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Rothoblaas

VGZ · Fully threaded cylindrical head screw

Name: VGZ · Fully threaded cylindrical head screw
Brand: Rothoblaas
SKU: VGZ780

Product code: VGZ780

£18.00 ex VAT · 50 per box

£21.60 inc VAT

£0.36 per unit

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VGZ is a fully threaded structural screw with a cylindrical head, in electrogalvanised carbon steel. It is approved for structural applications subject to stresses in any direction to the grain, from 0 to 90 degrees.

The cylindrical head is the point of it. It lets the screw penetrate and pass through the surface of the timber rather than stopping on it, so the fixing goes away inside the member. That is what makes VGZ a reinforcement and coupling screw rather than a surface fastener, and it is why it suits concealed joints, timber couplings and structural reinforcement.

Where it's used

Reinforcement orthogonal to the grain, for hanging load where a secondary beam meets a main beam
Side-by-side joining of CLT floors, which the datasheet describes as very high stiffness
Coupling beams, in structural renovation and in new work
Joining small timber elements, such as the crossbeams and uprights of light frame structures
Installation at double 45 degree inclination

What it fixes into

Timber based panels
Solid timber
Glulam
CLT and LVL
High density woods

The values for CLT and for high density woods such as Microllam LVL are tested, certified and calculated for those materials, not carried across from solid timber. The screw can also be used parallel to the grain.

The coating is electrogalvanised zinc, and that is what sets the working environment. VGZ is for service class 1 and 2, atmospheric corrosivity C1 to C2 and wood corrosivity T1 to T2. In plain terms, dry and covered work. It is not approved for external use, for unheated and damp conditions, or for coastal exposure. Service class 3 needs stainless steel or a zinc-aluminium flake coating, and this screw has neither.

Cyclic SEISMIC-REV testing has been carried out according to EN 12512 (VGZ technical data sheet, p.1). EN 12512 is a test method rather than a performance class. The European Technical Assessment covers connections under static and quasi-static loading, and seismic design of the connection stays with the project's structural engineer.

The tip, and which screws have it

Most of the range has the 3 THORNS tip, which reduces the minimum installation distances. More screws fit in less space, and larger screws fit in smaller elements, which the datasheet gives as a reduction in the cost and time of project implementation. It is on every 7 mm screw, on 9 mm screws up to 520 mm long, and on 11 mm screws up to 600 mm long. The two longest 9 mm screws and the eight longest 11 mm screws have a different self-drilling tip instead, so the reduced distances are not theirs. Check the length before you rely on the spacing.

Sizes

Three diameters. 7 mm runs from 80 to 400 mm, 9 mm from 160 to 600 mm, and 11 mm from 150 to 1000 mm. Drive is TX30, TX40 and TX50 respectively, and the bit is included.

Box quantity is not the same across the range. Every 7 mm screw, and every 9 mm screw up to 400 mm, comes 50 to a box. From 9 mm at 440 mm upwards, and across the whole 11 mm range, the box holds 25. The pack quantity is shown on every row of the table below, so read it from the row rather than assuming one figure for the range.

Before you fix

Above a characteristic timber density of 550 kg per cubic metre the screw must be driven into a pre-drilled hole. This one is not on the datasheet. It comes from the European Technical Assessment, and VGZ is not on its list of exceptions
Pre-drilling hole diameters are given for two cases and they are not the same. One is for softwood, the other for hardwood and beech LVL
The screws are approved for connections under static or quasi-static loading
Pull the elements together before the screws go in. The datasheet's method is to close the initial gap with a partially threaded screw first, then insert the VGZ, then take the temporary screw back out
Position the screws to the minimum distances. They are given separately for axial stresses, for shear loads, for CLT and for LVL, and separately again for installation with and without a pre-drilled hole. Do not read one case off another case's table
A row of screws does not give you the sum of the individual capacities. The datasheet gives an effective number to apply, both for screws in a row parallel to the grain and for pairs of crossed screws
The 45 degree applications rely on getting the angle right. The datasheet's method is to hold the angle for the first third of the drive, then finish without the guide
Dimensioning and verification of the timber elements is carried out separately, and instability of the connectors is verified separately
The assumed working life is 50 years. The European Technical Assessment states plainly that this is an assumption made for the assessment, not a guarantee

Design and specification support

The characteristic values, the minimum distances and the effective number tables are all in the Specifications tab and the linked datasheet. This is product-selection guidance. Final loads, quantities, spacing and sign-off must be confirmed by the customer's qualified structural engineer against the product ETA. See also our guide to Eurocode 5 timber design, our structural engineering support, and the full structural timber screw range.

