MiTek Floor Truss Advantages

MiTek Floor Truss Advantages
Using MiTek’s software suite, Open-Web Wood Floor Trusses
are easily created. With SAPPHIRE Structure, the truss manufacturer
can take the builder’s plans….
….from paper….
….to a three-dimensional
virtual jobsite….
….to the real-world jobsite.
Problem areas and solutions can be fixed before the first truss is ever built, saving
the builder time and money in the field, and providing value to the design expertise of
the component manufacturer.
Residential Flooring
Commercial Floors
40 psf TC Live Load
10 psf TC Dead Load (3/4” Plywood Decking)
0 psf BC Live Load
5 psf BC Dead Load (1/2” to 5/8” drywall)
55 psf Total Load
(Concrete Deck)
Commercial
Residential and
Commercial Roofing
(Also Multi-Family Dwellings)
40 psf TC Live Load
25 psf TC Dead Load (1/2” to 2” thick lightweight concrete
cap)
0 psf BC Live Load
10 psf BC Dead Load (1/2” to 5/8” drywall)
75 psf Total Load
50 psf TC Live Load (commercial use)
35 psf TC Dead Load (3” concrete floor)
0 psf BC Live Load
10 psf BC Dead Load
95 psf Total Load
20, 25, 30, 40, 50 psf TC Live Load
(Dependant on local building code requirements)
10 psf TC Dead Load (Includes future re-roofing)
0 psf BC Live Load
10 psf BC Dead Load
40 to 70 psf Total Load (Dependant on TC Live Load)
NOTES:
-Above representative loads are typical loading requirements for many regions in the country. However, the
required applied loading for design purposes is the responsibility of the building designer, within the limitations of
the prevailing local, state, or regional building code specifications.
- Trusses used for roof applications must be checked for local wind loadings.
- Commercial floors may require additional load cases.
Representative Floor Applied Loads
9 – Parallel and Perpendicular
Cantilever Options
9 – Load-Bearing
Cantilever Options
11 – Multiple-Ply
Floor Girders
10 – Variable Floor
Truss Depths
13 – Beam Pockets
9 – Dropped Balcony
Cantilever Options
3 – Built-In
Rim Joist
Options
7 – Max Span
Charts
12 – Stairwell
Opening Framing
2 – Higher End
Reaction
Capabilities
1 - Higher Sheathing
Contact Surface
14 – Field
Trimmable
Options
8 – Versatile
Bearing Options
Details Map
6 - Bracing
4 – Gable
End Options
5 – Open-Web
Advantages
- 4x2 Open-web Floor Trusses offer a wider surface area for attaching floor sheathing.
- More flexibility in the field when setting trusses due to less critical spacing requirements.
- Floor Trusses are more stable during installation, and offer a wider bearing surface for transferring loads.
Larger nailing surface provides
More flexibility for sheathing installation
Wider bearing surface
for more stability
See the chart on the following page for Floor Decking Information.
1a
Open-Web Advantages
Floor Construction
Panel Indent
Thickness
Floor Truss Spacing
Conventional Double-Layer
Plywood Underlayment over
Plywood Sub-Flooring
48/24
40/20
32/16
24/16
23/32”, 3/4”, 7/8”
19/32”, 5/8”, 3/4”, 23/32”
15/32”, 1/2”, 5/8”, 19/32”
7/16”, 15/32”, 1/2”
24” Spacing
19.2” Spacing
16” Spacing
16” Spacing
Wood Strip Flooring over
Plywood Sub-Flooring
(installed at right angles)
32/16
40/20
15/32”, 1/2”, 5/8”, 19/32”
19/32”, 5/8”, 3/4”, 23/32”
24” Spacing
Permitted
1-1/2” to 2” Lightweight
Concrete Cap over Plywood
Subflooring
40/20
19/32”, 5/8”, 3/4”, 23/32”
24” Spacing
Permitted
APA Sturd 1-Floor (must be
Nailed or glued and nailed
According to APA)
24
20
16
32
48
23/32”, 3/4”, 7/8”
19/32”, 5/8”
19/32”, 5/8”
7/8”, 1”
1-1/8”
(Spacing equal to
Panels Indent.)
