Here are answers to some of the more frequently asked questions about Southern Pine. If you don’t find an answer to your question on our site or in these FAQs, refer to these helpful LINKS.

Southern Pine in Construction

What is Arkansas Pine?

Arkansas Soft Pine was a trade name adopted by that state’s lumber manufacturers in 1916 to promote shortleaf pine (Pinus echinata) of “uniquely superior quality peculiar to the timber growing region in the southern and western areas of Arkansas.” From an old Handbook for Builders (copyright 1955) produced by the now defunct Arkansas Soft Pine Bureau, the differences noted were a softer, more uniform texture, light weight, fine grain and minimum pitch.

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What is Carolina Pine?

Carolina Pine is a trade term generally applied to longleaf pine grown in the rolling sand hills of the Piedmont traversing North and South Carolina, an area located between the coastal plain and the mountain regions.

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What is Dade County Pine?

Dade County Pine is just another name for Florida Pine (see below).

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What is Florida Pine?

South Florida Slash Pine (pinus elliottii var. densa) is a distinct botanical variety of pinus elliottii, or slash pine. It is known to grow only in Florida with a range extending from the Lower Florida Keys to central Florida. South Florida Pine is also known as Dade County Pine. It was used widely in the construction of many historic buildings in the Miami and Key West areas of Dade County, Florida.

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What is heart pine?

Southern Pine lumber is composed of either sapwood or heartwood, or a combination of the two. Heartwood is the “dead” or dormant center of a tree surrounded by the living sapwood. Generally, heartwood can be distinguished from sapwood by its reddish color. Its higher density also makes it harder than sapwood. In the heart pine trade, the rule of thumb is “The redder the better.” Lumber cut from the heartwood of any Southern Pine species can be considered heart pine.

According to the special quality classifications of the Southern Pine Inspection Bureau grading rules, heart-face lumber is free from sapwood on the face side. Heart or all-heart lumber is free from sapwood throughout the piece. However, there is no set ratio of heartwood versus sapwood in the grading rules that defines heart pine lumber. Instead, SPIB rules establish measurement guidelines so the lumber buyer and seller can agree on a specified percentage of heartwood required in each piece.

Of the 10 Southern Pine species, longleaf pine is most commonly referred to in the trade as “heart pine.” It is generally characterized by tighter growth rings, higher density and greater proportion of heartwood. Longleaf lumber is so prized, it merits a special quality classification within the grading rules. However, SPIB adds another wrinkle to the heart pine puzzle. The rule states, “Longleaf lumber shall be produced only from Southern Pine tree species (botanical) of Pinus elliottii [slash pine] and P. Palustris [longleaf pine] …” Because the two species share many characteristics (long needles, higher density), both slash and longleaf timber can be manufactured as longleaf lumber if minimum requirements like ring density are met under the rules.

Because it has a slower rate of growth, longleaf pine was not replanted as widely as other faster growing species. Consequently, longleaf pine may be in short supply while efforts are under way to increase its availability (visit the Longleaf Alliance site to find out more).

Lumber cut exclusively from today’s longleaf timber is also referred to as “new heart pine.” “Antique heart pine” or “reclaimed heart pine” refers to lumber from old growth Southern Pine, regardless of species, salvaged as timbers from old factories, mills or barns, or recovered as “sinker” logs from river bottoms. Other variations on the theme include “old heart” and “river pine.”

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What is Southern Pine (or Southern Yellow Pine)?

According to the handbook Utilization of the Southern Pines, published by the USDA Forest Service, Southern Pine is defined as those species whose major range is in the United States south of the Mason-Dixon line and east of the Great Plains. There are 10 species, all “hard” pines – diploxylon (hard needled) members of the genus Pinus (see chart).

The four principal species – loblolly, shortleaf, longleaf and slash – make up 90% of the Southern Pine timber inventory and are referred to commercially as “Southern Pine” or “Southern Yellow Pine”. “Mixed Southern Pine” includes the minor species of Virginia pine and Pond pine.