Price shown is per box. The box holds 50 or 25 depending on the code, so check the pack quantity on the row. The table below gives codes, diameters, lengths and pack quantity.

Material

Carbon steel

Coating, and where it may be used

Electrogalvanised zinc, minimum 5 µm (ETA-11/0030, p.13). The coating is what sets the limit: service class 1 and 2 only, atmospheric corrosivity C1 to C2, wood corrosivity T1 to T2. Dry and covered work. Not external, not unheated and damp, not coastal. Service class 3 requires stainless steel or a Zn-Al flake coating, which this screw does not have

Head type

Cylindrical head

Thread and tip

Fully threaded. 3 THORNS tip on all Ø7 codes, on Ø9 up to and including L = 520 mm, and on Ø11 up to and including L = 600 mm. VGZ9560, VGZ9600 and the eight Ø11 codes from 650 to 1000 mm carry a different self-drilling tip, and the reduced installation distances stated for the 3 THORNS tip do not apply to those ten codes

Nominal diameter d1

7 mm · 9 mm · 11 mm

Head diameter dK

Ø9.50 mm (Ø7) · Ø11.50 mm (Ø9) · Ø13.50 mm (Ø11)

Thread diameter d2

4.60 mm (Ø7) · 5.90 mm (Ø9) · 6.60 mm (Ø11)

Threaded length b

L − 10 mm for every Ø7 code, every Ø9 code, and every Ø11 code up to and including L = 600 mm. L − 20 mm for VGZ11650 to VGZ111000, the eight longest Ø11 codes. L − 10 mm is not true across the whole range

Pre-drilling hole diameter, softwood

4.0 mm (Ø7) · 5.0 mm (Ø9) · 6.0 mm (Ø11). Valid for softwood only

Pre-drilling hole diameter, hardwood and beech LVL

5.0 mm (Ø7) · 6.0 mm (Ø9) · 7.0 mm (Ø11). Valid for hardwood and beech LVL only

When pre-drilling is mandatory

The screw must be driven into a pre-drilled hole where the characteristic member density exceeds ρk 550 kg/m³ (ETA-11/0030, p.8). VGZ is not on the ETA's list of exceptions. The datasheet gives the drill diameters but never states this threshold

Drive

TX30 (Ø7) · TX40 (Ø9) · TX50 (Ø11), bit included

Lengths, Ø7

80 to 400 mm in 20 mm steps, 17 lengths

Lengths, Ø9

160 to 400 mm in 20 mm steps, then 440, 480, 520, 560 and 600 mm, 18 lengths

Lengths, Ø11

150, 200, 250 and 275 mm, then 300 to 600 mm in 25 mm steps, then 650 to 1000 mm in 50 mm steps, 25 lengths

Static and quasi-static loading only (ETA-11/0030, p.4)

Characteristic tensile strength ftens,k

15.4 kN (Ø7) · 25.4 kN (Ø9) · 38.0 kN (Ø11)

Characteristic yield strength fy,k

1000 N/mm², all three diameters

Yield moment My,k

14.2 Nm (Ø7) · 27.2 Nm (Ø9) · 45.9 Nm (Ø11)

Withdrawal parameter fax,k, case 1

11.7 N/mm², solid timber, glued laminated timber, cross laminated timber and SWP members with maximum characteristic density ρk ≤ 440 kg/m³; associated density ρa = 350 kg/m³

Withdrawal parameter fax,k, case 2

15.0 N/mm², non-pre-drilled LVL with 410 ≤ ρk ≤ 550 kg/m³; associated density ρa = 500 kg/m³

Withdrawal parameter fax,k, case 3

29.0 N/mm², pre-drilled LVL or FST (ETA-14/0354) with 590 ≤ ρk ≤ 750 kg/m³; associated density ρa = 730 kg/m³

Other materials

For applications with different materials, see ETA-11/0030

Minimum distance a1, axial stresses

5·d1 → 35 mm (Ø7) · 45 mm (Ø9) · 55 mm (Ø11). To ETA-11/0030, independent of the insertion angle of the connector and of the angle of the force to the grain