Panels must either
Be Tongue-andGroove or blocked between
trusses.
APA Glued Floor System
(must be glued according
To APA Spec. AFG-01 and
Nailed)
24” Spacing
19.2” Spacing
16” Spacing
(Available thickness
For either conventional
Subflooring plywood or
For Sturd-I-Floor
Panels.)
- Virtually all decking systems may be easily applied to MiTek floor trusses.
- The wide 3-1/2” nailing surface assures that floor decks are installed accurately and quickly.
- This table is a summary of plywood deck requirements presented by various American Plywood Association
publications.
1b
Floor Decking Information
- Superior end reaction capabilities eliminate the need for additional structural band-board,
web stiffeners, squash blocks or blocking panels.
2
Superior End Reactions
- Floor Trusses feature built-in ribbon notches that can
be built to receive any dimension of lumber desired.
- Continuous ribbons provide stability for installed
trusses, and also provide solid nailing surface for the
edge of floor sheathing.
- Eliminates the need for larger and more expensive
“band-board” solutions required by dimensional lumber
and other engineered wood products.
3
Rim Joist Options
- Gable end floor trusses, sometimes called “ladders”, provide a strong alternative to large
dimensional lumber for parallel closure.
-Gable end trusses are manufactured along with the main span trusses, ensuring matching
height and can include built-in ribbon details.
4
Gable Trusses
- Open webbing provides great benefits to
plumbers and electricians, without the need to
spend time cutting holes in floor members.
- Less cutting reduces jobsite labor and reduces
potentially critical errors that could result in
compromising the structural integrity of the
components.
Maximum Chase Sizes can be seen
on the following page.
PIPES
ROUND
DUCTS
RECTANGULAR
DUCTS
5a
Open-Web Access
Overall
Truss
Depth
(Inches)
Width (W) (Inches)
Diameter
(D)
(Inches)
3”
4”
5”
6”
7”
8”
12
32
25
19
12
6
--
7
13
34
28
23
17
11
5
8
14
36
31
26
20
15
10
9
15
38
33
28
23
19
14
10
16
40
35
31
26
22
17
11
17
41
37
32
28
24
20
12
18
42
38
34
30
26
22
13
19
43
39
36
32
28
25
14
20
44
40
37
33
30
26
15
21
44
41
38
35
31
28
16
22
45
42
39
36
33
30
17
23
46
43
40
37
34
31
18
24
46
43
41
38
35
32
18-1/2
When Height (H) Equals:
TRUSS
DEPTH
5b
Open-Web Maximum Chase Clearances
- Open-web trusses can include interior vertical webs to aid in the attachment of these Strongbacks, and will result in the
individual floor trusses working together as a complete system, helping to transfer loads laterally across the entire floor system,
reducing bounce and vibration as a result.
- 2x6 “Strongback” lateral supports should be located on edge every 10 feet along the floor truss.
- Strongbacks should be securely attached to vertical webs, and it is recommended that when nailing the strongback to the web,
blocking be placed behind the web for support.
- Stongbacks should either be secured to adjacent partition walls or alternate “X”-bridging should be used to terminate the
bracing member.
6
Lateral Bracing
MiTek Floor Truss Max Spans
The chord max-spans shown on the following pages are intended for use in bidding, estimating, and
preliminary design applications. They are presented for six representative floor loadings. For proper
interpretation of these max-spans, note the following:
The max-spans are valid for the following (or better) species grades:
o No. 1 KD Southern Yellow Pine
o No. 1 and better Douglas Fir
o 2100Fb-1.8E Machine Stress Rated (MSR) lumber
o Shorter spans will be achieved using lesser grade 4x2 lumber,
while longer spans are generally possible with higher grade lumber
The max-spans represent truss overall lengths, assuming 3-1/2” bearing at each end. The spans are equally valid for
top chord-bearing and bottom chord-bearing support conditions
The minimum truss span-to-live load deflection is 360 for floor application. For example, the maximum permissible
live load deflection for a 20’ span floor truss is (20 x 12)/360=0.67”
In addition to the consideration of lumber strength and deflection limitations, the maximum truss span-to-depth ratio
is limited to 20 for floor loadings. For example, the maximum span of a floor application truss 15” deep is 15” x 20’ =
300” span = 25’-0” span.
