects your compaction window

A road base delivery partner who can provide test certificates and consistent sourcing saves your QC team from chasing paperwork mid-project.

A Spec Writer’s Checklist Before You Bid

If you write specs for a living, add these callouts to every plan set involving flexible base: Type and Grade explicitly stated, permitted recycled content with limits noted, sampling and stockpile approval procedures referenced, the measurement method (CIP, roadway, or stockpile) named, and the IRI requirement flagged wherever a seal coat surface applies.

If you’re anticipating stabilized base, write the UCS/#200 waiver language directly into the plans rather than leaving it to interpretation during construction. Ambiguity here is where change orders come from. Bid documents that spell out these five items upfront cut down disputes over what “meets Item 247” actually means for that specific job, and they give the Engineer a much shorter list of questions to ask during submittal review.

— BRIAN

Sourcing Compliant Flex Base for Your Next TxDOT Project

Getting the spec right on paper is half the job. The other half is making sure what shows up on site actually matches it, load after load, without contamination or delay. Olearydevelopmentgroup handles that operational half for contractors and developers across the San Antonio area, running road base and stockpile delivery with clean trucks, GPS-tracked scheduling, and transparent per-load pricing that makes bid pricing easier to nail down upfront.

For crews specifying Grade 4 or Grade 5 material, Olearydevelopmentgroup carries both as ready stock, so you’re not waiting on a quarry allocation to hit your compaction window. Contractor accounts get net-30 invoicing and consistent source documentation to support your QC files. If you’re staging a job that needs flex base delivered on a schedule that matches your compaction crew, request a quote and get material moving before your window closes.

Sources

Plan-specified requirements always control over general guidance, so treat these as starting points, not substitutes for what’s on your project’s plan set: the Item 247 standard specification, the TxDOT Pavement Manual’s flexible base selection guidance, and the compiled 2024 Item 247 specification text from Texas A&M Transportation Institute.

• Section 3: Flexible Base Selection — TxDOT Pavement Manual
• s247.pdf — TxDOT standard spec for Item 247 (FTP)

FAQ

What Is Flex Base and What Is It Used For?

Flex base is the granular unbound layer specified under TxDOT Item 247 that sits between the subgrade and the surfacing course, distributing traffic loads and providing a stable platform for asphalt or seal coat.

Are Flex Base and Road Base the Same Thing?

Yes, in Texas highway construction, “flex base” and “road base” are used interchangeably to refer to material meeting Item 247’s classification and testing requirements.

What Is a Flexible Base Course?

A flexible base course is the structural layer of granular material, classified by Type (A through E) and Grade (1-2, 3, 4, 5) under Item 247, that supports the pavement surface and transfers load to the subgrade.

Is Flex Base Good for Driveways?

Flex base works well for driveways, especially projects that need a stable, well-draining subbase before an asphalt or gravel surface goes down. Olearydevelopmentgroup supplies road base sized for driveway applications across the San Antonio area.

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