Minimum distance a2, axial stresses

5·d1 → 35 mm (Ø7) · 45 mm (Ø9) · 55 mm (Ø11). Same conditions as a1

Minimum distance a2,LIM, axial stresses

2.5·d1 → 18 mm (Ø7) · 23 mm (Ø9) · 28 mm (Ø11), only where a1 · a2 ≥ 25·d1² is maintained for each connector

Minimum distance a1,CG, axial stresses

10·d1 → 70 mm (Ø7) · 90 mm (Ø9) · 110 mm (Ø11)

Minimum distance a2,CG, axial stresses

4·d1 → 28 mm (Ø7) · 36 mm (Ø9) · 44 mm (Ø11)

Minimum distance aCROSS, axial stresses

1.5·d1 → 11 mm (Ø7) · 14 mm (Ø9) · 17 mm (Ø11)

Reduced a1,CG and a2,CG at 45°

a1,CG = 8·d1 and a2,CG = 3·d1. Only for VGZ d = 7 mm, main-beam to secondary-beam, inclined or crossed at 45° to the secondary beam head, minimum secondary beam height 18·d, and only to the unloaded end and the unloaded edge

Minimum distances, shear loads

Not reproduced here. Four separate cases, with and without a pre-drilled hole and at load-to-grain angles of 0° and 90°, and the non-pre-drilled block carries a ρk ≤ 420 kg/m³ ceiling. See the datasheet

Minimum distances, CLT and LVL

Not reproduced here. Given separately for the lateral face and the narrow face of CLT, and for the wide face and edge face of LVL, each with its own minimum thickness and penetration conditions. See the datasheet

Effective number

The capacity of a group is lower than the sum of the individual capacities. An effective number is given for screws in a row parallel to the grain, and for pairs of crossed screws. See the datasheet

Characteristic value tables

Withdrawal, tension, sliding and shear values for timber, CLT and LVL are in the datasheet. They are calculated at ρk = 385 kg/m³ for timber, 350 kg/m³ for CLT and 480 kg/m³ for softwood LVL, with kdens conversion factors printed for other densities. No single value from them is usable without its table and its density basis

Reaction to fire

The screws are made from steel classified as Euroclass A1 for reaction to fire, to EN 13501-1 (ETA-11/0030, p.7). This is a material combustibility classification. It is not a fire resistance rating and says nothing about the load a connection carries in a fire

Instability

Connector instability must be verified separately. In compression the design strength is the lower of the withdrawal-side value and the instability value

Assumed working life

50 years. ETA-11/0030 p.4 states that this is an assumption made for the assessment and not a guarantee

Design code

EN 1995:2014, as printed on the datasheet

Certification

ETA-11/0030 · UKTA-083622/6195 · CE · UKCA

Pack

50 pieces per box for every Ø7 code and for Ø9 up to and including L = 400 mm. 25 pieces per box for Ø9 from L = 440 mm to 600 mm and for every Ø11 code. TX bit included. Pack size is not one number across this range: read it from the row in the code table

Brand

Rothoblaas

Structural reinforcementConcealed jointsTimber couplingsReinforcement orthogonal to the grainMain beam to secondary beam jointsSide-by-side joining of CLT floorsBeam coupling in renovation and new buildLight frame structuresCLT and LVLTimber-to-timber

Technical datasheet

PDF · Opens in new tab · Download from viewer

View datasheet ↗

Working out a whole connection? Get exact box quantities with our Fastener Calculator. Open calculator →

