By The Roofing Brief Team. Last reviewed: October 2026.
The best cap stapler for roofing underlayment in 2026, for most crews, is the Stinger CH38-2 Cap Hammer: a 2.6 lb airless hammer tacker that drives a 3/8 in staple through a 1 in plastic cap, holds 168 staples and caps, and lists at $59.99 at Nail Gun Depot (October 2026). It needs no compressor or hose. For large decks, the pneumatic Stinger CS150B ($270.42) adds 5/8 to 1-1/2 in staple legs. Where the 2021 IRC requires wind design, the underlayment table names ring or deformed shank cap nails, so a cap nailer such as the Stinger CN100B replaces any cap stapler.
This roundup is compiled from manufacturer product pages and owner’s manuals, retailer listings checked in October 2026, and the 2021 International Residential Code. We did not run hands-on tests. Prices are single-retailer list prices on the date checked and change often.
Best cap staplers for roofing underlayment at a glance
The table compares five tools on drive type, weight, fastener, capacity and October 2026 list price, with the source for each row. A manual hammer tacker such as the Stinger CH38-2 costs about one fifth of a pneumatic stapler. A pneumatic stapler such as the Stinger CS150B fires up to 5 cap staples per second. A cap nailer is the tool the IRC wind-design table points to.
| Tool | Type | Weight | Fastener | Capacity | List price (Oct 2026) | Best for | Source |
|---|---|---|---|---|---|---|---|
| Stinger CH38-2 Cap Hammer | Manual hammer tacker (airless) | 2.6 lb | 3/8 in staple + 1 in plastic cap | 168 staples and caps | $59.99 | Top pick: most crews, mobility, value | Stinger; Nail Gun Depot listing |
| Stinger CS150B | Pneumatic cap stapler | 4.2 lb | 18 ga staples, 5/8, 7/8, 1-1/4 and 1-1/2 in legs + 1 in cap | 200 staples and 200 caps | $270.42 | High-volume crews, large decks, variable leg length | CS150B owner’s manual; Nail Gun Depot |
| Bostitch SL1838BC | Pneumatic cap stapler kit | 3.9 lb (Bostitch spec as listed by dealers) | 18 ga, 3/4 to 1-1/2 in legs + 1 in cap | 160 staple magazine | $235.00 | Crews standardized on Bostitch and Stanley air tools | Nail Gun Depot listing |
| Stinger CH38A | Auto-feed manual hammer tacker | 3 lb (retailer listing) | 3/8 in staple + 1 in plastic cap | 168 staples and 168 caps | $82.26 | Airless crews who want an auto-feed cap | Stinger; Nail Gun Depot |
| Stinger CN100B | Pneumatic cap nailer | 4.9 lb (retailer listing) | 1 in x 0.083 in nail + 1 in plastic cap | 200 nails and caps | $346.86 | Wind-design areas and exposed underlayment | Stinger; Nail Gun Depot |
Which fastener the job needs: decision table
| If your job is | Use | Rule behind it |
|---|---|---|
| Asphalt shingles, outside an IRC wind-design region, shingles on the same day | Cap stapler with 1 in caps (CH38-2, CH38A or CS150B) | 2021 IRC Table R905.1.1(3): underlayment “fastened sufficiently to hold in place”, unless the underlayment instructions say otherwise |
| Any roof covering inside a wind-design region (IRC Figure R301.2.1.1) | Cap nailer: ring or deformed shank nails with 1 in caps | 2021 IRC Table R905.1.1(3): 12 in grid between side laps, 6 in at side and end laps, shank at least 0.083 in |
| Sheathing thicker than the 3/8 in staple leg reaches into, in a wind-design region | Cap nail long enough to pass through the deck or reach at least 3/4 in into it | 2021 IRC Table R905.1.1(3) shank length rule |
| Underlayment left exposed longer than the maker’s stated exposure window | Cap nails, per the product instructions | Underlayment data sheet; the code defers to it in non-wind-design areas |
| Repair and small-deck work with no compressor on site | Manual cap hammer (CH38-2 at $59.99) | Price gap: $270.42 for the CS150B vs $59.99, Nail Gun Depot, Oct 2026 |
| Full-deck production work with an existing 80 to 110 psi air setup | Pneumatic cap stapler (CS150B or SL1838BC) | CS150B manual: 80 to 110 psi, 200-cap reel |
How we picked
We ranked tools editorially on five published criteria: whether the tool drives the 1 in cap named in 2021 IRC Table R905.1.1(3), drive type and whether it needs a compressor, listed weight and magazine size, staple or nail length range, and October 2026 list price. Sources were Stinger product pages and the CS150B owner’s manual, Nail Gun Depot listings, and the ICC code text. We did not disassemble or bench-test any tool.
