xt7h9w08xt5v https://exploreuk.uky.edu/dips/xt7h9w08xt5v/data/mets.xml   Kentucky Agricultural Experiment Station. 1939 journals kaes_circulars_003_335 English Lexington : The Service, 1913-1958. Contact the Special Collections Research Center for information regarding rights and use of this collection. Kentucky Agricultural Experiment Station Circular (Kentucky Agricultural Experiment Station) n. 335 text Circular (Kentucky Agricultural Experiment Station) n. 335 1939 2014 true xt7h9w08xt5v section xt7h9w08xt5v E
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COLLEGE OF AGRICULTURE 1 gf
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Extension Division g 1 ; 1
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THOMAS P. COOPER, Dean and Director 1 i
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CIRCULAR NO. 335 » 1 ; ;
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VENTILATION OF TOBACCO BARNS y 1 1
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  June, 1939 I _;1
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‘ _ Published in connection with the agricultural extension work carried on by coopera- I  
 ‘ UUE cf the College of Agriculture, University of Kentucky, with the U. S. Department of   .1
Agrlculfufc and distributed in furthergmee of the work provided for in the Act of CODQFBSS · ';
Q of May 8, 1914. ,,3
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Circular N0. 335   ,
VENTILATION OF TOBACCO BARNS ,    
S   By RUSSELL A. HUNT and JESSE B. BROOKS 1    
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  ; (jurmg is one ol the most important operations in the produc g A;
   g tim] of tobacco. Successful curing depends largely upon the location ; `    
¥*L° g and Construction of the tobacco barn. ln general a site should be i { 4}
ii     chosen which is thoroly drained and suliiciently removed from other   i I i
  if  buildings to allow free access of air. In erecting a new barn or in f q i  
  ,  repziiring an old one, the important things to be accomplished are i i  
if . .   to construct it as nearly air-tight as possible and to provide a good l    
.1sms _;  system of ventilation. Since there are a suflicient number of barns i I  
z  in Kentucky to care for normal crops, the important problem con- l  
  fronting the tobacco grower at present is to improve existing struc- t i q
at  tures by adding controlled ventilators. Most tobacco barns were  
  built before there was definite information concerning the ventila- _  
 _‘ tion requirements for successful curing; consequently. comparativelv ,
 5 few of them have provision for adequate ventilation in the roof, z i    
 I- such as is shown in the cut on the title page. Controlled ventilation i   ‘  
  is an important feature in providing the best curing conditions. ` i  
'_   The amount of ventilation required for a barn is determined bv i I:
t jg  the location of the structure and the type of tobacco produced. A-\ l y    
    barn located on high ground and fully exposed to the wind and sun ·  
    requires less ventilation than one in a valley or sheltered bv a grove    
    of trees. .~\ barn designed for air cured tobacco, that is for white ‘    
i’   blltlev, one sticker or Green River, needs more ventilation than one i  
  ,   designed for [ire-cured tobacco. lf possible, an air-curing barn  
  should be located on a ridge or hill and entirely in the open where i , ,  
  there is free circulation of air. whereas a hre-curing barn should be S ?j
  ill H grove of trees or valley, sheltered from the wind and Sllll. i  
  THE NEED OF 00NTROLLED VENTILATION    
  The Curing barn should be so constructed and ventilated as to  
@1  PCYIIIII 1`Z1p1d changing of air when needed. The tol>£1CC0 is pi2\C€d    
  ill [IIC barn immediately following cutting, or after wilting, and the  
  (`Ul`l¥l§ lllztv be (j()ntl‘()l]et[ by regtiiztting the venlilzttirlll. \\i2llC1` COIl·  
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Q   sl- Kentucky Extension Circular N0. 335
      stitutes the greater part of the weight of the harvested plant. During ,
    the first stages of curing this water is evaporated from the surface of y
    [l1€ lC3,V€S, 2111(l 0116 of [l1€ most lIl'1PO1`E2`l11[ f3.C[OI`S in Clll`l11g i3 [0 p J
    properly regulate the rate of drying. lf the leaf is dried too rapidly, j
ig `   it is killed prematurely, the curing is stopped and the color of the _
f   leaf remains green. On the other hand, if drying is too slow, the g ]
5   T curing process goes too far, the tobacco either turns a dark red color ·
3   or, possibly, becomes houseburned. The rate of drying of tobacco
    (lCl)C11(lS Lll)O11 Ll1€ l1Ll111lCll[y Zi1](l L€11ll)Cl`3EU1`€ of [lI€ ZllI` 2\llCl. l[S Tilly
E , ol movement thru the barn.
