Slate Laps for Varying Pitches

MINIMUM RECOMMENDED LAP FOR DIFFERENT ROOF PITCHES IN MM

 

Normal Exposure Driving Rain Index less than 7m2/s

Severe Exposure Driving Rain Index more than 7m2/s

 

20 deg

22.5 deg

25 deg

30 deg

35 deg

40 deg

45 deg

85 deg

22.5 deg

25 deg

30 deg

35 deg

40 deg

45 deg

85 deg

Princesses

600x350

24x14

115

100

90

75

75

65

65

*

125

100

85

75

75

65

*

Duchesses

600x300

24x12

125

105

90

75

75

65

65

*

135

120

105

90

80

70

*

Small Duchesses

550x300

22x12

130

110

90

75

75

65

65

*

135

115

100

85

75

65

*

Marchioness

550x280

22x11

*

110

90

75

75

65

65

*

120

110

105

85

75

65

*

Wide Countess

500x300

20x12

115

100

90

75

75

65

65

*

120

100

80

75

75

65

*

Countess

500x250

20x10

125

105

90

75

75

65

65

50

130

115

100

90

75

65

65

 

450x300

18x12

*

*

90

75

75

65

65

50

*

*

105

100

75

65

65

Wide Countess

450x250

18x10

*

*

90

75

75

65

65

50

*

*

115

110

90

65

65

Viscountess

450x230

18x9

*

*

100

75

75

65

65

50

*

*

*

105

85

65

65

 

400x300

16x12

*

*

*

75

75

65

65

50

*

*

90

80

75

65

65

Wide Ladies

400x250

16x10

*

*

*

75

75

65

65

50

*

*

95

90

75

65

65

Broad Ladies

400x230

16x9

*

*

*

75

75

65

65

50

*

*

100

105

85

65

65

Ladies

400x200

16x8

*

*

*

75

75

65

65

50

*

*

105

105

90

65

65

Headers

350x250

14x10

*

*

*

75

75

65

65

50

*

*

80

75

75

65

65

Small Ladies

350x200

14x8

*

*

*

75

75

65

65

50

*

*

90

85

75

65

65

Narrow Ladies

350x180

14x7

*

*

*

75

75

65

65

50

*

*

95

90

80

65

65


Slate Sizes and Covering Capacities

 

50mm lap

75mm lap

100mm lap

 

Slate size

mm

Slate size

imperial

No. of slates

Per sq m

Battening

Gauge mm

Battens  required per sq m  in m

Eave slate

Length in mm

Holing gauge mm

No. of slates

Per sq m

Battening

Gauge mm

Battens  required per sq m  in m

Eave slate

Length in mm

Holing gauge mm

No. of slates

Per sq m

Battening

Gauge mm

Battens  required per sq m  in m

Eave slate

Length in mm

Holing gauge mm

Princesses

600x350

24x14

10.2

275

3.64

330

340

10.7

263

3.81

342

353

11.3

250

4

355

365

Duchesses

600x300

24x12

11.9

275

3.64

330

340

12.5

263

3.81

342

353

13.1

250

4

355

365

Small Duchesses

550x300

22x12

13.1

250

4

305

315

13.8

238

4.21

327

328

14.6

225

4.44

330

340

Marchioness

550x280

22x11

14.01

250

4

305

315

14.76

238

4.21

327

328

15.53

225

4.44

330

340

Wide Countess

500x300

20x12

14.6

225

4.44

280

290

15.4

213

4.71

292

303

16.4

200

5

305

315

Countess

500x250

20x10

17.4

225

4.44

280

290

18.5

213

4.71

292

303

19.6

200

5

305

315

 

450x300

18x12

16.4

200

5

255

265

17.5

188

5.33

267

378

18.7

175

5.71

280

290

Wide Countess

450x250

18x10

19.6

200

5

255

265

20.9

188

5.33

267

378

22.4

175

5.71

280

290

Viscountess

450x230

18x9

21.21

200

5

255

265

22.64

188

5.33

267

378

24.15

175

5.71

280

290

 

400x300

16x12

18.52

175

5.71

227

240

19.87

163

6.15

240

253

21.57

150

6.67

252

265

Wide Ladies

400x250

16x10

22.4

175

5.71

227

240

24.1

163

6.15

240

253

26.1

150

6.67

252

265

Broad Ladies

400x230

16x9

24.96

175

5.71

227

240

26.35

163

6.15

240

253

28.6

150

6.67

252

265

Ladies

400x200

16x8

27.9

175

5.71

227

240

30

163

6.15

240

253

32.5

150

6.67

252

265

Headers

350x250

14x10

26.1

150

6.67

202

215

28.5

138

7.27

215

228

31.4

125

8

227

240

Small Ladies

350x200

14x8

32.5

150

6.67

202

215

35.5

138

7.27

215

228

39

125

8

227

240

Narrow Ladies

350x180

14x7

36.55

150

6.67

202

215

39.68

138

7.27

215

228

43.74

125

8

227

240

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