[CCMC 13677-R] CCMC Canadian code compliance evaluation

It is the opinion of the Canadian Construction Materials Centre that the evaluated products, when used as fasteners for structural lumber connections in accordance with the conditions and limitations stated in this evaluation, comply with the following code:

National Building Code of Canada 2015

The above opinion(s) is/are based on the evaluation by the CCMC of technical evidence provided by the evaluation holder, and is bound by the stated conditions and limitations. For the benefit of the user, a summary of the technical information that forms the basis of this evaluation has been included.

Product names

• SWG ASSY® 3.0 Self-Tapping Wood Screws
• SWG ASSY® VG Plus

Product description

The products are self-tapping screws (STS) that are available in many combinations of diameters, lengths, head types, thread types (single, double or coarse threads), and as partial-thread screws or full-thread screws. This evaluation covers the following 5 specific designations of proprietary SWG ASSY^® Self-Tapping Wood Screws made from carbon steel (see section Self-Tapping Screws - Specification Summary for a summary of the screw specifications):

1. three (3) partial-thread screws with self-tapping tip: SWG ASSY^® 3.0 SK, SWG ASSY^® 3.0 Kombi, SWG ASSY^® 3.0 Ecofast, and
2. two (2) full-thread screws with self-drilling tip: SWG ASSY^® VG plus CYL (cylinder head), SWG ASSY^® VG plus CSK (countersunk head).

The SWG ASSY^® 3.0 Self-Tapping Wood Screws are self-tapping while the SWG ASSY^® VG plus ones have a self-drilling tip, which is also self-tapping. The partial-thread screws have a coarse thread while the full-thread screws have a single thread. Additional specifications and detailed information are available from the manufacturer’s Design Guide outlined below.

Installation description

General note: The use of the term "embedment depth" throughout this Evaluation Report is equivalent to "penetration length" of the self-tapping screw into the wood member.

Angle of installation

The products have been evaluated for installation at 3 angles in relation to the timber members being fastened together: 30°, 45° and 90°.

Spacing

The screw spacings outlined below originate from the European approval for SWG ASSY^® Self-Tapping Wood Screws and the German standard DIN 1052.

Installation practice

For a successful installation, all aspects of the manufacturer’s screw installation instructions must be followed, including requirements for the drill bit, drill specification, torque, screw guide for angle installations, steel plate details, etc.

Manufacturing plant

This evaluation is valid only for products produced at the following plant:

Product evaluated by the CCMC Indicates that the product from this manufacturing facility has been evaluated by the CCMC

The CCMC’s compliance opinion is bound by this product being used in accordance with the conditions and limitations set out below.

The products are self-tapping wood screws for structural wood connections fabricated with dry lumber, intended to be used as fasteners for structural lumber connections for dry service use ^{Footnote (1)} applications only.

The following list of conditions and limitations apply to this product evaluation:

• The structural wood design, with proprietary fastener design values herein, is to be in accordance with CSA O86-14 performed by a professional engineer, with an expertise in wood design, licensed to practice within the Provincial/Territorial jurisdiction.
• The published resistances are limited to Canadian wood species/densities and proprietary structural composite lumber (SCL) tested and outlined below.
• For the withdrawal applications:
  • The lumber side plate member, being connected to the main member, must have a minimum thickness of 4d (where d is the thread outer diameter). At the admissible installation angles of 30° to 90° (angle from the horizontal (parallel to grain)), the following exceptions apply:
    1. for the screw diameters ≥ 10 mm and installation angles other than 90° (i.e., perpendicular to grain) the minimum wood member thickness (side and main) is 8d;
    2. for the screw diameters = 12 mm and installation angles other than 90° (i.e., perpendicular to grain) the minimum wood member thickness (side and main) is 10d.
  • The withdrawal resistance has an upper limit set by the tensile capacity of the screws and must not be exceeded. See table "Strength of SWG ASSY^® screws made from carbon steel" below for the prescribed tensile capacities and limiting factored tensile values for the 6-mm, 8-mm, 10-mm and 12-mm screws. (The section Application Cases Permitted outlines permitted application cases in tabular form.)
• For lateral load resistance, the minimum wood side and main member thickness for the self-tapping screws shall be 50 mm for d < 10 mm and 100 mm for d ≥ 10 mm in order to avoid mode 1 and mode 2 failures in wood so that a ductile steel yielding mode can be achieved.
• This evaluation does not apply to connections with other materials (i.e., panel products).
• The screw angles, spacings, end/edge distances and end-grain (at angle) installations must follow the prescribed requirements and the manufacturer’s recommendations.
• The Service Condition Factor for lag screws applies to these self-tapping screws and is limited to the connections fabricated with seasoned lumber and used in dry service.
• Surface coated screws are not evaluated for applications where corrosion resistance is required, and can't be used in preservative treated wood.
• Other limitations are applicable as outlined below for specific applications.

