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Beam-building

Beams have long been a part of modern construction, and are a vital part of any home. However there are a few principles worth noting to help you build a top-quality load-bearing system, whether you're a weekend warrior tackling that deck project or a long-time pro.

The critical thing to note is that the best and strongest system does not have any splices (joins) in any part of the beam. Sometimes, that's not feasible: try spanning anything more than 16 feet without a splice!

The key to retaining strength is to put splices in the right spots. Ideally, joins should only be made right over a supporting post.

They can be made elsewhere, but with some limitations. If, as in the example below, there's an eight-foot span between the outside of a beam and a post, then splices can only take place in a space up to one-quarter of the span width distance from the post.

Or, in other words, if you've got an eight-foot span, splices can only be made in the two-foot section nearest to the posts.

Splices are NOT allowed in the remaining 3/4 span between the post and the wall - that's the orange-hued section in the illustration shown here.

We've also included a very small beam table here to help you consider your options. This is by no means exhaustive, and we do ask that you check in with us before beginning any actual work on your project.

 

Beam and Joist Span Tables

Built-Up Wood Floor Beams Supporting One Floor in a House
Maximum Spans for Uniformly Distributed Loads

Species and Grade

Supported
Joist Length

Built Up Beam Size

3-2X8

4-2X8

3-2X10

4-2X10

3-2X12

4-2X12

Douglas Fir #1 & #2

8

9-8

11-2

11-10

13-8

13-8

15-10

10

8-8

10-0

10-7

12-2

12-3

14-2

12

7-11

9-1

9-8

11-2

11-2

12-11

14

7-4

8-5

8-11

10-4

10-4

11-11

16

6-10

7-11

8-4

9-8

9-8

11-2

Hem-Fir #1 & #2

8

10-1

11-7

12-5

14-4

14-4

16-7

10

9-1

10-5

11-1

12-9

12-10

14-10

12

8-3

9-7

10-1

11-8

11-9

13-7

14

7-8

8-10

9-4

10-10

10-10

12-6

16

7-2

8-3

8-9

10-1

10-2

11-9

Spruce-Pine-Fir #1 & #2

8

10-0

11-0

12-10

14-1

14-11

17-2

10

9-4

10-3

11-6

13-1

13-4

15-4

12

8-7

9-8

10-6

12-1

12-2

14-0

14

7-11

9-2

9-8

11-2

11-3

13-0

16

7-5

8-7

9-1

10-6

10-6

12-2

Built-Up Wood Floor Beams Supporting Two Floors in a House
Maximum Spans for Uniformly Distributed Loads

Species and Grade

Supported
Joist Length

Built Up Beam Size

3-2X8

4-2X8

3-2X10

4-2X10

3-2X12

4-2X12

Douglas Fir #1 & #2

8

7-3

8-4

8-10

10-2

10-3

11-10

10

6-6

7-6

7-11

9-2

9-2

10-7

12

5-11

6-10

7-3

8-4

8-4

9-8

14

5-6

6-4

6-8

7-9

7-9

8-11

16

5-1

5-11

6-3

7-3

7-3

8-4

Hem-Fir #1 & #2

8

7-7

8-9

9-3

10-8

10-9

12-5

10

6-9

7-10

8-3

9-7

9-7

11-1

12

6-2

7-2

7-7

8-9

8-9

10-2

14

5-9

6-7

7-0

8-1

8-2

9-5

16

5-4

6-2

6-7

7-7

7-6

8-9

Spruce-Pine-Fir #1 & #2

8

7-10

9-1

9-7

11-1

11-2

12-10

10

7-0

8-1

8-7

9-11

10-0

11-6

12

6-5

7-5

7-10

9-1

9-1

10-6

14

5-11

6-10

7-3

8-5

8-5

9-9

16

5-7

6-5

6-9

7-10

7-11

9-1

Information compiled for your convenience from "The Span Book" Canadian Wood Council 2009 Edition. For expanded options refer to "The Span Book" 2009 Edition.