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  ij   Fmums 1. Tobacco barn with insufficient ridge ventilation. .
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l ·   ’ The water content of tobacco at the time of cutting and housing =  
{ ’_..   may range from 75 to 90 percent of the green weight. An acre of i t
    well—ripened tobacco yielding 1,500 pounds of cured leaf weighs ,_vi 1
  ‘``. ifi; when harvested 8 to 12 tons, including the stalks. To cure tobactv if  t
    · successfully, the large amount of water must be removed under such _ t
  ‘·__i_ ~   conditions and at such a rate as best allow the other fundamental   E
  changes to occur in the leaf. Experience has shown that a well· i} c
  ; constructed barn, properly ventilated, provides the means for regu- 2  t
  lating the humidity during the curing period, thru controlled al? _¥
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§_;` ..·_     Mmnons or VENTILATION   C
  Many plans have been devised for ventilating barns. Few half   5
  been Satisfactory under all conditions, The hinged vertical shuU€l`   Z1
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Venlifatirm of T!)b{lL`('() Bar21.s1 5 I 1
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Wing Op side door 10 to 12 inches wide, for each bent, is one of the oldest 1 _
Ce ol and most generally used in Kentucky. lt is effective only when the 1 Q1 »
is to ah- Outside the barn is moving sufficiently to cause some circulation » _ j A
>idly, 1 in the barn. It is entirely ineffective in hot, sultry weather, when { 1 1 2
f the there is little or no air movement. Practically all barns in the areas 1 1
, tht 1 >roducin · air-cured tobacco are e ui ed with this ventilator. 1 i ‘
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    Fxcums 2. An unventilated bam.  
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1 The round, metal, roof ventilator, in general use, improves cur- 1   ,
  ing conditions when used with the side-door or vertical ventilators, , 1 [ 1
1Si11§ Q1 just mentioned. The usefulness of this ventilator depends upon 1 l   .
Fe of   the number placed on the barn and the size of the openings. The 1 *1 Q
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21ghS   most common sizes are the 16" and 20", and a few barns have ven- l ,
  - . . . . . . I
¤HCC0 5,. lllators 24" 1n diameter, The approximate areas oi opening lll ` ¤-
such   the l6", 18" and 20" circular ventilators are 1.4 sq. ft., 1.8 sq. ft. and 1 I i j
im] 1,  2.2 sq. ft., respectively. The common practice is to use only one i   g
W€il· it Circular ventilator to each bent of 12 feet. This amount of Ventllél-   ’
regu-   tion is inadequate unless natural conditions are favorable for curing. { ·
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ia ;g  EXpe1`1ence has rovedthat the rid e ventilator, su lemented it 1
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  by h0Y1ZOntal ound ventilators, is hi hl 1 desirable on barns for 1  
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  Curing all types of tobacco grown in Kentucky. In addition, vertical 1
hill?   $1d€·d0O1‘ ventilators should be provided on air—cu1‘ing bZl1`l1S. Thfiy I  
UUCY   ?U`€ NOK 11eco11m1ended for Fnecuring barns. The ridge ventilator 1  
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g 11 one end of the barn to the other, and when used with the liorizrm.
1   tal ground ventilators and side ventilators in air-curing barns Pm. ;
i   mits satisfactory control of air condition and movement. The ridqt .
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j   8 lvcnlizc/cy EXfC}1.Yf()77 Circular N0. 335  
  i   USE OF VENTILATION C
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i   lt is necessary to use even the best system of ventilation intelli— C
  ‘   gently to obtain good results. The proper operation of the ventila— t 3
{ ‘ ;§ tors and doors varies with the type of tobacco, weather Conditiongy l Y
j Z   stage of curing, and method of curing. ln general, in the early stages i *1
y   of curing, irrespective of type of tobacco, ventilators should be open _ L
I .   when the outside air is warm and there is some movement, and U
  ·'   closed when the outside air is cool, especially if windy.
