Decking screws

Which screw for which timber?

The species decides before the diameter does. Softwood - pine, spruce - takes a 4.0 or 4.5 mm screw without special requirements. Hard and tannin-rich species call for stainless steel, pre-drilling and attention to the class of steel.

One point we state plainly: the manufacturer excludes the hardened stainless steel Hapatec is made of from timber high in tannins - „such as cumaru, oak, merbau, robinia etc.”. For those boards A4 is the only class the manufacturer calls suitable without qualification, and we do not currently stock A4. Write to us with the species and the location of the deck and we will source the right item. The whole picture, with the table of classes, is in the guide Larch decking - what to fix it with.

• Hapatec silver - hardened stainless steel, Ø 4.0-5.0 mm, lengths 30-100 mm, TX 15-TX 25 drive. For hardwood without a high tannin content.
• Hapatec black - same diameters, lengths 35-100 mm. The black head disappears on a dark board.
• Hobotec - Ø 3.2 mm, lengths 35-60 mm, TX 10 drive, ornamental head. For thin boards and cladding.

Why is galvanised steel ruled out on a deck?

Oak, larch, sweet chestnut and thermally modified timber contain tannins. In the presence of moisture they react with the zinc of the coating and form dark tannates, which soak into the timber around the head and run down the board in streaks. The stain reaches deep into the timber, so sanding rarely suffices; oxalic acid usually lightens it, but it returns if the iron source stays in the wood.

The mechanism, and how to tell such a stain from ordinary rust, is covered in the guide Oak, larch, thermowood - why zinc leaves black stains.

A2, A4 or hardened stainless?

A2 is enough in ordinary external conditions. A4 adds molybdenum and withstands chloride environments: the coastal belt, roads salted in winter, outdoor pools. The manufacturer does, however, exclude A4 from chlorine-bearing atmospheres, meaning indoor pool halls - there neither class is the right choice.

The third option is hardened stainless steel, which is what Hapatec is made of. It takes a higher driving torque and therefore copes with hard timber - but it is not the same thing as A4 and does not replace it where the environment is what decides. The guide A2 or A4 - which stainless steel to choose settles the difference.

Visible or concealed fixing?

Visible means a screw from above, through the board, head on top: simplest, cheapest and easiest to service. Concealed drives the fastener at an angle from the side of the board, so not a single head shows on the surface.

The second method uses the Drill Tool 50X - a jig that sets the angle, a 3.3-4.5 mm step drill and a 50X A2 4.2 x 60 mm screw in the set. Working with the jig needs the long 50X TX 15, 82 mm bit, because a standard bit will not reach into it.

What to order alongside?

• TX bits - the drive on decking screws sits between TX 15 and TX 25. The colour-coded 25 mm set covers TX 10 to TX 40; the long 50 mm version reaches TX 50 and gets into awkward places.
• Substructure - boards sit on joists, joists sit on pedestals. You will find the adjustment ranges in the adjustable pedestals category.
• Load-bearing fasteners - for the deck structure itself, see construction screws.

How do we count packs?

Screws come in the manufacturer’s packs, and the pack size depends on the diameter: Hapatec 4.0 mm in 500 pieces, 4.5 and 5.0 mm in 200, Hobotec in 500. The selector gives the size together with the pack, for example 4.0 x 50 mm · 500 pcs, and the quantity in the basket means the number of packs, not of individual pieces.

There are two units of sale and you cannot read them off the name: pedestals go per piece, screws by the pack. For accessories, read the pack size from the product page - it is in the selector and in the article table, together with the Eurotec article number and EAN. The shop search accepts both.