Calculated by the formula: S = U- (Ul/100d).

U = 4,000 lb.

Length. Feet.

6"X6"

7"X7"

8"X8"

9"X9"

10"X10"

11"X11"

12"X12"

13"X13"

14"X14"

16"X16"

8

121

169

225

9

118

165

220

285

10

115

162

216

280

352

11

112

158

214

275

347

425

12

109

155

210

271

342

420

506

13

107

152

204

266

336

414

501

592

14

104

149

202

262

333

410

494

587

685

15

101

145

198

258

327

406

487

580

680

909

16

98

142

194

253

323

400

483

573

672

901

17

96

138

189

250

318

395

477

568

667

893

18

92

184

186

246

314

388

472

563

660

885

19

89

132

183

242

308

384

466

557

652

878

20

86

128

179

237

304

379

460

550

648

870

The strengths of spruce, hemlock, and California redwood are practically the same as in the table.

For white pine, take 7/8 of the above loads.

For white oak, multiply the above loads by 1 1/8.

For Georgia yellow pine, multiply by 1 1/4.

By dividing the values in all cases by the required factor of safety, usually 4, 5, or 6, the safe supporting strength of the column will be obtained.