Anchor Bolts for Poles and Masts: What They Are and How to Choose Them

What an anchor bolt in a pole foundation is

An anchor bolt holds the pole on its foundation. The lower part of the stud sits in the concrete and the upper part stands above the surface. The flange of the lowest pole section is set over these studs and fixed with nuts.

For masts, towers and power line poles it is mostly the wind moment, not the weight of the structure, that sets the size of the foundation. The bolts belong to the same joint, so they are chosen for the load at the base of the pole (more in the article on foundations for masts, towers and line poles).

Such bolts are used under lighting columns, floodlight masts, BKM catenary poles, flagpoles and telecom towers. BKMG poles, which are set straight into the ground without a flange, need no bolts.

Bolts, anchor cage and template: how they relate

Bolts are not set into the concrete one at a time. They are assembled into an anchor cage, where templates fix the bolts in the design position until the concrete has gained strength. A hole in the flange is only slightly larger than the bolt, so keeping the bolts in the right position relative to each other matters more than placing the group exactly on the axis.

The cage is cast into the foundation in advance. Once the foundation is ready, the pole is set on the studs with no fitting on site.

In the Foundation Anchor Cages and Anchor Bolts section the cages are split by purpose: FPO for lighting columns, FPM and FPMV for floodlight masts and lightning masts, FKM for BKM poles. We do not repeat the size tables here; they are in the article on foundation anchor cages. We also supply cages separately from poles, for example when the foundation is prepared first.

What sets bolt diameter and number

Selection starts from the pole, not from the bolts. The diameter, the number of bolts and the spacing between them must match the holes in the pole flange.

Flange and bolts grow with pole height. On PMO park poles, at 6 m the bottom diameter grows from 168 to 206 mm, the flange from 250×250 to 300×300 mm and the anchors from M20 to M24. On floodlight masts and towers the bolts are larger (M30 to M42) and there are 12–20 of them in a joint.

Values from our pages on anchor cages, floodlight masts and telecom towers; for your pole the bolt diameter and number are confirmed by calculation.

What else affects the choice

The load at the base depends on the height, on what the pole carries (luminaires, antennas, a flag) and on the wind region. For regions see the article on wind regions of Ukraine. For a flagpole, the height, diameter and number of anchors are chosen for the pole height and the size of the flag.

Taking a larger cage “just in case” does not work: on a PMO-7 with four M24 bolts (B 220) an FPO-1500-3 cage with M27 bolts (B 300) will simply not fit.

If a pole is to go on a ready foundation designed for another pole, the bolt layout and diameter are checked, along with whether the loads stay within the design values. A drawing is needed for that.

Material, coating and thread protection

We make anchor cages from C245/C345 steel to DSTU 8539:2015 and supply them without a coating.

Before erection the thread is protected from concrete splashes. How the thread above the concrete is protected against corrosion is set by the design; for general approaches see the article on corrosion protection.

In a line design the bolts can also be a link in the earthing. For overhead lines up to 1 kV the PUE (2026 edition) requires a metal connection between the pole’s metalwork and the foundation reinforcement (cl. 2.4.33). Earthing of lighting poles is covered separately: earthing of metal poles.

How bolts get into the foundation and what is checked

The cage is placed in the formwork and cast with the foundation, before the pole is erected. For a flagpole this is usually done by the customer. Before concreting, the cable duct and the earthing outlet must be in place, and the cage is braced so that the pressure of the mix does not move it.

The vibrator is not rested on the cage. Each bolt is checked and the result is written into an as-built diagram. A bolt that has drifted is corrected before the pole arrives, not by forcing the flange on site.

The pole is set when the concrete has reached the strength required by the design. Then the order is:

• the pole is set on the bolts, matching the control mark on the flange to the mark on the cage;
• verticality is checked; if needed the flange rests on levelling nuts and the gap is filled with non-shrink grout;
• it is fixed with nuts, a lock nut keeps them from backing off, and the slings come off only after all nuts are fully tightened;
• on flagpoles the nuts are recommended to be tightened once more after a week.

Poles, towers and masts are erected by a licensed building partner company; flagpoles are usually erected by the customer, and if needed we arrange erection through a partner. For flagpoles see How to install a flagpole. The nut tightening torque is set by the design and the pole drawing.

What to send us for bolt selection

To select the bolts and the cage, these data are enough:

• the type and height of the pole, or its mark;
• a drawing or sketch of the flange: size, number and diameter of the holes, spacing between them;
• the load at the base if a calculation exists; if not, the equipment on the pole and the site location (wind region);
• the number of poles;
• whether the foundation is already built: then we check its layout against the pole.

Send this through the order form (see How to order poles and masts), and we will select the size, calculate the cost and the production time.