The Southern Pines

SpeciesCommon Name
Southern Pine or Southern Yellow Pine
Pinus palustrisLongleaf pine
P. elliotii
P. taeda
P. echinata
Slash pine
Loblolly pine
Shortleaf pine
Minor Species
P. virginiana
P. serotina
P. clausa
P. glabra
P. rigida
P. pungens
Virginia pine
Pond pine
Sand pine
Spruce pine
Pitch pine
Table Mountain pine
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General lumber questions

Can finger-jointed lumber be used in shear wall applications?

Structural finger-jointed lumber can be directly substituted for solid-sawn lumber of the same or weaker species, size and grade for all applications. The most common use is for wall studs. STUD USE ONLY or VERTICAL USE ONLY lumber can be used for studs under dry-use conditions when any bending or tension stresses are of short duration, such as for wind or earthquake loads. That means they can be used in both non-load bearing and load-bearing walls, except where longer-term bending or tension loads are applied, such as with soil loads acting on a permanent wood foundation.

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How many pieces of lumber in a pack?

Southern Pine lumber will be sorted at the mill by width and length before packaging. Each standard unit (or pack, bundle, bunk, lift) contains only pieces of the same width and length, which are stacked in 16 courses, or layers, about four feet wide. The number of pieces per standard lumber pack is: 2×4 = 208 pieces; 2×6 = 128 pieces; 2×8 = 96 pieces; 2×10 = 80 pieces; 2×12 = 64 pieces.

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What is “full sawn” lumber?

According to the reference book Terms of the Trade published by Random Lengths “full sawn” is a term used to describe rough lumber that has been cut to full nominal size. Tolerances above the nominal size are allowed in full sawn lumber, but there is no tolerance for pieces under size at the time of manufacture. With that said, allowances in the Southern Pine Inspection Bureau grading rules for Southern Pine lumber are a bit different. If rough timber is specified, for example, Southern Pine grade rules allow a minimum 3/8-inch scant of nominal size or up to 1-inch oversize. A 6 x 6 nominal timber is 5 1/2 x 5 1/2 actual dressed S4S, or surfaced four sides, but the 6 x 6 rough timber could be sized from 5 5/8 x 5 5/8 up to 7 x 7.

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Why does lumber sometimes warp and crack?

Warp in lumber is any deviation of the face or edge of a board from flatness or any edge that is not at right angles to the adjacent face or edge. Warp can be traced to two causes:
(a) differences between radial, tangential and longitudinal shrinkage in the piece as it dries, or
(b) growth stresses.
Warp is aggravated by irregular or distorted grain and the presence of abnormal types of wood, such as juvenile wood or reaction wood. The six major types of warp are bow, crook, twist, oval, diamond and cup. Splitting and cracking result from the lumber’s reaction to wet and dry moisture cycles. Exposed surface areas expand when wetted by rainfall and contract when dried by the sun. This continual process sets up stresses that can cause cracks and grain separation (checking).

Protecting lumber from the elements with proper coverings during storage and at the building site can help minimize warp and crack. For information pertaining to the protection of decks and porches, please visit

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New Design Values

How can I learn more about the new design values?

New design values for visually graded Southern Pine dimension lumber became effective June 1, 2013. Complete background and other information on this topic can be found here.

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Pressure-treated lumber questions

Can I burn treated lumber?

Wood treated with waterborne preservatives must not be burned because combustion breaks the unique bond formed between the preservative solution and the wood. When this bond is destroyed, the components of the preservative can be released in the form of ash and particulates, which can be harmful if inhaled. For additional information on the proper use and handling of pressure-treated wood products, refer to SFPA’s booklet, Pressure-Treated Southern Pine (download in Publications).

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How long will my pressure-treated posts last in the ground?

Pressure-treated wood that has been properly treated and installed for its intended end-use can be expected to last for many decades. Ongoing tests sponsored and monitored by the USDA Forest Service’s Forest Products Laboratory confirm this finding. Refer to Comparison of Wood Preservatives in Stake Tests – 2011 Progress Report, Research Note FPL-RN-02; prepared by the USDA Forest Products Laboratory.