Top pick: Stinger CH38-2 Cap Hammer 2.0
The Stinger CH38-2 Cap Hammer is the best cap stapler for most roofing crews because it delivers a 1 in plastic cap with no air setup. At 2.6 lb it holds 168 staples and 168 caps, drives a 3/8 in staple from Stinger StaplePac strips only, and lists at $59.99 at Nail Gun Depot (October 2026). The trade-off is a swing tool with one fixed 3/8 in leg length, which also means it cannot meet the IRC wind-design table, since that table calls for nails.
- Pros: Lowest cost of entry at $59.99, no air setup, 2.6 lb, 1 in cap.
- Cons: Manual swinging on big roofs, single 3/8 in staple length, not a nail tool for wind-design regions.
- Best for: Repair crews, small to mid-size decks, and any contractor who wants one airless tool under $60.
Best pneumatic for high-volume crews: Stinger CS150B
The Stinger CS150B is the pick when a crew covers large decks all day and wants to vary staple length. Its owner’s manual lists 4.2 lb, an 80 to 110 psi operating range, a 1/4 in air inlet, 200 staples in two 100-count strips and a 200-cap reel, with 18 gauge StaplePac staples in 5/8, 7/8, 1-1/4 and 1-1/2 in legs. Stinger lists bump-fire or sequential firing and up to 5 cap staples per second. It lists at $270.42 at Nail Gun Depot (October 2026), and the manual gives a one-year warranty on cap assemblies and housing castings and 90 days on most other parts.
- Pros: 5 cap staples per second, four leg lengths from 5/8 to 1-1/2 in, 200-cap reel, two firing modes.
- Cons: Needs a compressor and hose at 80 to 110 psi, 4.2 lb, about 4.5 times the CH38-2 price.
- Best for: Production crews on large residential or light commercial decks.
Best for Bostitch and Stanley crews: Bostitch SL1838BC
The Bostitch SL1838BC suits crews already running Bostitch and Stanley pneumatics who want shared fittings, parts and dealer support. Dealers list it at 3.9 lb with a 160-staple magazine, 18 gauge staples from 3/4 to 1-1/2 in with a 1 in cap, tool-free depth of drive, and sequential or contact firing. It ships as a kit with a carrying case and starter caps and staples, and lists at $235.00 at Nail Gun Depot (October 2026).
- Pros: Adjustable depth of drive, kit packaging, Bostitch dealer and parts network, dual trigger modes.
- Cons: Needs air, shortest leg is 3/4 in vs 5/8 in on the CS150B.
- Best for: Shops standardized on the Bostitch and Stanley air platform.
Best auto-feed manual: Stinger CH38A
The Stinger CH38A is the airless pick for crews who like the hammer tacker format but want the cap advanced automatically. Stinger describes a gravity feed with an auto-feed feature that positions the 1 in plastic cap for the 3/8 in staple, and the tool holds 168 caps and 168 staples. It lists at $82.26 at Nail Gun Depot (October 2026), $22.27 more than the CH38-2, and the retailer lists it at 3 lb.
- Pros: Airless, auto-feeds the cap, 168-count load.
- Cons: Still a swing tool, $22.27 more than the CH38-2, fixed 3/8 in staple length.
- Best for: Airless crews who want fewer misfed caps.
Best when underlayment stays exposed: Stinger CN100B cap nailer
When underlayment will sit exposed past the maker’s window, or the roof is in an IRC wind-design region, a cap stapler is the wrong tool and a cap nailer like the Stinger CN100B is the right one. Stinger lists it as firing 1 in x 0.083 in nails with full 1 in plastic caps at up to 5 per second, delivering cap nails that “pass 2012 ICC building codes”, and approved for the IBHS FORTIFIED Roof program. Nail Gun Depot lists it at 4.9 lb, 200 capacity, 80 to 110 psi and $346.86 (October 2026). The 0.083 in shank matches the minimum in 2021 IRC Table R905.1.1(3).
- Pros: Nails meet the IRC wind-design fastener rule, 5 per second, FORTIFIED Roof approval per Stinger.
- Cons: Highest price here at $346.86, needs a compressor, 4.9 lb.
- Best for: Underlayment left exposed past a manufacturer window, and wind-design regions.
Cap stapler vs cap nailer: which does your job need?
Choose a cap stapler when the roof is outside an IRC wind-design region and shingles go down promptly, and choose a cap nailer when the roof is inside one or the underlayment stays exposed. The 2021 IRC lets asphalt-shingle underlayment be “fastened sufficiently to hold in place” outside wind-design regions, and some synthetic underlayment instructions allow staples there. Inside wind-design regions the same table names annular ring or deformed shank nails, so staples are out.
