''AGR ..CULTURE ROC'v
, J
U. S. Department of Agriculture,EForest Servic e
FOREST PRODUCTS LABORATORY
In cooperation with the University of Wisconsi n
MADISON, WISCONSIN
HOUSE FRAMING LUMBE R
SHOULD BE KILN DRIED
By L . V . TEESDALE
Senior Engineer
SCHOOL OF FORESTR Y
OREGON STATE COLLEG E
CORVALLIS, OREGO N
Published i n
SOUTHERN LUMBERMA N
July, 1933
By
l. .
1-
N.
Vas '=
SD
E7
Senior $hgideew
41 should
In the average six room hewer a +
y -foslla
in
• ng .
be enough to coder the diffewence bets the uae of
-initial
lumber or the use of part#a 13r seasoned finning* tit*. lea
coOducte d
cost hae rece it] y hest es=tdtt .ed am the result of experirn
by the Forest ProduOtS LaboraEt .z o a moder e priced ho 4
ly
les'i than the cost of cet-rectLng ,
a *ec•trs o shrin*age .
s eaboaOd joists a ad otbew -s t
members. are used .
tft
s
It has been gene`l practice to coder that air seam
;e
material was satisfactory ft)r strOrtural purposes . Alse 'tl ,t
thoroughly air seasoned material *4s not avai .labie; pawei-rally sesmWNgN
material could be used i.nas nch ai 'e im .derable seasoning would tom .
place during the building opeation,.- In the dwelling studied b y
Forest Products Laboratory, the joist were
A4. ikol.1VO4 hey
ae fir
bad been in the local 1usib .e' yai at Madison, .
during 400
winter, they were only partially seasoned,- tiJA average
tent being in eXce Lse -of 25 percent when delivered . Dulles the bui:l ing
operation-an aplOORWble ant of drying took place ; however, only
-that dryt vgich 0601 rod, 1 efore the plastering
ration proved ti. Sit
•,tiefici - in minir
n. ?1aote.r cracks i
e sulk and plates in the houm. OiecS kiln dried ponderos a
pine and bed an gage moisture content at
t 10 percent when
deliverel . 1°ke
oring was air dries
fah g7eragin g
*out 1 g 'pram'
fire content when !
When all studs and
h fla
tore iti'g isel walls ready
were •
1 in the
top of
laseme ;Losabee OM* la& Wag floor,
qftf
*mows a'b
iTrg
!fig aim*
o exte:
and
y, and
AlINOm !
*Ate
, .and b o
r
were d
.'
arranto measurement') 4awgjbfb Imo made tween e cap
of the,
e a ar _~
se devoping
washer on the floe.*
F
gf"xvf °~
ally
ance between '
_~.
3geolel
hrinamr j► vtqaw
betwee* .
att
llama ! OMNI*
ecord of moisother commend,* 06a'4m xu,:
contac t
pi**, tam two* *No
us tre
and,
brie
the
41ois- HO
elect,
t ime
ture
vs
ote" -'
v
1
4.
M
1009
The bearing partition was sv ipoed . on a steel girder whic h
iilPturn was supped by steel &c .Umns . the studs in both first and
bnd floor start on top of a 2 by 4 inch partition plate . With thi s
arster$ of construction all joist, plateD, caps, and rough floor act a s
supports in the Vertical height of the wall . It is the :age of
these mbaas that constitutes practically all of that fob *Mt the
pipes were measured from time to time. T%e total •cram in dimension
as determine& from each pipe has been plotted on Figure . 1 . The curve
AA on both Figures 1 and 2 represents the average moist e content o f
the joist, plate, sixbfloor, and cap in . the first i'lo icr• A''+ ;), the curve
BB the siim4lar *
is in the second floor unit,
00o joist and
rough floor of the= rti :ie unit.. The net change of ea0h Vie&
determined from the Aktfference in dimensional change bwtween the various
pipes is plotted en 1 , 3r 2. For examples Art esents the shrinkag e
developing to tie fist floor joist, rough floO,rs partition plate, an d
cap as plotted on Figure 2. B represents the sage -members on the second '- '
fi or, =oil the attic j let and floor . The curve C on Fi gRpe 2 was
obtained by datemiring the actual shrinkage as shown on Figure 1 aid
calculating the p'-r
e ,te shrinkage- based on the same amount of woo d
across
the
ac•
s used in A and B . With the various curve s
4PO
Wit*
xI
arable in teXUt of a c it of wood, the cli:ffererree it misture content
e in
imerr iim.ctically all of the e '-f'f
sPn'#
;
Plaster cracks in the house appeared first in a eiw .we'' • •en.
the second floor and later some minor cracks developed in tile bearin g
wall and around the fireplace on the first floor . A . f ,ir Iawoportion of
the shrinkage had taken piaae before cracks d Ee le d as may be noted one
Figures rand 2 . This may be explained by the fait that under ordinar y
-use con itions some shrinkage in the structural frame wean take plac e
without :producing plaster cracks, or in other words there i•s a certain
amount of "take up" or slack between the free ad the meter. Test s
have shown that the gro nd , studs ., doer and wind O* .jambs: ck up moisture from fresh plt,s}t•er, and expand slightly, Subs quent rimer redry.ggh very
ing they shrink an from the plaster and leave a speae e m,
small that will permit some movement of the plaster fheet b eC e contact
is reestablished. After the take up or slack was absorbed > t%R % mus e
under consideration further shrinkage calmed the !racks to e= nd i g
propQx.tian to the slaririage . In spite of the amo . o s li ge fob
MI6* baiises,ira i
s• arid
of shrinkage ire terror of
,,r other defects has not been .important on the first 'l,oe'Gt the second
floor some unsightly cracks have developed . air because of c isren in
the frames of two doors in cross walls, adjustment o the ha teas
been rely so that the doors would latch.