Floor loadings have included 1.00 Load Duration Increase and 1.15 Repetitive Stress Increase
7a
Span Capabilities
40/10/0/5 = 55 PSF @ 0%
40/10/0/10 = 60 PSF @ 0%
50/10/0/10 = 70 PSF @ 0%
Depth
(Inches)
24” o.c.
19.2”
o.c.
16” o.c.
12” o.c.
Depth
(Inches)
24” o.c.
19.2”
o.c.
16” o.c.
12” o.c.
Depth
(Inches)
24” o.c.
19.2”
o.c.
16” o.c.
12” o.c.
12
17-11
20-03
20-06
20-06
12
16-04
18-08
20-06
20-06
12
15-02
17-03
19-02
20-06
13
18-09
21-02
22-02
22-02
13
17-02
19-06
21-08
22-02
13
15-10
18-01
20-00
22-02
14
19-17
22-01
23-11
23-11
14
17-11
20-04
22-07
23-11
14
16-06
18-10
20-11
23-11
15
20-04
22-11
25-03
25-07
15
18-07
21-02
23-06
25-07
15
17-02
19-07
21-09
25-06
16
21-01
23-09
26-02
27-04
16
19-03
21-11
24-04
27-03
16
17-10
20-04
22-06
26-05
17
21-09
24-07
27-01
29-00
17
19-11
22-08
25-02
29-00
17
18-05
21-00
23-03
27-04
18
22-06
25-04
27-11
30-09
18
20-06
23-05
25-11
30-05
18
19-00
21-08
24-00
28-02
20
23-10
26-10
29-07
34-02
20
21-09
24-09
27-06
32-03
20
20-02
22-11
25-05
29-10
22
25-01
28-03
31-02
36-03
22
22-11
26-01
28-11
33-11
22
21-02
24-02
26-09
31-05
24
26-03
29-07
32-07
37-11
24
24-00
27-04
30-04
35-06
24
22-02
25-04
28-01
32-11
- NOTE: Above max-spans are valid for lumber design only.
Plating or other considerations may further limit the truss design.
7b
Span Capabilities
40/25/0/10 = 75 PSF @ 0%
50/20/0/10 = 80 PSF @ 0%
50/35/0/10 = 95 PSF @ 0%
Depth
(Inches)
24” o.c.
19.2”
o.c.
16” o.c.
12” o.c.
Depth
(Inches)
24” o.c.
19.2”
o.c.
16” o.c.
12” o.c.
Depth
(Inches)
24” o.c.
19.2”
o.c.
16” o.c.
12” o.c.
12
14-08
16-08
18-06
20-06
12
13-09
15-08
17-05
20-05
12
13-00
14-10
16-05
19-03
13
15-04
17-06
19-04
22-02
13
14-05
16-05
18-02
21-04
13
13-07
15-06
17-02
20-02
14
16-00
18-02
20-02
23-08
14
15-00
17-01
19-00
22-03
14
14-02
16-02
17-11
21-00
15
16-07
18-11
21-00
24-07
15
15-07
17-09
19-09
23-02
15
14-09
16-10
18-08
21-11
16
17-02
19-07
21-09
25-06
16
16-02
18-05
20-05
23-11
16
15-03
17-05
19-04
22-08
17
17-09
20-03
22-06
26-04
17
16-08
19-00
21-02
24-09
17
15-10
18-00
20-00
23-05
18
18-04
20-11
23-03
27-03
18
17-03
19-08
21-10
25-07
18
16-04
18-07
20-07
24-02
20
19-05
22-02
24-07
28-10
20
18-03
20-10
23-01
27-01
20
17-03
19-08
21-10
25-07
22
20-06
23-04
25-11
30-04
22
19-03
21-11
24-04
28-06
22
18-02
20-09
23-00
26-11
24
21-05
24-05
27-01
31-09
24
20-02
22-11
25-06
29-10
24
19-00
21-09
24-01
28.03
- NOTE: Above max-spans are valid for lumber design only.
