Screws vs Nails, and How Many You Need

Almost every page on this question answers it as a contest, as though one fastener were better than the other everywhere. The code does not work that way and neither does a joist hanger. Each connection names its own fastener, sometimes by type and diameter, and where it does, the other one is not an equivalent you may choose. This is what is actually specified, and the counts for the one connection where you genuinely do choose.

By Lucas Pradella, builder and editor. Checked 2026-09-16.

There is no code contest between screws and nails

The question people search is which is stronger. The sources this site works from do not answer it, and it is worth saying so plainly: no document cited on this page publishes a shear strength comparison between a deck screw and a nail. Manufacturers publish rated values for their own listed fasteners in their own listed connections, and that is a different kind of statement from a general ranking.

What the code does instead is name the fastener for the connection. Sometimes it names a type and a diameter, sometimes it names only the metal, and sometimes it says nothing at all and leaves the question to the manufacturer. Where a connection names a fastener, the other kind is not a substitute unless it is listed for that connection. That single sentence settles more real arguments on site than any strength table would.

So the useful version of the question is not which is stronger. It is: which of these three situations am I in.

• The code names the fastener. Use it. The deck ledger is the clearest example.
• A manufacturer names the fastener. Use it, and fill every hole. Joist hangers and hidden decking clips are here.
• Nothing names it. Then you choose, and the code still constrains the metal. Face-fastened decking is here.

Where the code names the fastener: the ledger

Deck collapses are ledger failures, and the prescriptive answer is IRC Table R507.9.1.3(1). Read the column headings before the numbers, because the headings are the finding: the table has three fastener columns and all three are a 1/2 in diameter lag screw or a 1/2 in diameter bolt, differing only in whether there is up to 1/2 in or up to 1 in of sheathing in the stack.

There is no nail column. There is no structural wood screw column either. A proprietary structural screw may well be tested and approved for a ledger, but it is approved under its own evaluation report and its own spacing, not under this table. Substituting it and keeping the table's spacing is using a number that was never about your fastener.

The table's footnote d is the other trap, and it costs nothing to get right: the tip of the lag screw must fully extend beyond the inside face of the band joist. A lag that stops inside the band joist is not the fastener that was tested, no matter how correct the spacing above it looks.

Two more limits from the same section matter more than fastener choice ever will. A ledger may not support concentrated loads from beams or girders, and it may not be supported on stone or masonry veneer. Veneer is hung on the building rather than holding it up. And the vertical fasteners in that table do not provide the lateral load connection, which is a separate device under R507.9.2: either two hold-downs of not less than 1,500 lb capacity within 24 in of each end of the deck, or four of not less than 750 lb.

Where the manufacturer names it: joist hangers

A joist hanger is rated as an assembly, and the rating is tied to a particular fastener at a particular diameter filling a particular set of holes. That is why a deck screw is not a hanger nail. It is not that the screw is weak, it is that the screw was not what the published capacity was established with, so the capacity no longer describes what you built.

The same logic makes partial nailing a defect rather than a shortcut. A hanger with half its holes filled is not at half capacity in any published sense, because no published capacity describes it.

Hidden decking clips work the same way. They are proprietary, they are not interchangeable between brands even where they look identical, and their fastener count and screw come from the manufacturer's instructions. The same is true of composite decking generally. IRC R507.7 sends plastic composite decking to Section R507.2, which routes to ASTM D7032 and the manufacturer's published instructions, so the code sets no joist spacing for it at all.

For structural panels, IRC R602.10 braced wall panels carry their own fastening schedules, tighter than general practice. This site does not reproduce the IRC fastening schedule table, so no nail size for it is printed here. Take that one from the code edition your jurisdiction enforces.

How many deck screws you need

Face-fastened decking is the connection where nobody names the fastener for you, and it is the one people are actually counting. The convention is two fasteners per board at every joist crossing, which is a trade practice rather than a code table, and it exists because one fastener lets a board cup and rotate around it.

Multiply two counts: the rows of board that fit across the deck, and the joists each row crosses. Rows come from the actual board width plus the gap, not the nominal width, and the joist count carries a plus one for the closing joist at the far end, which is the term people drop.

Now the finding, and it is the one worth keeping: across every deck in that table the answer lands between 3.36 and 3.61 screws per square foot. That is our arithmetic on the same convention applied at 16 in centers with 5 1/2 in boards, and the narrowness is not an accident. Both grids scale with the deck, so the ratio is almost fixed and only the rounding on the last board row moves it.

Which gives you a check anyone can run in their head. Multiply the deck area by 3.5. A 192 sq ft deck comes out at 672 against the exact 676, and a 400 sq ft deck at 1,400 against 1,376. If a supplier or an estimate hands you a figure that is not near your area times three and a half, one of you has the joist spacing or the board width wrong.

Joist spacing moves the count more than the deck size does

The input that surprises people is not the deck dimension, it is the joist spacing, because it multiplies every board row at once.

A third more screws, a third more hangers and a third more hanger nails, from a decision made for a completely different reason. Twelve inch centers turn up for diagonal decking layouts and for some composite products, and the fastener order has to follow. The 3.5 per square foot rule of thumb above belongs to 16 in centers and nothing else: at 12 in it is nearer 4.6.

Buy a box size that leaves you spare rather than one that lands exactly. Stair treads, a picture frame border and the boards you split all come out of the same box, and a second trip costs more than the screws did.