All sizes in the VGZ · Fully threaded cylindrical head screw range

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Code	Diameter	Length	Pack	Price ex VAT	Stock
VGZ780	7 mm	80 mm	50 pcs	£18.00	To order
VGZ7100	7 mm	100 mm	50 pcs	£20.50	To order
VGZ7120	7 mm	120 mm	50 pcs	£25.50	To order
VGZ7140	7 mm	140 mm	50 pcs	£31.50	To order
VGZ7160	7 mm	160 mm	50 pcs	£38.00	To order
VGZ7180	7 mm	180 mm	50 pcs	£45.00	To order
VGZ7200	7 mm	200 mm	50 pcs	£52.50	To order
VGZ7220	7 mm	220 mm	50 pcs	£61.00	To order
VGZ7240	7 mm	240 mm	50 pcs	£70.50	To order
VGZ7260	7 mm	260 mm	50 pcs	£81.00	To order
VGZ7280	7 mm	280 mm	50 pcs	£91.00	To order
VGZ7300	7 mm	300 mm	50 pcs	£101.00	To order
VGZ7320	7 mm	320 mm	50 pcs	£105.00	To order
VGZ7340	7 mm	340 mm	50 pcs	£117.00	To order
VGZ7360	7 mm	360 mm	50 pcs	£110.00	To order
VGZ7380	7 mm	380 mm	50 pcs	£141.50	To order
VGZ7400	7 mm	400 mm	50 pcs	£131.00	To order
VGZ9160	9 mm	160 mm	50 pcs	£42.50	To order
VGZ9180	9 mm	180 mm	50 pcs	£52.00	To order
VGZ9200	9 mm	200 mm	50 pcs	£61.50	To order
VGZ9220	9 mm	220 mm	50 pcs	£72.50	To order
VGZ9240	9 mm	240 mm	50 pcs	£83.00	To order
VGZ9260	9 mm	260 mm	50 pcs	£94.00	To order
VGZ9280	9 mm	280 mm	50 pcs	£105.00	To order
VGZ9300	9 mm	300 mm	50 pcs	£114.00	To order
VGZ9320	9 mm	320 mm	50 pcs	£122.50	To order
VGZ9340	9 mm	340 mm	50 pcs	£132.50	To order
VGZ9360	9 mm	360 mm	50 pcs	£142.50	To order
VGZ9380	9 mm	380 mm	50 pcs	£152.50	To order
VGZ9400	9 mm	400 mm	50 pcs	£163.00	To order
VGZ9440	9 mm	440 mm	25 pcs	£110.00	To order
VGZ9480	9 mm	480 mm	25 pcs	£138.00	To order
VGZ9520	9 mm	520 mm	25 pcs	£158.75	To order
VGZ9560	9 mm	560 mm	25 pcs	£176.25	To order
VGZ9600	9 mm	600 mm	25 pcs	£207.00	To order
VGZ11150	11 mm	150 mm	25 pcs	£28.25	To order
VGZ11200	11 mm	200 mm	25 pcs	£41.50	To order
VGZ11250	11 mm	250 mm	25 pcs	£67.25	To order
VGZ11275	11 mm	275 mm	25 pcs	£63.25	To order
VGZ11300	11 mm	300 mm	25 pcs	£90.50	To order
VGZ11325	11 mm	325 mm	25 pcs	£89.25	To order
VGZ11350	11 mm	350 mm	25 pcs	£104.25	To order
VGZ11375	11 mm	375 mm	25 pcs	£107.00	To order
VGZ11400	11 mm	400 mm	25 pcs	£127.50	To order
VGZ11425	11 mm	425 mm	25 pcs	£116.75	To order
VGZ11450	11 mm	450 mm	25 pcs	£151.00	To order
VGZ11475	11 mm	475 mm	25 pcs	£151.75	To order
VGZ11500	11 mm	500 mm	25 pcs	£205.25	To order
VGZ11525	11 mm	525 mm	25 pcs	£196.75	To order
VGZ11550	11 mm	550 mm	25 pcs	£241.75	To order
VGZ11575	11 mm	575 mm	25 pcs	£255.00	To order
VGZ11600	11 mm	600 mm	25 pcs	£296.00	To order
VGZ11650	11 mm	650 mm	25 pcs	£544.00	To order
VGZ11700	11 mm	700 mm	25 pcs	£564.00	To order
VGZ11750	11 mm	750 mm	25 pcs	£584.00	To order
VGZ11800	11 mm	800 mm	25 pcs	£629.25	To order
VGZ11850	11 mm	850 mm	25 pcs	£713.25	To order
VGZ11900	11 mm	900 mm	25 pcs	£770.75	To order
VGZ11950	11 mm	950 mm	25 pcs	£814.75	To order
VGZ111000	11 mm	1000 mm	25 pcs	£873.25	To order
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