The installation of the products must be in accordance with the manufacturer’s details found in the “Design Guide for ASSY^® Screws in Canada,” Version 1, October 2013.

The manufacturer, SWG/Würth, provides engineering and technical support through My-Ti-Con Ltd. in conjunction with the “Design Guide for ASSY^® Screws in Canada” and offers the following contact number:

• MY-TI-CON: 866-899-4090 or info@my-ti-con.com

This evaluation is based on demonstrated conformance with the following criteria:

The Report Holder has submitted technical documentation for the CCMC’s evaluation. Testing was conducted at laboratories recognized by the CCMC. The corresponding technical evidence for this product is summarized below.

Material requirements

The CCMC’s Technical Guide for self-tapping wood screws sets out the nature of the technical evidence required by the CCMC to enable it to evaluate a product as an acceptable or alternative solution in compliance with the NBC 2015. The Report Holder has submitted test results for the CCMC’s evaluation. Testing was conducted by an independent testing agency recognized by the CCMC. The corresponding results of the tests conducted for the products are summarized in the section Summary of Testing and Design Value Derivation.

Characteristic densities

The products’ qualification test program and pre-engineered tables in the following sections of this Report are based on the following species and respective oven-dry relative densities.

Table 1. Oven-dry relative densities of timber species

Timber densities
Visually graded lumber	Glue-laminated timber	Mean oven-dry relative density
D fir-L	D fir-L	0.49
S-P-F	–	0.42
–	S-P-F	0.44
Hem-fir	Hem-fir	0.46
Northern	–	0.35
S-Y-P	–	0.55
Structural composite lumber (SCL) density
Parallam® (PSL)		0.50

Characteristic screw fastener dimensions and strengths

Dimensions

The detailed dimensions and thread lengths of the STS are outlined in the section Detailed Screw Dimensions.

Note

Self-tapping screws have an “outside” screw diameter that exceeds the shank diameter. In conventional lag screws, the outside screw diameter is typically equal to or less than the shank diameter, unless the lag screw is a “reduced body diameter” lag screw, in which case the shank diameter is also less than the outside screw diameter.

Table 2. Strength of "SWG ASSY®" screws made from carbon steel

Partial- (PT) or full-thread (FT)	“SWG ASSY®” type STS	Outside thread diameter (mm)	Root diameterTable footnote (1) (dmin, mm)	Bending yield strengthTable footnote (2) (MPa)	Screw tension strength (kN)		Unfactored screw shear strengthTable footnote (2) (MPa)
					Unfactored resistance	Factored resistanceTable footnote (2)
FT	VG CYL	6	3.8	969	11.3	9.04	578
PT	SK, Ecofast		3.9
FT	VG CYL, VG CSK	8	5	1015	18.9	15.12	641
PT	SK, Ecofast, Kombi		5.3
FT	VG CYL, VG CSK	10	6.2	942	24	19.2	691
PT	SK, Ecofast, Kombi		5.3
FT	VG CSK	12	7.1	1147	30	24	536
PT	SK, Kombi		7.2

 

Spacing of "SWG ASSY^®" screws in timber

The minimum spacing, end and edge distances of the products loaded laterally (i.e., shear) or axially (i.e., withdrawal) in timber must follow the principles of the German standards DIN 1052 and Dibt ETA-11/0190. The screw spacing and end/edge distances are summarized in Figure 1 and the "Minimum spacing, end and edge distances for the SWG ASSY^®" tables below for information only; the designer must consult the manufacturer’s Design Guide for accuracy and additional information.

