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Materials for dump. proofing
Timber.
BUILDING (CONSTRUCTION) REGULATIONS, 1956
20. Materials for damp-proofing shall consist of— (a) sheet lead or sheet copper;
(b) asphalt;
(c) self finished bitumen impregnated felt laid in bitumen; (d) a core of sheet lead and bituminized hessian cloth be- tween two layers or coats of bitumen surfaced with tale or other suitable material;
(c) a core of sheer lead between two layers of bituminized felt fibre coated with bitumen and surfaced with talc or other suitable material; or
(/) any other suitable material or combination of materials; and shall be such as the Building Authority may approve as being durable, impervious to moisture and in all other respects suitable for their purpose, having regard to the particular circumstances of the case.
21. Structural timber shall be of a quality and strength suf- ficient for its purpose and shall be well seasoned, sound and free from knots or shakes in such quantity as to affect adversely the strength or durability of the timber.
PART III. Loads.
BUILDING (CONSTRUCTION) REGULATIONS, 1956
(3) In calculating the stability of the building as a whole. the following additional horizontal forces shall be taken into
account-
(a) the horizontal components of the windloads on roofs as specified in Table VII considered as acting halfway up the roof;
(b) the forces due to winddrag, calculated as the plan area
in square feet of the roof multiplied by-
(Q) a force equal to 0.05 P where the wind is at right angles to the slope of the roof,
(ii) a force equal to 0.025 P where the wind is parallel to the slope of the roof.
TABLE VJ,
Basic wind pressure—(P).
Wind pressure P. (lbs. per square foot) *
Effective height of building.
Exposure A V=90 m.p.k.
Exposure R. V=105 m.e.h.
Exposure C.
V=120 m.ph.
up to 10
18
2.1
32
20
21
22
28
30
23
$2
42
40
36
45
50
37
48
60
28
39
61
80
1:0
งา
64
100
43
97
45
50
140
160
180
200
or more.
47
63
49
61
07
52
49
Wind uffecta.
22. (1) Every building shall be constructed so as to be capable safely of sustaining, resisting and transmitting, in addition to the dead and imposed loads, and without exceeding the appropriate limitations of permissible stresses, all forces due to wind pressures in any horizontal direction of the intensities specified in Table VI for the height of the building and exposure of its site.
(2) Such forces shalt be calculated-
(a) for the vertical surfaces of the building, at the basic pressure (P) in Table VI appropriate to a height measured from the general ground level up to halfway between the caves and ridge levels of the roof, considered as acting uniformly on the full height of the vertical walls; (b) for any projections above the roof, at the basic pressure (P) in Table VI appropriate to the height from the general ground level to the top of such projections, considered as acting uniformly on the whole projected area of the pro- jection,
120
* For intermediate values of height, the pressures shall be calculated by
interpolation.
↑ The degrees of exposure are:--
Exposure A.
Exposure R.
Thia exposure covers open country not directly exposeł to the full effect of typhoons, not more than 200 ft. above sea level, and not on the sea front.
This exposure shall be used for exposed aites not more than 200 ft. above sea level and not on the sea front. and for sheltered sites from 200 to 800 ft. above sea level. It is the minimum exposure for all bulldings more than 80 ft. high.
Exposure C. This exposure is applicable to exposed sites open to and near the sen, and to sites more than 800 ft. above sea level.
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