Selection Of Timbers. The selection of timbers is a matter of great importance in the building of a house.

None should be used which show any signs of decay, or which have a sour or musty smell, as they will in time, unless in a well-ventilated place, affect all wood with which they come in contact.

There should be no large knots nor other defects which weaken the timber to an appreciable extent, and timbers which have the heart in them should not be depended upon to resist heavy strains. This rule generally is followed more closely in small timbers than in those of large dimensions, as it is difficult to obtain timbers of large sizes without heart.

Suggestive Exercises

17. Describe the principal features of a full frame.

18. Describe a half or combination frame.

19. Describe a balloon frame. Compare the three types of frames, and the work upon which they are generally used. What is the chief objection to the balloon frame in a crowded locality?

20. Describe built-up timbers. Compare the efficiency of built and solid timbers.

21. Describe the method of framing the girts into corner posts. What is the objection to cutting mortises into timbers? In which part of the timber does the mortise do the least damage ? In what respect is a balloon frame superior to other forms ? Describe the joints between the corner posts and sills of full, half, and balloon framed buildings. How are ledger boards cut in? From which side of the studs should the depth of the cut be gauged? Why should the ledger be parallel with the outside of the wall ?

22. Describe the use of the steel square in framing a brace. Demonstrate the marking of a shoulder, and the length of a brace. Demonstrate the method of marking the brace cuts in the corner posts and sills, plates, or girts. Between what points is the length of a brace ?

23. Describe the sizing of a floor joist. Why is it necessary? How are floor joists placed if they support a partition ? How is a nailing for the floor boards and ceiling laths secured ? What is the usual distance between the centers of floor joists? How should floor beams which carry headers be treated ? What are floor beams called which extend from a header to the wall ? How should a floor beam which is sprung sideways be straightened? What is the advantage of bridging?

24. What is the usual distance between the centers of studding? Why ? How should studs at angles and openings be set ? How should studding be treated before it is taken to the building? Why? How can a stud in the partition be straightened? Where should the crookedest pieces be used ? What should be done to the studding of a balloon framed house to prevent continuous air spaces ? What other purposes would this serve?

25. How should the floor joists of a porch run? Should a porch floor be laid perfectly level ? Why ? Describe and compare methods of laying porch floors. Should a porch be boarded up tightly underneath the floor ? Why ? Should the porch floor be level with the floor of the house ? Why ? Describe the method of fastening a porch to the house. What should be the height of a porch ? Why not more nor less ? What should be the height of a veranda rail? What is the least rise upon which anything but a metal roof should be used ? How should a metal roof be protected ?

26. Describe a belly rod truss. What is the value of a belly rod fitted in the depth of the girder ? Upon which edge does a timber fail first ? Describe a simple form of trussed girder. Describe a flitch plate girder. Describe a scissors truss, and its advantages. Describe the form and uses of a Howe truss. Why is steel construction supplanting wood for heavy work ?

27. How large should the sills for a moderate-sized dwelling be? the plates? the studs? the stair strings? the floor joists? the rafters? the collar beams ?

28. What imperfections in timber should cause it to be rejected? What imperfections usually have to be permitted in large timbers? Why?