Slate and concrete tile occupy a similar position in the Florida market — both are heavy, durable, premium-tier roofing materials. The Florida Building Code, however, treats them differently in several specific ways. Understanding these distinctions matters for specification, attachment, and insurance.
Distinction 1: Attachment standards
Concrete tile is governed by the RAS series (118, 119, 120, 127) for attachment. The methods are well-documented and applied to many concrete tile products with broadly similar attachment requirements.
Slate has its own attachment requirements, derived from the slate industry's traditional installation methods adapted to current code. Slate is typically attached with two slate nails per tile, through pre-drilled holes (for thicker stock) or pre-formed nail slots. The attachment is per-tile and specified by the slate's product approval.
The two methods are not interchangeable. A roof attached "per RAS 120" is concrete tile. A slate roof has a slate-specific attachment that does not have a RAS number.
Distinction 2: Wind-uplift testing
Concrete tile is tested under TAS 110 and TAS 114 with attachment patterns specified by the manufacturer.
Slate is tested under different protocols that account for its weight, the way it lies flat against the deck, and its lower wind profile. The wind-uplift performance is generally higher than concrete tile at equivalent attachment, because the slate's lower profile generates less uplift per square foot.
Distinction 3: Product approval
Concrete tile is typically approved as a complete system — the tile, the underlayment, and the attachment method together as an FPA or NOA.
Slate is typically approved by component — the slate itself has a Florida Product Approval, but the assembly is specified by the engineer or by reference to the slate industry's installation standards. There is no single "slate roof NOA" the way there is a concrete tile NOA.
This affects what your closeout package looks like. A slate roof's closeout will reference the slate's product approval plus the underlayment's approval plus the engineer's attachment specification — three documents, not one.
What this means for an owner
Three practical implications:
1. Specification clarity
When ordering a slate roof, the specification needs to be more detailed than for a concrete tile equivalent. The contractor cannot simply reference an NOA; the specification must enumerate the slate type, the attachment pattern, the underlayment, and the flashing materials. We write substantially longer specifications for slate than for concrete tile.
2. Inspection process
The inspection process is similar but the inspector's reference documents differ. A slate roof inspection looks at attachment per the engineering specification rather than per a standardized NOA pattern.
3. Insurance documentation
The wind-mitigation report's documentation needs to capture the slate-specific assembly. Inspectors familiar primarily with concrete tile installations sometimes use shorthand that does not properly document slate. We recommend slate-experienced inspectors for these reports.
A note on weight
Slate weight runs 800-1,200 lbs per square depending on thickness. Concrete tile weight runs 850-1,100 lbs per square. The two are similar in dead load; the structural framing required is comparable.
Where they differ in load is wind uplift. Slate's flat profile produces less uplift per square foot than concrete tile's deeper profiles, which can simplify attachment calculations.
What we typically install
Both. The choice between slate and concrete tile is rarely about the code differences — it is about architecture, budget, and longevity expectations.
Slate is the longer-lifespan, higher-cost, more architecturally serious choice. Concrete tile is the more affordable, broadly-applicable choice that performs well within its expected service life.
The code accommodates both; the distinctions above are technical, not preferential.
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