The metal matters more than the head

Where you do get to choose the fastener, the code still constrains what it is made of, and this is the requirement that takes decks apart when it is ignored. IRC R317.3.1 sets out what may touch preservative-treated wood: every fastener and connector touching it, nuts and washers included, is to be stainless steel, silicon bronze, copper, or steel galvanized by the hot-dip zinc process, and a staple in that wood has to be stainless. Ordinary electroplated screws are not on that list.

The exceptions are narrow and worth knowing. A steel bolt of 1/2 in diameter or more is exempt. Anything except nails and timber rivets may instead carry a mechanically deposited zinc coating, at ASTM B695 Class 55 or better. The standard for the hot-dip coating on the fasteners is ASTM A153.

Connectors follow the connector manufacturer's coating recommendation, and where the manufacturer is silent the minimum is galvanized steel to ASTM A653 type G185, or an equivalent. Against the G90 coating on interior hardware, G185 has roughly twice the zinc, which is why a hanger bought off the wrong shelf is a problem you cannot see.

The reason the rule reads this way is a change in the lumber, not in the fasteners. Residential treatment moved off CCA in 2003, and the copper-based replacements, ACQ and copper azole, carry far more copper. Copper in contact with damp steel drives galvanic corrosion, so fasteners that were adequate in CCA stock corrode noticeably faster in the treated lumber sold now.

And do not mix metals in one connection. Putting stainless screws or nails into a galvanized hanger, or the reverse, builds exactly the galvanic cell the coating existed to prevent.

What this guide does not decide

It does not rank fasteners by strength, because the documents behind this site do not publish that comparison and inventing one would be worse than leaving the question open.

It does not reproduce the IRC fastening schedule, so it prints no nail sizes for framing or sheathing. It does not select a joist hanger, size a ledger, or tell you whether a particular structural screw is approved for a particular connection. That last one is answered by the fastener's own evaluation report, which names the connections it is listed for.

And it counts a plain rectangular deck. Mitres, a picture frame border, stairs and openings all change the count, and every one of them changes it upward.

Run the numbers

Frequently asked questions

Are screws or nails stronger?

No document cited on this page publishes that comparison, so this site does not print one. The question the code answers instead is which fastener a given connection is specified with, and where one is named, the other is not an equivalent. For a deck ledger that is a 1/2 in lag screw or bolt; for a joist hanger it is the nail the hanger is rated with.

How many deck screws do I need?

Two per board at every joist crossing. For a 16 by 12 ft deck with 5 1/2 in boards and joists at 16 in on center that is 26 board rows across 13 joists, so 338 crossings and 676 screws. As a quick check at 16 in centers, the deck area in square feet times 3.5 lands within a few percent.

Can I use deck screws in joist hangers?

Not unless the hanger manufacturer lists that specific screw. The published capacity of a hanger was established with a particular fastener at a particular diameter in a particular set of holes, so substituting anything else means the rating no longer describes the connection you built.

Do I have to fill every hole in a joist hanger?

Yes. A partly filled hanger is not at a reduced rating, it is at no published rating, because the tested assembly had every specified hole filled.

Can I use structural screws instead of lag bolts on a deck ledger?

Only under that screw's own evaluation report and its own spacing. IRC Table R507.9.1.3(1) has three fastener columns and all three are a 1/2 in lag screw or a 1/2 in bolt, so the spacings in it do not transfer to a different fastener. Also check footnote d: the tip of a lag screw must fully extend beyond the inside face of the band joist.

What screws can I use on pressure treated wood?

Under IRC R317.3.1, anything touching preservative-treated wood, nuts and washers included, has to be stainless steel, silicon bronze, copper or hot-dip galvanized steel, and any staple has to be stainless. Electroplated screws are not on the list, and mixing stainless and galvanized in one connection creates the corrosion cell the coating was there to stop.

How many screws are in a square foot of decking?

Between 3.36 and 3.61 across every deck size worked out on this page, with 5 1/2 in boards laid 3/16 in apart over 16 in joist centers and two screws per crossing. Move the joists to 12 in centers and it rises to about 4.6, because the joist count is what multiplies every board row.

How many hanger nails does a deck need?

One hanger per joist at each hung end, and every hole in it filled. On a 16 by 12 ft deck with 13 joists hung at the ledger only, that is 13 hangers, and at ten nails each it is 130 nails. Use hanger nails rather than deck screws, and match the metal to the hanger.

Check these numbers yourself

• IRC R317.3, fasteners and connectors in contact with preservative-treated woodUpCodes. The permitted metals, the bolt and mechanically deposited exceptions, and the ASTM A653 G185 floor for connectors. Used because codes.iccsafe.org returns HTTP 403; confirm the edition your jurisdiction enforces.
• IRC Table R507.9.1.3(1) and Section R507.9, deck ledger connectionMassachusetts Residential Code 10th edition, Chapter 5 Floors, reproducing the 2021 IRC. The three fastener columns, footnote d on lag screw tip penetration, the ledger and band joist details and the lateral hold-down capacities. Read 2026-09-07.
• AWC DCA 6, Prescriptive Residential Wood Deck Construction GuidePublished free by the American Wood Council; the IRC deck sections follow this prescriptive guide closely.
• ICC Digital Codes, the IRC itselfPublished by the International Code Council and readable online after registering. Automated access is refused, so the sections above cite reproductions published by jurisdictions.
• ASTM D7032 standard specificationASTM International. The standard IRC R507.2 routes plastic composite decking to, which is why composite joist spacing and fastening come from the manufacturer's instructions rather than a code table.

Figures here last checked against the source documents on 2026-09-16. Codes are amended locally; confirm against the edition your jurisdiction enforces.

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