1. Wood Framing November 30, 2016 INTRODUCTION TO ARCHITECTURAL MATERIALS
INSTRUCTOR:
JOHN D CHILDS
Wood
Framing
November 30, 2016

2. Timber or Braced Framing Medieval Tradition Carried into 19th Century
INSTRUCTOR:
JOHN D CHILDS
INTRODUCTION TO ARCHITECTURAL MATERIALS
Timber or Braced Framing
Medieval Tradition Carried into 19th Century

3. Hewing with broad axe and adze
Wood is hewn green
Oak or pine

4. Secondary members (floor joists, common rafters) are sawn, either in a sawmill or with a pitsaw.

5. Timber Framing: Joints
INSTRUCTOR:
JOHN D CHILDS
INTRODUCTION TO ARCHITECTURAL MATERIALS
Timber Framing: Joints

6. Joints are cut and joined with axe, adze, chisel , slick, auger

7. Framing joinery must resist force in at least one of these directions:
Compression
Tension
Shear

8. Strength in wood: Varies with direction and type of stress
Tensile Strength Parallel to Grain: Strongest
Compression Parallel to Grain

9. Compression Perpendicular to Grain
Tension Perpendicular to Grain: Weakest

10. Bending Strength (Modulus of Elasticity, E)
Breaking Strength (Modulus of Rupture, MR)

12. Mortise and Tenon joints hold main framing elements together
Plain
Open
English Tying Joint
Shouldered
Housed
Tusk

13. Lap joints attach crossing members
Shouldered dovetail
Dovetail
Half lap
Lap joints attach crossing members
Dovetails attach members in tension
Full lap
Angled dovetail

14. Scarf joints attach
framing members end-to-end

15. Pegs hold joints together
Must be thick enough to resist shearing. Tight fit aids in this
Must not be so thick that they diminish strength of joint

16. Timber Framing: Principle Elements
INSTRUCTOR:
JOHN D CHILDS
INTRODUCTION TO ARCHITECTURAL MATERIALS
Timber Framing: Principle Elements

17. Strength Considerations in Framing
Compression
Shear

18. Tension Crack at Mortise in Diagonal Grain Timber

19. If beam is long enough, dead weight (weight of beam) will exceed modulus of rupture.
Truss structures solve problem of crossing increased spans.

23. Bents use trusses to add strength
Trusses use diagonal members to add strength in all directions. Truss joints must be able to hold in tension as well as compression.
Trusses add strength, allowing thinner members to be used.
Trusses allow beams (girts, plates) to span greater distances.
We will see later that trusses make it possible to build an entire house with 2 x 4 lumber

24. Raising Bents

26. Post
Tension Brace
Sill
Post
Knee Brace
Girt

27. Joists
Summer Beam
Jackson House, Portsmouth, NH (Historic New England)

28. Tension Brace Rafter Purlin
Jackson House, Portsmouth, NH (Historic New England)
Pierce House, Dorchester, MA (Historic New England)

29. Interior Wall Coverings
INSTRUCTOR:
JOHN D CHILDS
INTRODUCTION TO ARCHITECTURAL MATERIALS
Interior Wall Coverings

30. Lath and Plaster Jackson House, Portsmouth, NH (Historic New England)
Pierce House, Dorchester, MA (Historic New England)
Lath and Plaster

31. Paneling
Wainscot

32. Paneling mitigates effects of expansion and contraction of wood

33. Floors INSTRUCTOR: JOHN D CHILDS
INTRODUCTION TO ARCHITECTURAL MATERIALS
Floors

34. Wide pine boards
Narrow oak boards
Wide oak boards
Tongue and groove joint

35. Parquet floors mitigate effects of expansion and contraction of many parallel boards

36. Stairs INSTRUCTOR: JOHN D CHILDS
INTRODUCTION TO ARCHITECTURAL MATERIALS
Stairs

37. 17th C.
18th C.
19th C.
20th C.

38. Exterior Siding INSTRUCTOR: JOHN D CHILDS
INTRODUCTION TO ARCHITECTURAL MATERIALS
Exterior Siding

39. Clapboard: 17th & 18th C. – riven, 19th & 20th C. - sawn
Board siding – sawn Shingles: 17th & 18th C. – riven, 19th & 20th C. riven or sawn

40. Nail History:
Wrought nails
Cut nails
Wire nails

41. Log Cabins: Construction technique introduced by Swedish immigrants in the Delaware Valley in the 17th C.
Does not appear in New York or New England until mid 18th C.

42. Balloon Frame Construction:
Introduced in U.S.
by G. W. Snow, Chicago, 1832

44. Uses dimensioned lumber (2x4’s)
on 16” centers. Wall studs extend full
height of building. 2nd floor joists rest
on ledger nailed into mortises cut in studs

45. Balloon frames do not offer fire breaks between floors

46. Platform or Western Framing:
20th Century
Platform frames offer fire breaks, and allow use of standard length lumber.

47. Truss Framing:
20th Century truss frames allow use of standard 2 x4 dimensioned lumber for all structural elements.