For complete specification information, please refer to SFPA’s booklet Pressure-Treated Southern Pine (download in Publications).

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What are the design values for pressure-treated Southern Pine?

Reference design values for Southern Pine lumber are tabulated in the Design Values for Wood Construction Supplement of the National Design Specification® (NDS)® published by the American Wood Council. Reference design values for untreated lumber also apply to lumber pressure treated by an approved process and preservative. As a result, new design values that became effective June 1, 2013 also apply to visually graded Southern Pine dimension lumber that is pressure-treated.

Reference design values are based on normal load duration under the moisture service conditions specified; they must be multiplied by applicable adjustment factors to determine adjusted design values. Adjustment factors for untreated lumber also apply to pressure-treated lumber with one exception – in Allowable Stress Design applications allowing an increase with the Load Duration Factor, CD, that factor cannot exceed 1.6 for structural members pressure treated with waterborne preservatives.

For complete specification information, refer to SFPA’s booklet, Pressure-Treated Southern Pine (download in Publications).

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Material Handling and Phytosanitary Compliance

Do phytosanitary rules affect other wood products that I use?

Rules adopted under the United Nation’s International Plant Protection Convention require heat treatment of all non-manufactured (solid sawn) softwoods and hardwoods used in packaging destined for export. By the nature of their production process, manufactured wood products such as plywood, oriented strand board (OSB) and laminated veneer lumber are exempt from the phytosanitary restrictions and are not required to bear an ”HT” mark. However, packaging units made of both non-manufactured and manufactured wood components must still bear an ”HT” audit mark.

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Does Southern Pine meet moisture limits set by the phytosanitary rules?

The phytosanitary rules require that wood for packaging contain less than 20% moisture content at the time of manufacture. To be grade marked, Southern Pine lumber must be kiln dried to a moisture content of 19% or less.

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How does Southern Pine kiln drying compare to minimum HT requirements?

The core temperature of kiln-dried Southern Pine exceeds HT phytosanitary requirements. Typically, kiln schedules for drying Southern Pine exceed 12 hours at 200º Fahrenheit – often higher – thereby far exceeding the core temperature requirement of 56º Centigrade (133º F) for 30 minutes set by the international phytosanitary rules for non-manufactured wood packing material.

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Is Southern Pine suitable for my global material handling needs?

Yes. Southern Pine lumber is kiln dried. Southern Pine’s natural assets – high strength, fastener holding ability and wear resistance – are further embellished in the manufacturing process. Most Southern Pine lumber produced, about 95%, is kiln dried. The kiln-drying process further increases strength and nail holding power, improves stability, results in uniform sizes, and meets the core temperature requirements of international phytosanitary rules.

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What about pressure treatment for phytosanitary use?

Pressure-treated lumber is infused with preservatives to resist insect damage and decay. Although the process results in pest-free lumber, pressure treatment alone will not suffice for the phytosanitary rules. According to regulation, the lumber first must be kiln dried prior to pressure treatment, a standard procedure for HT compliant Southern Pine. Kiln-dried Southern Pine is a preferred wood for pressure treatment because of its ability to achieve deep, uniform penetration of wood preservatives. Pressure treated Southern Pine is also available re-dried, Kiln Dried After Treatment (KDAT).

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What is the standard for heat treatment of Southern Pine lumber?

The Southern Pine Inspection Bureau (SPIB) sets quality standards for Southern Pine manufacturing and grade marking. SPIB defines lumber as being heat treated when “placed in a closed chamber with artificial heat until the lumber achieves a minimum core temperature of 56 degrees Centigrade for a minimum of 30 minutes. The lumber must be in the green condition at the time of heat treatment.”

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Where can I find sources of supply for heat-treated lumber?

Visit SFPA’s Product Locator and select the Material Handling category.