Minimum spacing, end and edge distances ^{Footnote (1)} for the SWG ASSY^® self-tapping wood screws – screw types (d = outside diameter) screws loaded laterally

Minimum spacing or distance	Partial-thread self-tapping
	SWG ASSY® 3.0 SK, Kombi, Ecofast
	Relative density ≤ 0.42	0.42 < relative density ≤ 0.50 kg/m3
Spacing parallel to grain (SP)	12d	15d (22.5d in D-fir)
Spacing perpendicular to grain (SQ)	5d	7d
Loaded end distance (aL)	15d	20d (30d in D-fir)
Unloaded end distance (a)	10d	15d (22.5d in D-fir)
Loaded edge distance (eL)	10d	12d
Unloaded edge distance (e)	5d	7d

 

Minimum spacing, end and edge distances ^{Footnote (1)} for the SWG ASSY^® self-tapping wood screws – screw types (d = outside diameter) screws loaded laterally

Minimum spacing or distance	Full-thread self-drilling + self-tapping
	SWG ASSY® VG plus CYL, SWG ASSY® VG plus CSK
	Relative density ≤ 0.50 kg/m3
Spacing parallel to grain (SP)	5d (7.5d in D-fir)
Spacing perpendicular to grain (SQ)	3d
Loaded end distance (aL)	12d (18d in D-fir)
Unloaded end distance (a)	7d (10.5d in D-fir)
Loaded edge distance (eL)	7d
Unloaded edge distance (e)	3d

 

Minimum spacing, end and edge distances^{Footnote (1)} for the SWG ASSY^® self-tapping wood screws – screw Types (d = outside diameter) screws loaded axially

Minimum spacing or distance	Full-thread self-drilling + self-tapping
	SWG ASSY® VG plus CYL, SWG ASSY® VG plus CSK
Spacing parallel to grain (SP)	5d (7.5d in D-fir)
Spacing perpendicular to grain (SQ)	2.5d
Loaded end distance (aL)	5d (7.5d in D-fir)
Unloaded end distance (a)	–
Loaded edge distance (eL)	3d
Unloaded edge distance (e)	–

 

Factored withdrawal resistances

Table 10. Factored withdrawal resistance per 20-mm thread embedment depth^{Table footnote footnote (1)}

Factored withdrawal resistance Prw,∝ per 20 mm (¾ in.) of thread penetration									Factored tensile resistance in kN
∝ (°)	d (mm)	ρ = 0.35	ρ = 0.42	ρ = 0.44	ρ = 0.46	ρ = 0.49	ρ = 0.5 PSL	ρ = 0.55
90	6	0.63	0.91	0.97	1.06	1.20	0.70	1.51	9.04
	8	0.85	1.22	1.29	1.41	1.60	0.94	2.02	15.12
	10	1.06	1.52	1.61	1.76	2.00	1.17	2.52	19.2
	12	1.27	1.83	1.94	2.12	2.40	1.41	3.02	24
45	6	0.54	0.78	0.83	0.91	1.03	0.60	1.30	9.04
	8	0.73	1.04	1.11	1.21	1.37	0.80	1.73	15.12
	10	0.91	1.31	1.38	1.51	1.71	1.00	2.16	19.2
	12	1.09	1.57	1.66	1.81	2.06	1.21	2.59	24
30	6	0.51	0.73	0.77	0.85	0.96	0.56	1.21	9.04
	8	0.68	0.98	1.03	1.13	1.28	0.75	1.61	15.12
	10	0.85	1.22	1.29	1.41	1.60	0.94	2.02	19.2
	12	1.02	1.46	1.55	1.69	1.92	1.12	2.42	24