The short answer: use SP-9.5 for thin surface lifts and repairs, SP-12.5 for surfaces or structural layers under moderate traffic, and SP-19 for structural and base layers that carry heavy loads. The right FDOT asphalt mix depends on the layer, the traffic and the lift thickness on your plans.
This post compares the three gradations we list at our Vero Beach plant and walks through how to choose between them.
What the numbers mean
All three are Superpave gradations. The number is the nominal maximum aggregate size in millimeters:
- SP-9.5: 9.5 mm stone, about three-eighths of an inch
- SP-12.5: 12.5 mm stone, about half an inch
- SP-19: 19 mm stone, about three-quarters of an inch
Stone size drives almost everything else: how thick each lift must be, how strong the layer is, and how smooth the finished surface looks. On FDOT plans these designations usually appear with a traffic level letter and a binder grade, and the full designation is what you order.
Side by side
SP-9.5: fine surface mix
- Best for: residential streets, surface courses, pothole and repair work, thin overlays
- Typical lift: about 1 to 1.5 inches compacted
- Strengths: smooth, tight finish; easy to hand-work; places thin
- Limits: less structural strength under heavy trucks
SP-12.5: surface or structural mix
- Best for: residential streets, commercial pads and parking, general surfacing
- Typical lift: about 1.5 to 2 inches compacted
- Strengths: versatile; stronger than SP-9.5 while still giving a good surface
- Limits: coarser texture than SP-9.5; needs a thicker lift
SP-19: structural or base mix
- Best for: structural and base layers, commercial pads, heavy-duty parking, the base of HOA and private roads
- Typical lift: about 2.5 to 3 inches compacted
- Strengths: strong stone skeleton spreads heavy loads
- Limits: open, coarse surface; usually covered by a finer surface course
The lift ranges come from a common rule of thumb: place a lift at least three to four times the nominal maximum aggregate size so the stone can compact. They are planning guides only. The thickness on your plans always controls.
Why lift thickness matters
Lift thickness is the most common reason a mix choice goes wrong. Try to place SP-19 at 1.5 inches and the large stones drag under the screed, tear the mat and leave it low on density. Place SP-9.5 too thick and it can be harder to compact evenly through the full depth. Choosing a gradation that fits the planned lift is the first check, before strength or appearance.
Matching mix to job
Our mix selection guide by application:
- Heavily traveled roads: Superpave, polymer-modified
- Residential streets: SP-9.5 or SP-12.5
- Commercial pads and parking: SP-12.5 or SP-19
- HOA and private roads: SP-19 base with SP-9.5 surface
- Pothole and repair work: SP-9.5 fine surface mix
Notice that many jobs use two mixes. A structural SP-19 layer carries the load, and an SP-9.5 or SP-12.5 surface gives a smooth, tight finish that sheds water. Building in layers like this is how most durable pavements are designed.
Don't forget the binder
A gradation is half the mix. Each is paired with a performance-graded binder, and we list PG 64-22 and PG 67-22 as standard grades and PG 76-22 as polymer-modified. Two jobs can use the same SP-12.5 gradation with different binders: a quiet residential street on a standard grade, and a busy commercial entrance on a polymer-modified grade to resist rutting where trucks turn and stop. Our specifications page lists the full set, with availability confirmed per project.
Florida factors
- Heat: slow, heavy traffic in summer is what causes rutting. Coarser structural mixes and stiffer binders help where loads concentrate.
- Rain: density keeps water out. Pick a gradation that suits the lift so the crew can reach target compaction.
- Seasonal traffic: many Treasure Coast roads and lots carry much heavier traffic in winter. Design for the busy season, not the quiet one.
Common mix selection mistakes
- Substituting a mix without approval: on agency or engineered work, swapping SP-12.5 for SP-9.5 because it is easier to place can get the work rejected. Get any change approved first.
- Using a fine mix as the only layer under trucks: a thin SP-9.5 mat over a weak base will not carry heavy loads for long.
- Ordering the gradation but not the binder: the plant needs both to produce the right mix.
- Estimating every layer as one number: each mix is a separate order line, so calculate tons per layer.
A quick way to decide
- If the plans specify a mix, order exactly that.
- Identify the layer: base, structural or surface.
- Check the planned lift thickness against the stone size.
- Consider the traffic, especially trucks and stopping vehicles.
- Pick the binder to match.
- Estimate tonnage with our asphalt tonnage calculator.
Still unsure? Describe the application and our team will recommend the mix type, grade, tonnage and scheduling.
Order from our Vero Beach plant
Call or text (772) 494-6077 to confirm availability and book a pickup window, or send details through our contact page. Pickup runs Monday through Friday, 8am to 5pm, first come, first served, at 500 2nd St SW, Vero Beach, FL 32962.