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Outdoor deck tips and other yard projects

What is the maximum span of Southern Pine radius edge decking?

The maximum recommended span for 5/4 Radius Edge Decking (R.E.D.) or Patio Decking manufactured from U.S. grown Southern Pine is 24 inches on center installed perpendicular to the joists. Be aware the maximum recommended span for 5/4 R.E.D. manufactured from imported Southern Pine (stamped I-SP) or Caribbean Pine (I-CARIB) is only 16 inches on center. For more information, visit

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Porch flooring tips and projects

Can I convert a concrete porch to comfortable wood?

HANDY, the member magazine of the Handyman Club of America, demonstrates how to convert a concrete porch into a comfortable, charming wood porch without the labor of removing the concrete. Click here to review the entire process from start to finish.

SFPA’s video program “Southern Pine Porches” is a case study of how a porch is added to the front of a home, replacing a concrete slab.

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Should porch flooring be pressure treated?

To combat the deteriorating effects of outdoor exposure, moisture, decay and termite attack, pressure treatment with a waterborne preservative is recommended for all wood components of a porch. See Building a Porch at

SFPA’s video program “Southern Pine Porches” explains the treating process, porch flooring installation plus proper handling and storage of treated materials at the job site.

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What is the maximum span for Southern Pine porch flooring?

The maximum recommended joist spacing for installing Southern Pine tongue & groove porch flooring is 16 inches on center. See Building a Porch at

SFPA’s video program “Southern Pine Porches” explains the construction process from start to finish.

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Where can I find kiln dried (KDAT) Southern Pine porch flooring?

For best results, Southern Pine porch flooring should be pressure treated and then kiln dried after treatment (KDAT). It is a popular product, available from many local building materials dealers. See SFPA’s Product Locator for a listing of suppliersAlso for more information, refer to Building a Porch at

SFPA’s video program “Southern Pine Porches” explains the porch flooring installation process from start to finish.

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Southern Pine interior flooring

Can you glue down or “float” a Southern Pine wood floor?

We do not recommend gluing down or floating solid-sawn plank wood flooring. To “float” a floor, boards are glued together tongue to groove, but not attached to the subfloor. The only types of wood flooring that should be floated are engineered wood flooring products specifically manufactured for floating. The only solid wood flooring products that should be glued down over the entire installation are parquet, herringbone, and some engineered strip or plank wood flooring. Check with the flooring manufacturer before gluing down or floating any of these types of flooring.

Solid-sawn plank wood flooring should be mechanically fastened using flooring nails or staples. This type of flooring has certain characteristics that make gluing to any surface impractical. First and foremost, the normal shrinkage and swelling cycle that occurs with changes in moisture content (such as seasonal humidity) may weaken and eventually break any glue bond between the planks and sub floor in a glue-down installation or between planks in a floating floor installation. As long as the flooring is not exposed to excessive moisture conditions, mechanical fasteners allow some flexibility in the flooring system, while maintaining a proper attachment of the wood flooring to the subfloor.

Second, if the flooring is glued down over concrete, a proper vapor retarder cannot be installed between the concrete slab and the wood flooring. With solid-sawn strip or plank flooring, exposure to moisture from the concrete may lead to cupping and buckling of the boards. In addition to an unsightly appearance, the cupping and buckling will break the glue bond.

Third, the milling and finishing process itself may leave imperfections in some boards that may make surface-to-surface bonding a problem. The planks may have slight bends, sweeps or crooks that prevent the planks from being properly glued together as required with a floating installation, or prevent the strips from properly adhering to the subfloor as with a glue-down installation.

Fourth, if one is able to install a site-finished, plank floor by using the floating floor method, there are concerns that the flooring will move after installation. Movement of the flooring may result in problems during the sanding and finishing process, such as chatter marks.

The only time glue should be used to install solid-sawn plank flooring is when a single board replacement is being performed. In this case, the flooring contractor may choose to glue down the replacement plank, or to glue and face-nail the replacement plank.