  , E For burley tobacco, in the early stages of curing, the ventilators i g
5 _   should be open thruout the day and at night, if the air is relativelr _» C
    dry, but closed at night during rainy or foggy weather and also dnr.   Ll
  fil ing the day if the air outside the barn is wetter than that inside,  - ii
l __   Ridge ventilators should always be open when heat is being used   C
    Heat in the barn increases both the evaporation of water from the   H
    tobacco and the movement of air thru the barn; ample ventilation, ‘ C
    therefore, is necessary to permit the moisture-laden air to leave the Q  Li
iQ   barn. When burley tobacco has cured and changed from yellow to  · C
E if 'Ql straw or buff color, the portion of the plant so colored should be dry  i “
Q     enough to rattle. After the plant is thoroly cured, the ventilators  
lr   should be tightly closed to preserve color and quality and prevent j 
i `L damage from wind.  L
  y i The successful curing of iire—cured tobacco requires a relatively   K
  high humidity. Usually bottom and ridge ventilators and doors Z5  |>
    should be open for the hrst two or four days after the barn is hlled.   fi
  4 As soon as fires are started, the ridge ventilators should be closed to   ci
  keep the moisture in the plant for thoro coloring. As soon as the   c<
  'V'` T   leaf is colored, a part of the ridge ventilator may be opened if the Q 
  tobacco gets too high in case. Opening the ridge ventilator a few Q;  tt
  minutes will usually dry the tobacco to a point where it is safe.  Y tl
§ l‘]i;i{ y Since the flow of air thru the barn is regulated by opening the ridge   it
  and bottom ventilators, and by the amount of heat used, it is neces   Cl
  sary to watch the volume of hre and the amount of ventilation   W
  closely during the coloring period. lf the tobacco becomes too high   [J
  in case, the leaf may be dried by keeping the hres constant and   C
ri" ‘._g   opening a part or all of the ridge ventilator for a short time. Oil   U
  the other hand, if the tobacco begins to cure green, fires should be   W
  kept constant or reduced and the ventilators tightly closed to 1‘aiS<‘   h
  Lp humidity. If necessary, water may be sprinkled on the ground, WHUS   fl
—i¥§. .  
i I :.2 
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A l E J
Yi Vcntilrtiion of Tobacco Barns 9 _  
V of the barn, fuel, and even the tobacco itself to restore proper humi-   i
Em   dit); After coloring is complete, it 1S necessary to lower humidity to p l    
.   awicl molding of the stems and to prevent house-burn. Opening I i
ull   ridge yentilators for a short time once or twice daily will suffice, i { ,
On? Ei  After the crop is colored and dried to the point of safety, all ven- i   Q
    tilators should be kept closed. ln smoking dark tobacco, ventila-    
  tors should be ti ‘htly closed to keep in the smoke, , i  
and  Y Dai-}; air-curgd tobacco in general is cured under the same f g `    
[ p   general conditions as fire-cured tobacco. except the use of heat, Since      
    ctiring depends Ll1)'O1l 113.ttl1`L\l. 2111` COll(llll01lS to a large degree, ven- p ~    
dm; In  tilators are highly important lll the process. ln general, the ventila- Q    
_ _,  tors should be operated as described for daik lnecured tobacco. i { i
Udo   In the curing of dark air-cured tobacco, two points stand out. Early- 3 i    
lml   Curgd ci-OPS are generally damaged more or less by houseburn and , i li {
_[h°   molds, while in late-harvested crops some of the leaf frequently  
mn'   cures green. Much of this damage can be prevented by proper ven- i  
the   tilation and proper management during the curing period. Gen- i ’  
W [U  e erally speaking, ventilator doors should be kept open when the ’  
idll  I weather is hot and closed tightly when cool, especially if windy.  
ttors   .‘ 5
vent  `: LOSS OF WEIGHT IN CURING " ` l _  
·°.  2 'l`ests of the loss of weight in curing were made at the \»Vestern    
Lveh  ‘»i   Kentucky Substation at Princeton, with {ire-cured tobacco, in a i i   *
con   barn having both the ridge and horizontal bottom ventilators. The    
lletl.   findings give a general indication as to the rate of loss of water in p  
d to   curing tobacco but they should not be regarded as standard for all  
i the   conditions and crops. i p  
Q the   In each of the five years, 1928 to 1932, inclusive, a few sticks of l _ if  
[ew   tobacco which had just been cut, were immediately weighed and  
sale.   then 1‘e—weighed daily until completely cured. From these weights l  
iclge   it was found that for each hundred pounds of tobacco when freshly Q  
eeesv   tut. seventy-live pounds remained when wilted, fifty-three pounds .. 
ttion   when yellowed, twenty-Eve pounds when colored, and eighteen  
high   |>0t1n(lS when the leaf and stems were dry, but the stalks still green. yi. 
and   O1`, for a single stick of tobacco weighing thirty pounds when cut,  
On   U\’enty—tWo and one-half pounds remained when wilted, sixteen  
cl bc   when yellowed, seven and one-half when colored, and hve and one- _  
raist   half when the leaves and nqidribs were dry. ,~\])l)1`OXl1llZlKCl§' lW0·  
walls   thirds of the original weight was lost by the evaporation of water  
  ,;/{
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l  
_·   lt) Kczzlztr/ry Ifxlcnsion Circzalnr No. 335 r
‘  
    during the first ten days the tobacco was in the barn. This would Y
    mean for each acre of {ire-cured tobacco housed, there would be gm V
      average loss of 800 gallons of water, by the time the leaf was curetl [
    It should be borne in mind that these studies were made with {irc.