Plating or other considerations may further limit the truss design.
7c
Span Capabilities
- Versatile bearing conditions can be manufactured into the open-web floor
trusses to accommodate a variety of conditions.
- Cutting or notching trusses is not required. Trusses can have top-chord
bearing conditions and bearing blocks can be plated into the trusses to
maintain certain heel heights and to match other floor framing material in the
building.
- Fire cut details allow wood floor trusses to be installed in concrete block wall
installations where fire cut conditions are required.
- See the following page for additional bearing conditions.
8a
Versatile Bearing Conditions
Top Chord cut
after installation
Bottom Chord Bearing on
Exterior Frame Wall with
Masonry Fascia Wall
Bottom Chord Bearing on
Exterior Frame or Masonry Wall
Intermediate Bearing – Continuous Floor Truss
(Special Engineering Required)
Header Beam Pocket – Floor Truss Supporting
Header Beam (Special Engineering Required)
Top Chord Bearing
On Frame Wall
Intermediate Bearing
Simple Span Trusses
Intermediate Bearing – Floor Truss Supported
By Steel or Wood Beam
(Special Engineering Required)
Top Chord Bearing
On Masonry Wall
- Versatile bearing conditions can be manufactured into the open-web floor trusses to accommodate a variety of conditions.
- See the following page for additional bearing conditions.
8b
Versatile Bearing Conditions
Extended Top Chord Bearing
(Span Limited by Engineering)
Balcony Cantilever
Extended Top Chord Bearing
(Span Limited by Engineering)
Load-Bearing Wall Cantilever
Dropped Chord Balcony Cantilever
- Versatile bearing conditions can be manufactured into the open-web floor trusses to accommodate a variety of conditions.
8c
Versatile Bearing Conditions
-“Keyed Bearing” or “Shared Bearing” details allow two Floor
Trusses to share the same interior bearing, and eliminates the
need to stagger or overlap the two trusses where possible.
-Sheathing installation is made easier because the supporting
trusses will line up, greatly reducing the need to cut
sheathing at special locations to complete the subfloor
installation.
- The result is a cleaner detail, reduced labor and reduced
material usage.
Top chord bearing truss
rests on end verticals of
lower truss
Bottom chord bearing truss
rests on interior bearing
8d
Versatile Bearing Conditions
- Open-web floor trusses provide superior
cantilever distances. Far greater than EWP
and conventional framing.
- Cantilevers can include built-in details such
as dropped top chords for balcony decking
- Open-Web floor trusses can support greater
concentrated loads to carry bearing walls and
roof loads from above.
The details on the following pages
outline these advantages.
9a
Cantilever Options
- Floor truss cantilevers can support greater concentrated loads at the end of the truss than conventional framing.
See the chart on the following page for a sample of load possibilities.
9b
Load Bearing Cantilevers
Concentrated Load at End of Cantilever (lbs.)
- Floor truss cantilevers often support
load-bearing walls carrying roof live
loads and wall material dead loads.
- This chart provides a convenient
means of determining an equivalent
concentrated load for representative
roof loads which incorporate a 15% load
duration factor for the roof load only.
Roof Load (at 1.15) Plus Wall Load
Roof
Span
(Feet)
20/10/0/10 = 40
psf
30/10/0/10 = 50
psf
40/10/0/10 = 60
psf
20
865
1040
1215
22
965
1125
1320
24
1005
1215
1425
26
1075
1300
1530
28
1145
1385
1630
30
1215
1475
1735
32
1285
1560
1840
Concentrated Load Sample Calculation
Roof Loading = 20/10/0/10 = 40 psf @ 1.15
Roof Load (Roof Truss Reaction) = 40 psf x (30’/2) x 2’-0”o.c. – 1200 lbs.
Wall Load = 8’ Stud Wall Height (@ 85 lbs./lineal ft.) – 85 plf x 2’-0”o.c. = 170 lbs.