- Same-day shingles, outside a wind-design region: A cap stapler with a 1 in cap meets 2021 IRC Table R905.1.1(3) unless the underlayment instructions ask for more.
- Underlayment exposed past the maker’s stated window: Move to cap nails if the product instructions require them for extended exposure.
- Inside a wind-design region (IRC Figure R301.2.1.1): Cap nails with a shank of at least 0.083 in, on a 12 in grid between side laps and 6 in at side and end laps.
- Warranty-sensitive system: Read the shingle and underlayment instructions first, because a fastener the maker does not list can affect coverage.
What building code and warranties require for cap fasteners
Building code sets the cap and shank rules that most buying guides skip. In the 2021 IRC, Table R905.1.1(3) covers underlayment application. Where wind design is not required, asphalt-shingle and tile underlayment is “fastened sufficiently to hold in place”, and metal, slate and wood roofs follow the manufacturer’s instructions. Where wind design is required, the table requires 1 in diameter metal or plastic caps on annular ring or deformed shank nails.
| 2021 IRC Table R905.1.1(3) rule (wind-design areas) | Minimum | What it means on the roof |
|---|---|---|
| Cap diameter | 1 in, metal or plastic | All five tools above drive a 1 in cap |
| Metal cap thickness | 32 gage sheet metal; power-driven metal caps 0.010 in | Applies to tin-cap nails, not the plastic caps above |
| Plastic cap edge thickness | 0.035 in | Check the cap spec on the fastener box |
| Nail shank | 0.083 in; annular ring or deformed shank | The Stinger CN100B nail is listed at 0.083 in; a staple does not qualify |
| Shank length | Through the sheathing, or at least 3/4 in into it | A 1 in cap nail passes through 1/2 in or 5/8 in sheathing; a 3/8 in staple leg does not |
| Fastener pattern | 12 in grid between side laps; 6 in at side and end laps | Plan on far more fasteners per square than a field-only pattern |
The same 2021 IRC wording appears in adopted local versions such as the 2021 Seattle Residential Code, Chapter 9. Older editions differ: the 2012 IRC section R905.2.7.2 triggered the grid pattern at a 120 mph basic wind speed and named ASTM D226 Type II, ASTM D4869 Type IV or ASTM D6757 underlayment. Confirm which edition your jurisdiction enforces before you choose the tool.
Warranty terms can be stricter than code. Shingle makers tie coverage to installing their listed underlayment by their printed instructions, so if the instructions name cap nails for an exposed install, a cap stapler on that job can affect the warranty. For the layer beneath these fasteners in leak-prone areas, see our guide to the best ice and water shield.
For the shingle nailing that follows underlayment, compare options in our guide to choosing a coil roofing nailer. For the blade work around valleys and laps, see the best roofing knife. Underlayment work puts crews on bare, slick decks, and our DIY roofing injury report covers the fall data behind putting fall protection on the same order as any fastening tool.
Frequently asked questions
Can you staple synthetic underlayment?
Often yes, outside an IRC wind-design region and when the underlayment instructions allow staples. The 2021 IRC lets asphalt-shingle underlayment be fastened sufficiently to hold in place there, and a 1 in plastic cap spreads the load. Inside a wind-design region, Table R905.1.1(3) requires ring or deformed shank cap nails, so staples do not qualify.
What size cap staple do I need for roofing underlayment?
Use a 1 in diameter cap, the size the 2021 IRC names for cap fasteners. Leg length depends on the tool: the Stinger CH38-2 and CH38A use a 3/8 in staple, the CS150B takes 5/8, 7/8, 1-1/4 and 1-1/2 in legs, and the Bostitch SL1838BC takes 3/4 to 1-1/2 in. Match the leg to your sheathing and the underlayment data sheet.
Is a cap stapler or cap nailer better for underlayment?
A cap stapler is faster and cheaper, from $59.99 for the Stinger CH38-2, and works outside IRC wind-design regions when shingles follow promptly. A cap nailer such as the Stinger CN100B is required inside wind-design regions, where the IRC names nails with a shank of at least 0.083 in on a 12 in grid.
Do you need a compressor for a cap stapler?
Not always. The Stinger CH38-2 and the auto-feed CH38A are airless hammer tackers. Pneumatic staplers such as the Stinger CS150B and Bostitch SL1838BC need a compressor and hose; the CS150B manual lists 80 to 110 psi.
Why does underlayment need a plastic cap and not just a staple?
The 1 in cap spreads the fastener load over a wider area so the membrane resists tearing at the fastener. The 2021 IRC sets a 1 in minimum cap diameter and a 0.035 in plastic cap edge thickness for wind-design regions, and a bare staple or nail without a cap does not meet that rule.