it Y   cured tobacco but results obtained also probably apply to dark air- ‘
    i LO35 IN WUGNT U TOBACCO PLANT YKBM W\LTlNG THROUGH CUIUN6 _ i
  [ .00 Av¤zAr.\=. or s vucs rv F:u~a<.\:r¤v·\,•e an when open is held against the bottom cdgc of thc rafters and is pro-   ;
urcd. _ lcctcd from sun zmd rain; (2) the hinges placed at the top edge of V [ 1
A his- ‘ AA   A l lelll A A AA   AA A   A A 1 ¤
{  2 » AA A   »  ifi;    :4  4 2 A A   1 4 A
~ _ 2 1     A 2 A " 2»,_ A 1
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 { ( 4,___   A l A     A   `   ct A 1 )
A  l _ “ i`\ ` " J I  
    wi)   ‘ ( (  
  Fmumz 5. Ridge veiztilzxtor partly open. 4Pl:1xi N0. 1.n 3 1 )‘  
Ei - 1 ‘
»A A Ai 1 l
:~ the door amd under the ventilator roof are protected; (5) the door l 1
 }j vlien closed rests against 21 [lashing board which prevents thc leztk— ’ 1 * j
 * zwc ol ruin and snow under il, the llasliiiws lllZll{lll0` zi tirrht ht re-   l
 ) n L1 b 0 V ( ( 4
  ,2 23% ‘ 1 2:
  A   A A
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  " A. .,.A—   f'! A ~ 2 ` i ¤ A
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  A_   - _   __   AA~- · W_,,,..»·»···" A
 5 4;» ·"‘     A ’-if """ V — A 2 r ' i'
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slum     AAA·   AA»         
 , ·J>.¢'\,¥:; _   __f·:-i}g*";:j# ·      ,   Q:i$?(§;f-‘•?;@‘   t e $; ¥“3:$;; E       ( l,»  _ ¤~   A >—.l_;r  { '4
)lISC(l     A - (  
:`2  FIGURE G. Ridge ventilator being constructed on wooden shingle roof according t0 Plan *4
 {A N0- I. Figure 7. page 12. A I [J
 —&   AA:
{N  i §¤l`lc lcvcrs A IVVA i
A- D h l ' A
and   illlfl door sirinvs are used instead of yullevs and 1`0 ms IO h0l(l thc l i i
  *’ · AA.;
liest.   <>1‘opcn and to close it tight.  
iidlll  EA SU?/1 l. Select the plan, either N0, 1 01* N0. 2, amd study il lllllll  
Sheen 1  ll is understood.  
  1 I=
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M $g I2 lim:/uc/ty Extcnswn Czrcular N0. 335
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2 {     Z;L·I0` on 'L'¤< IZ'. rA¤.s1.   CL
; ri Toaxcizg BARN mock. van n.A 02 MVTWS M0. M oz _
 _ . _1 5°`_m 5"__AT,_`,N,, .::.1 cvs.: evan; npr.; bl
* ' A ¤n..v_ A
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g x 2 Y! _/#' { *~·R_*\\ / xc! WA.:  NQ ` wl
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[   STRAP Hoist $6* No Suuryu mj *5* A /  {
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k ‘ I} _,,#‘” mw bg mv "`   » »_
5 `i " Door: l’L'·0" Long \  _
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{   OFUEINNA RMT;-L  Ggjvum. Rcvns rm:. ·
t     Uxcm \Z'-O' Dun:. .  
if __`.4   yuwu- 7   _.  .
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  A   FQ!. FIq\Jl.LE. 7 AND5, IKUN VE.N’IlLAT'(>\l. OPENINQ FULL LLNQTK of BAKN V ‘   l
—   ‘3.=·A§ t ’t·  H"
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  .. Fmumzs '7 and 8. Tobacco bam ridge ventilator. (Plan N0. 1.)   I
  A   S (
RK   ` T
? ‘_ . `4 
A *  

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1 lag
1 i *1
· ·   l
. Venlilrztiozz of Tobarrr`0 Barns I3 . i
Y J 1
  _ Step 2. Remove the roofing for the width on each side of the l 1
A ridge indicated in the plan. Metal roohng 1nay be cut with a bolt   i
A S cutter, heavy tin snips, shingling hatchet, or an old car spring or [ .