Equivalent Floor Truss Load = (1200/1.15) + 170 = 1215 lbs. Concentrated Load
Note: Also check floor truss for dead load only at end of cantilever.
9c
Load Bearing Cantilevers
- Open-Web Floor Trusses can include dropped top chords at balcony locations, which provides builders greater
flexibility when the plans call for exterior decking material.
- Drop distances can be adjusted in 1-1/2” increments to allow for multiple situations.
9d
Dropped Balconies
24” Max.
A
Floor Truss
Jacks
(2) 2x
Rim
Joists
A
Floor Truss
Jacks
Girder Truss
Floor Cantilevered Perpendicular
and Parallel to Floor Truss Span
Girder Truss
Floor Cantilevered Perpendicular
to Floor Truss Span
24” Max.
Approx. 72”
Notes:
-Special engineering required for girder floor trusses.
- Slope for drainage, as required.
- Cantilever span controlled by lumber size and grade
deflection limitations.
Section AA – Floor Truss Jacks
9e
Floor Truss Cantilevers
- Versatile depths allow floor systems to incorporate sunken floor areas into system.
- Walls can be framed at a standard height and “steps” in the floor system can be created by the depths of the floor trusses,
saving the framer time and the builder money.
10
Versatile Floor Depths
- Open-web trusses can be designed as load-bearing Girder Trusses, designed to carry loads from other trusses or wall or roof
loads.
- Multiple-ply trusses can be designed, and are attached in the field with easily installed clips. In some cases, details can be
provided for attachment of truss plies using plywood strips. (Size and location of clips or plywood must be provided by the
engineering department.)
- Open-web truss girders are superior to using large dimensional lumber or engineered wood. In most cases, girder designs can
maintain chase openings and allow duct work and other electrical and plumbing to run through the open webs of the girder
without having to cut the girder and compromise the strength.
- Girder trusses can be designed with beam pockets built in, allowing headers to be inserted through the pockets as needed.
- Trusses can be designed at a lower depth to allow top chord-bearing trusses to rest on top and maintain the same top plane.
11
Multiple Ply Floor Girders
Alternate Ladder
Framing
Stairway Opening
Without Stud Walls
Stairway Opening
With Ladder Framing
Header
Beam
With Strap
Hanger
Stairway Opening
with Bearing Support Walls
Header
Beam
Pocket
Note: Framing opening between header beams must usually be increased beyond
conventional framing opening to permit necessary headroom.
12
Stairway Framing
- Beam “pockets” can be designed into the Floor Trusses to accept various materials inserted
through the webs.
- Trusses can be designed to support load-bearing headers at openings or to carry other floor
trusses. Dimensional lumber can be “threaded through” the webs to create exterior balconies that
run perpendicular to the direction of the floor trusses.
- This versatility allows the builder multiple options for framing today’s complex building designs,
and saves him money on labor and time to complete the required framing.
13
Beam Pockets
Trimmable
End Detail
Firecut
End Detail
16”
16”
4”
Max.
Trim
12”
3-1/2”
MAX.
4”
NAIL TRIMMABLE
END TRUSS TO
PLATE WITH TWO
(2) 16d NAILS
EACH SIDE
Max.
Trim
12”
-Open-Web Floor Trusses can be manufactured with “field-trimmable ends” by utilizing “I-Blocks” that get built into the
ends of the trusses. I-Blocks may be inserted into both ends of a floor truss, allowing the truss to be trimmed up to 24”
total, 12” on each end.
- These I-Blocks feature 2x_ or plywood webs and have top and bottom flanges that are 3-1/2” wide. The I-Blocks are
manufactured at a depth that allows them to be slipped in between the top and bottom chords of the floor trusses and
plated into place in the truss manufacturing equipment.
- The 16” long I-Blocks allow the truss to be cut in the field up to 12” off of the end, allowing for an exact fit in
challenging areas such as angled or irregular walls, curved stairwells and existing construction where exact
measurements may be difficult to obtain prior to truss fabrication.
14
Trimmable End Options