Refer to the guidance in SFPA’s booklet, A Guide to Southern Pine Flooring (download in Publications). Also see the National Wood Flooring Association website for more information. And SFPA’s video program, “Southern Pine Flooring” explains the installation of Southern Pine interior flooring over a concrete slab.

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How do I nail down Southern Pine plank flooring for best performance?

Wood flooring measuring 4 inches and wider is considered plank. Extra care is necessary for good performance of plank floors since wider widths will move more (shrink and swell) with changing conditions. Due to the greater amount of wood per piece, plank flooring has a larger tendency to shrink or swell with a change in moisture content than does more narrow, strip flooring. Therefore, plank flooring has a greater tendency than more narrow, strip flooring to develop a cupped condition should job site moisture levels increase, or to develop gaps between planks and/or checks/splits should job site moisture levels decrease.

This larger tendency for planks to develop a cupped condition and/or gaps can be associated with unwanted up and down movement of planks in the flooring system. To prevent this up and down movement, experienced floor installers recommend that plank flooring be face-nailed as well as following a normal 8″ spaced blind nail schedule over the tongue. We recommend face-nailing with an 8d (2 ½ inch) finish nail (pre-drill pilot holes to avoid splitting) or a 15-gauge finish nail gun.

For plank flooring 4 to 8 inches wide, install two face nails at each butt, spaced about 1½ inch from the butt end and edge. Along the course, one face nail in the center of the plank will work. Nail 16 inches on center over joists, or every 24 inches over a plywood sub floor. A carefully measured and placed string line or light pencil mark (not a chalk line) can be used to mark nail locations.

For plank 10 inches wide, use two nails per plank along the entire course, spacing nails about 1 ¾ inch from the butt and/or edge. For plank 12 inches and wider, we recommend three nails. Countersink nails 1/8 inch and fill before starting the finishing steps.

Before installation of plank or strip flooring, proper acclimation is critical, excess sources of moisture must be identified and eliminated and vapor barriers must be installed to reduce moisture absorption during service. After acclimation and before installation, sealing the back surface of plank flooring may help prevent some cupping normally associated with wider widths: sealing the underside of strip flooring is usually not required. With wider plank flooring, consider leaving a slight expansion crack about the thickness of a putty knife (1/16th inch) between planks.

Refer to SFPA’s booklet, A Guide to Southern Pine Flooring (download in Publications) and the National Wood Flooring Association website for more information. And SFPA’s video program, “Southern Pine Flooring” explains the installation of Southern Pine interior flooring over a concrete slab.

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I have gaps in my pine flooring between the boards. Why?

Some separation or gapping is normal with wood floors. Wood is a hygroscopic material and will absorb or give up moisture with changes in climate. Gaps may appear in wood flooring during dry months and close during the wet season. Even larger gaps may appear in plank flooring due to a greater proportional shrinkage in the wider material. Gaps up to a dime’s thickness are considered acceptable for strip flooring and two dimes is not considered unusual for plank flooring. Maintaining environmental equilibrium year-round is very important to long-term wood floor performance.

NOTE: Extra care is necessary for good performance of plank floors since wider widths will move more (shrink and swell) with changing conditions. Before installation, proper acclimation is critical, excess sources of moisture must be identified and eliminated, and vapor barriers must be installed to reduce moisture absorption during service. After acclimation and before installation, sealing the back surface may help prevent some cupping normally associated with wider widths. Another practice to consider is leaving a slight expansion crack, about the thickness of a putty knife (1/16th inch), between planks. Additional guidance can be found in SFPA’s booklet, A Guide to Southern Pine Flooring (download in Publications). Also, refer to the National Wood Flooring Association‘s website for more information.

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What type of finish should I apply to my Southern Pine floor?

It is recommended that a protective sealer be applied to Southern Pine flooring. There are two types of sealers: penetrating sealers and surface sealers.

Penetrating sealers are floor waxes that prevent penetration of liquids and dirt into flooring. Do not use any floor wax product containing water. Read the wax label carefully to make certain it is suitable for wood floors.