K *  bumper sharpened 0n one edge. lf the metal or composition roohng     Y
‘  V is in good condition after removing, it should be saved for covering y   .
 » one side of the ventilator top. l  
` Step 3. Remove the sheathing. Usually a =l" board is left on y ' l 1  
1  ; Cach side of the ridge; however, they may be removed when build- . § if
. A  ing according to Figure 8, Plan 1. The sheathing is removed to the 5 _    
 N width from the ridge shown in the plan. y l    
 l \"x4`5hc¤{h1¤C]B¤¤fd !`B°'“ R°"°'* A j    
? ‘ \ ¢ r ,
:2    1    
;    Q,.*° ss:. tx 1 l C1
1     »\; w°`i`;:§s§§   l at tl
1   =~—.»ait11¤tj B¤¤rd.s —— i 6"\, X `    
i   · 1  
’  2 1; g
§   Ficmu; 9, Ridge after removal of TUOHHE.   1    
‘“‘1   t . 1 E  
1   Step 4. Build the ventilator. Cut the false rafters for the ven- i {
I   tilator roof 36 inches long. These are cut and nailed together on 1 1 { 2
l   the ground; then raised to the top of the barn with a pulley. Refer 1 ll  
Z ,  to plan for the spacing of the false rafters. A string line should be 1    
i  1- used to line in the ends and ridge of the false rafters. A carpenter’s ,  
 j level is used to plumb the upright ties in Plan 2, Figure 12. ` ` l>  
    S/rj)   After the rafters have been nailed in place, hang the      
1  { door as shown in the plan. For the door, use l—inch boards as wide  
    its the ventilator opening, when building acording to Plan l. The `  
i   door in Plan 2 is made 2 inches wider than the ventilator opening G  
l   iu order to cover the flashing board. The doors are as long as one  
l   bent of the barn, cleated on the inside, and painted on both sides to _ '  
  |)l`C\'Cl1l warping. After hinging the door, the pulleys, levers, door ifgfl
  $|)l`lIlgS, ropes or wires may be connected and tested for ease of  
  <>|>€l`2uion. In Plan 2, place a 2" X ¢l" block at an angle between the  
2:.   UP1`lgl1t rafter ties for the ends of the door to rest Ol'1.  
  $4*6/2 6. Sheathe the ventilator top and cover with wood shin-  
  §l@51 composition, or galvanized rooting.  
  I

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I   I4 1r\·(’}1/[(('/(N li.Y[(’l!.\`I'0}I Cirrzz/ar No. 335 .
2 E2 ,
    Bill of Material for Each 12 Feet of Ridge Ventilator ·
    Note. Where original roofing and sheathing are used to cover the ventilator t0p_ IIIE
¢ I EI amount of sheathing in each bill can be out one-half. This depends upon the kind gf
  >   I material used for rooting.
  _   Items I If built as in Figure 7
  L _   I False rafters 3 pcs. 2** x 10** x 6*-0** i
; ?  I Or 3 pcs. 2** x 12** x 6*-0**
I II Supporting blocks I l pc. 2** x 4** x 6*-0” _ I I
I ~ . I' Ventilator door I 2 pcs. 1** x 10** x 12*-O" .
5 I Or 2 pcs. 1** x 12** x 12*-0**
I   I Ties I 1 pc. 1** x 6** x 12*-0**
I I Cleats I 1 pc. 1** x 4** x 8*-0** 1
I . I Sheathing I 80 Bd. Ft.
    Roonng I 80 sq. Ft.
    Iglhiggei I 3 pr;. 4** galv. strap hinges i I
I I I y pi. ga   swat edawning rope-put E
. . e s, e ** .
‘»   Rope I 16* gf VY; rgpe la j
    Bolts 2 pair screw-eyes or eye-bolts  `
I   Nails (approx.) 2 lbs. 8d, % lb. 6d, and *,4 lb. 10d .
    ___ Items "—ifY“m—M IW If built as in Figure 8 7 _
EX `.=‘ f. False rafters 6 pcs. 2** x 4** x 6*-0** —
I   Supporting blocks I Not necessary  `
K-· .;· Ventilator door 2 pcs. 1** x 10** x 12*-0** “ -·
E ::'  
I.   Or 2 pcs. l" x l2" x 12*-0** _
I . I Ties I 3 pcs. 2** x 4** x 10*-0** pag
I j _ Cleats I 1 pcs. 1** x 4** x 8*-0**  .
I .   I Sheathing I 80 Bd. Ft. ‘
I __ l Roofing 80 Sq. Ft. "