It is common
in wood frame and post and beam construction to use multiple pieces of
Dimension Lumber (`2 by’) material, nailed laminated to one another, to make up
posts and columns. Properly fastened
together, typically by nails, but sometimes by bolts, the resulting piece acts
(nearly) the same as a solid wood section of similar dimensions. This article deals with the `properly’
part. The

*National Design Specification for Wood Construction*(NDS), Section 15.3.3, gives us the prescription for nailing the pieces together. I summarize the prescription (rules) as follows:
1. adjacent nails are to be driven from opposite
sides of the post or column;

2. all nails must penetrate all the pieces
(plies, or laminations) and at least three-fourths into the outermost
lamination;

4. nails in a row must be spaced not closer than
20 nail diameters apart and not farther than six times the thickness of the
thinnest of the plies;

5. rows of nails must be spaced between 10 and
20 diameters apart;

6. nails must be located between 5 and 20
diameters from the edges of the column; and

7. two more rows must be provided where the wide
face dimension of the `lams’ exceeds three times the thickness of the thinnest
piece.

To
illustrate the above let’s consider a 3-ply 2 x 6 `column’; and let’s come up
with a nailing pattern for such a column that is 8 feet tall. I will `attack’ these rules in a different order
than given (but one that makes better sense to me).

First, do we
need more than one row of nails (item 5)?
2 x 6 Dimension Lumber is actually 1-1/2 inch (in.) x 5-1/2 in. The 5-1/2 in. wide faces will be nail
laminated to one another. All three pieces
have a thickness of 1-1/2 in., also being the minimum of the three. So, in `formula form’:

... (is) d > 3 t

_{min}? ...
or, in our
case, ... (is) 5-1/2 in. > (3)(1-1/2 in.) = 4-1/2 in.? Yes; we need more than one row of nails. Let’s try

__two rows__.
Second,
let’s come up with the required nail length.
Three plies of 1-1/2 in. each will give a total thickness of 4-1/2
in. The nails must

*be at least long enough*to penetrate three-fourths of the last lam, or,
So, I need
nails that are at least 4-1/8 in. long, ideally about 4-1/2 in. long, and they
can be even longer, but I must then clinch them (pound over the protruding tips).

In `formula form’,

L

_{min}= [(n-1) + 0.75] x t,
n is the
number of plies and t is the thickness of the plies, in this case assumed to
all be the same.

Choosing a
nail size ... the `30d’ common wire nail has a length of 4-1/2 in. and diameter
(D) of 0.207 in. (NDS Table L4).

Perfect!
(with regard to length).

Now to deal
with the end distance:

In formula
form,

or, in our
case, 15 (.207) = 3.1 in. ≤ end distance ≤ 18 (.207) = 3.7 in.

Let’s pick

__end distance = 3-1/2 in.___{min}= 6 x 1.5 in. = 9 in.

Let’s pick

__spacing of nails in a row = 9 in.__
For row
spacing:

... 10 D = 10(.207) = 2.1 in. ≤ row spacing ≤
20 D = 4.1 in.

Let’s

*3 in., and assume only two rows.*__try__
This leaves
us with edge distances of, assuming things centered, ...

5-1/2 – 3 =
2-1/2 ... divided by 2 = 1-1/4 available each edge.

The edge
distance requirement is:

... 5D = 5 (.207) = 1 in. ≤ edge dist. ≤ 20 D
= 4.1 in.

So, yeah,
let’s

__space the rows 3 in. apart and provide at least 1 in. edge distance__. Two rows works perfectly.
Summarizing:

Two rows of
30d common wire nails; 9 in. (max.) o.c. each row, rows spaced 3 in. apart and
not closer than 1.0 in from edges; first and last nails of each row 3-1/2 in.
from ends.

References

National
Design Specification for Wood Construction, American Wood Council, Washington,
D.C.

## 6 comments:

Success is a choice not a dream. So, work hard for it and always be open-minded. Visit my site for more information. Have a good day and keep on moving forward for that success.

triciajoy.com

www.triciajoy.com

The real necklace of a woman is not her looks but her heart. Visit my site for more interesting offer. Thank you and God bless!

n8fan.net

www.n8fan.net

This is great. Thank you for the help.

Post a Comment