Surface sealers are finishes that do not penetrate the wood-wearing surface, but create a wood-bonding surface layer. Types of surface sealers include polyurethanes, moisture cured urethanes and acid-cured urethanes. Polyurethanes are available in both oil and water-based formulations and offer excellent resistance to wear. Polyurethanes tend to yellow as they age, slightly tinting the floor finish. Moisture-cured urethanes are the hardest of the surface sealers and are extremely prone to finishing errors. Applying these under the supervision of an experienced floor-finishing professional is recommended. Acid-cured urethanes, also known as ”Swedish-finishes” provide a clearer and somewhat harder surface than polyurethanes.

Due to the technical nature of the application of such finishes, we recommend consulting a floor-finishing expert. Refer to the guidance in A Guide to Southern Pine Flooring (download in Publications). Also see the National Wood Flooring Association website for more information. More flooring tips are presented in SFPA’s video program “Southern Pine Flooring”.

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Where can I find replacement boards for an old wood floor?

Lumber sizes were reduced by 1/8 inch in width and thickness during the 1970s, so the dimensions of pattern stock, such as flooring, cut from this lumber have also been reduced proportionally by 1/8th. Today, standard patterns of Southern Pine strip flooring (strip is anything under 4”) are cut in widths of 1 1/8, 2 1/8 or 3 1/8 inches on the face (less the tongue and groove). As a result, it may take some detective work to get what you need. You may be able to find a mill capable of producing a custom run, but it will be costly. Furthermore, if the flooring is heart pine, you will probably need to find some antique heart pine flooring for a genuine match, or to at least match color, experiment with stains. You will also need to specify flat grain or vertical grain. You may be able to find some heart pine boards and have a local custom millwork shop run them to pattern. Try the product database at for a start.

Another idea would be to replace all damaged boards in the visible living areas with good boards taken (carefully!) out of smaller rooms or closets (solves the color match and sizing problem), then install new flooring (stained to match) where the old was removed.

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Does building with wood products harm the environment?

No. Building with wood products actually helps the environment by mitigating climate change. Wood products have attributes that contribute to a healthy environment, such as the ability to store carbon while being formed naturally as trees and during their service life as building products. Scientists have reported that removing carbon from the atmosphere is one of the most significant ways to reduce the negative impacts of climate change. Wood products also require less energy to manufacture, transport, construct, and maintain than other building materials such as steel and concrete. Using wood products from sustainably managed forests ensures the growth of potential carbon storage through our forests and wood products.

More information on the environmental benefits of building with wood can be found here.   Also, visit Think Wood.

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What does the “d” in certain nail sizes mean?

Our friends at Maze Nails explain that the ”d” abbreviation for ‘penny’ is of ancient origin, representing the first letter of the Roman coin denarius.

There are two possible explanations for the English ‘penny’ system of designating nail lengths. One is that the eight-penny, six-penny, two-penny nails, etc. were so-called originally because 100 nails cost eightpence, sixpence, twopence, etc. The other theory says that 1,000 eight penny nails, for example, weighed eight pounds, 1,000 four penny nails weighed four pounds, etc.

Nails used for wood-to-wood applications (such as framing nails, wood siding and shingle nails, etc.) are traditionally referred to by the penny designation, i.e., 5d or 6d nails, etc. However, nails for non-wood applications are primarily referred to by inches, i.e., 1½-inch or 2-inch nails, etc. There is no readily apparent system correlating the various penny designations. They must be memorized individually. See the penny-to-inch nail conversion chart.

Penny-inch Nail Eqiuvalents
2d = 1"
3d = 1¼"
4d = 1½"
5d = 1¾"
6d = 2"
7d = 2¼"
8d = 2½"
9d = 2¾"
10d = 3"
12d = 3¼"
16d = 3½"
20d = 4"
30d = 4½"
40d = 5"
50d = 5½"
60d = 6"
70d = 7"
80d = 8"
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