O. igtaZ •hacks did not appear in the first flo ;a~F IMKAI
about 7 percent ~ge in moisture content had taken place i the
'wooden members .
this basis these cracks might •n t'Dave appeared at
Ll if the original moisture content of the members coeposing the first
~•
ii~ii.
Mow than 13 pereenta The figure of 13
R1009
-2-
percent is obtained by adding the 7 percent to 6 percent, which is th e
lowest moisture content found in this unit . Cracks in the second floo r
appeared after about 5 .42 percent moisture change had occurred in th e
first floor units and )4-1/2 percent in the second floor units . On
this basis the first floor joist units should contain less than 11-1/ 2
percent moisture and the second floor less than 12 percent (4-1/2 +
7--1/2) to prevent plaster Cracks on the second floor . In other words ,
if plaster cracks and other shrinkage effects are to be avoided kil n
dried lumber having a moisture content of approximately 12 percent o r
less at the time of installation should be used in house framing .
With joist of low moisture content
is relatively unimportant with the advantage
platform type for interior partitions . For
structuresthe advantage lies wholly with the
of original moisture content .
the method of constructio n
somewhat in favor of th e
bungalows or one-stor y
platform type regardles s
Throughout the greater part of the United States the minimu m
moisture content range of thoroughly air seasoned material is 12 to 1 5
percent, but the average for stock as it comes from the lumber yard i s
generally higher . Stock may be considered well air seasoned and stil l
contain 15 to 17 percent of moisture . Such material will lose ver y
little moisture during the building operation as it is already nearly i n
Equilibrium with the atmospheric condition . Best results will be ob tained by having structural material kiln dried to a moisture conten t
averaging say g to 10 percent . During the building operation such
stock will absorb some moisture from the atmosphere but the average
moisture content will remain appreciably lower than air dried stoc k
under like conditions of exposure . The surface may become wet fro m
rain but such moisture will dry off rapidly during subsequent dr y
weather . Kiln dried joist may not always be available in the loca l
lumber yard, in which event owners and builders should place order s
for kiln dried material with their dealer .
•
. ■
"I'■ 1.
Figure 1 .--Curves showing shrinkage (a) between bash tt
girders and attic floor ; (b) between first
floor partition cap
and
attic floor ; (c) b.
tween second floor partition cap and atti c
floor. The average moisture content of *e
wood
represented in the : first floor, second
floor and attic units is also shown,
7
Shrinkage (inches)
Apr
O
19 3
Ma . y June
_
Dec .
Jan . 193 '.
Feb . I
Max . Apr;_.
May
June
Jul y
Aug .
Sept.
Oct .
Nov.
Dec .
•
Jan. 193
Feb ,
Mar .
Apr._
May _
June
July
Sett .
Oct .
Nov .
Dec .
R1009
si"
-
~~~-
Final coat of pilaster
~
H
J
1
H
O
Vl
O
1-
Plaster, cracks in evidence .
/
-7
Plaster racks in ev Idence on is i
o• r
~-Mil
i
I
~!'
,
'
ME.
_
■_
'
aN
-■ gm _ _
rim s
~■
_■ ____.
____
n __m
°: :
~-
_
1
4,
jois t
2''xg "
2nd floor
jois t
a
■~,
.
1st floo r
jois t
2"x10 rr
.
rearin g partit i on
ho ing po si ti on
of rod s
rams=
•iii__
____►_I__
i.
I_
__=_~i
119
10
.1--BIIWM
•
r
1
Figure 2 .--Curves showing shrinkage (a) between top o f
basement girder and top of first floo r
partition cap ; (b) between top of firs t
floor partition cap and top of second floo r
partition cap; (c) between top of secon d
floor partition cap and attic floor.. The
average moisture content of each unit i s
also show.
0
Apr .
N
0
June_
t
Jul y
Aug .
H
L7l
H
0
_,jilplll
--
ii
Final coat oplaster
El
j
Sept .
Oct :
ter cracks in evid ence ton 2 , • ? - .ar - - -
PI
Nov .
- -- •
N
0
Metal
o May
I-
Moisture content ' (percent )
i,ge (inch)
N l.,.l
Vl
q 0 0 0
(
Plaste
l
crackss in evidenc
on 1st floo
•-
-----
--
Dec ;
1- Jan ,
Feb .
Mar .
11E=
Apr .
May
Jun e
Jul y
Au
g.
1111
Sept,
Oct .
Nov .
Dec.
~
' =BEM
'
=11I=
N Mar .
Feb .
Apr .
May
June
1
Auge
Sept .
Oct t
Nov .
Dec .
11•1
111111•1=11I _
OMEN
~i -1
MIIII s
1E9=111
M
IB M
"I
Mil
11=11
MiU
■i
■ tit
N Jan .
Feb..
Mar . r
Apr .
sm.
P1009
■
r
UN 1
N Jan ,
Jul y
_
n~