A pole crown is in air and still drinks water

IN AIR is the whole of a pole's exposure, and on its own it protects nothing: the crown is the single horizontal sawn face on an otherwise vertical part, so rain stops there rather than running off.

Confirm a size against the five-size span

The crown is a different exposure from the pole

Place the crown on the scale before you place the pole. From ground line to top a pole sits IN AIR, and that is the most forgiving of the four bands to design against: no backfill, no tide, no duct standing full of water. The crown occupies the same band and behaves nothing like the rest of it, because it is cut square across the grain and faces the sky.

End grain takes water the way a bundle of open tubes does, so a crown wets deeper and dries slower than any sawn face further down. Drying opens checks along the grain, the checks hold water instead of shedding it, and each winter's freeze-thaw widens them a little further. Decay then works downward from the one face on the whole structure that nobody puts a ladder up to look at until the pole is already on a replacement list.

Two moulded parts are offered for that face and only one of them goes into the timber. The heat-shrink cap arrives expanded and recovers above 125°C (257°F) under a soft blue propane or butane flame; as the wall pulls down over the top, the hot-melt lining melts and penetrates the cracks and cavities in the pole top, reinforcing it as it cools. The push-on cap in moulded PVC covers precisely the same crown and does none of that. Everything further down this page follows from that one difference.

Heat-shrink pole cap, five sizes

A closed-top heat-shrinkable cap, lined inside with hot-melt adhesive and supplied in an expanded form. It goes on with a gas torch, closed end first, and the finished signal is adhesive showing all round at the skirt. Once recovered and cooled, the manufacturer publishes the construction as giving 100% environmental sealing to IP68.

The lining reinforces a checked crown; the cap wall on its own only covers it
One torch application, worked round the circumference from the closed top downward
The same part serves a timber crown, a spun concrete top, a steel pole and a composite pole

Exposure band	IN AIR, at the crown
Top diameters covered	140-460 mm (5.5-18 in), in five sizes
Substrates	Wood, concrete, steel or composite poles
Lining	Hot-melt adhesive, entering checks and cavities on recovery
Sealing	100% environmental sealing to IP68
Recovery	Above 125°C (257°F), propane or butane torch
Applications per pole	One
Service life	More than 30 years
Maintenance after fitting	None

IP68ASTM D638ASTM D570ASTM D2671ESI 09-11ASTM D149ASTM D257ASTM D150

What changes at the top once the crown is closed

Only the first is about water. The second and third are usually what gets the line funded.

Rain no longer reaches the end grain, and it is the bond doing that rather than the shape. The lining sets round the full circumference of the crown, so there is no path in under the skirt.
Birds stop using the crown. A domed top with no flat landing area prevents perching and nesting, which on timber is the same thing as stopping excavation at the top.
The manufacturer publishes elimination of outages caused by flash-over and electrocution at the pole top. That is a claim about the top being covered, and it is worth reading as such before it is put in a business case.
Freeze-thaw stops widening the checks, because the checks stop taking water.
The crown stops being a recurring inspection item: more than 30 years of published service life from a single application, with nothing to revisit. How that behaves across a route rather than a pole is set out on utility pole top maintenance.

What is published against these caps, and what is not

Size: Five sizes span 140 to 460 mm (5.5 to 18 in) of top diameter. The manufacturer publishes the span and not a row per size, so a size is settled against a measured crown and nothing finer appears here. The span sits beside the cable, anode and gland codes on the size chart.
Sealing: 100% environmental sealing to IP68, claimed for the recovered cap with its adhesive lining. Read that as a bond round the crown, not as a cover shedding water by shape.
Weathering: Resistance to ultraviolet and ozone, published for both the heat-shrink and the moulded PVC cap.
Tensile strength and elongation: Held against ASTM D638 for the heat-shrink cap and against ASTM D638 for the PVC cap.
Water absorption: Held against ASTM D570, for the heat-shrink cap only.
Heat ageing and heat shock: Held against ASTM D2671 and ESI 09-11.
Electrical and physical methods: Dielectric strength against ASTM D149; volume resistivity against ASTM D257; dielectric constant against ASTM D150. The PVC cap is published against ASTM D149, ASTM D792 and ASTM D2240. None of these methods is decoded here, because what an end-cap datasheet proves does it once for the whole site.
Not published: No per-size dimension table for the pole range, no uplift or pull-off figure, and no cold-shrink pole cap of any description. Where the datasheet carries no number, none is printed. Ordering variants sit on the manufacturer's own page for this cap.

The fork is the torch, not the pole

Both parts fit the same five-size span on the same four substrates. What separates them is whether a flame is going up that pole at all.

Decision point	Heat-shrink cap	Push-on PVC cap
Fitting	Gas torch, above 125°C (257°F), flame kept moving round the circumference	Pushed on by hand; no tools, no skill
Hot-work permit	Required, and on a live route that is often the binding constraint	Not required
What reaches the checks	Adhesive flows into cracks and cavities and reinforces the top	Nothing. The crown is covered, not consolidated
Ingress	100% environmental sealing to IP68	No ingress rating published
Impact	Not listed for the pole cap	Resists cracking on sharp-edge impact
Weathering	UV and ozone resistant	UV and ozone resistant
Birds	Perching and nesting prevented	Perching and nesting prevented
Freeze-thaw	Prevented by keeping the checks dry	Published as protecting the top from freeze-thaw damage
Coming off again	Cut away. The bond is permanent	Not bonded, so nothing has to be cut
A crown that has already checked	The case it exists for	The case it is not for

Push-on PVC pole caps, where no torch is coming

Same crown, same band, closed a different way. The cap is moulded in a specially formulated PVC, pushed on by hand and finished in minutes, with no flame, no permit and no trained fitter. On a live distribution route, or anywhere a hot-work permit is refused, that is the only argument in the comparison that carries weight.

Round is the profile most poles take: a domed top on a parallel skirt. Square is moulded as a pyramid top on a square skirt, for a sawn or laminated post rather than a turned pole. Those two are what the manufacturer publishes; anything else is a moulding question to put to the manufacturer's page for the moulded cap, and this site quotes no tooling, stock or ordering position on it.

What is given up is the whole of the left-hand column. Nothing flows into the checks, a crown that has already opened is covered rather than consolidated, and no ingress rating is published for it. Closing a sound crown before it opens, that trade is usually the right one. Closing a crown that is already split, it is not.

Two moulded black PVC pole caps photographed side by side: at left a round cap with a domed conical top, at right a square cap with a pyramid top, both on a plain parallel skirt.

Questions that come up before a crown is capped

Do I measure the crown or the pole?

The crown, across the top, where the cap will actually sit. A pole tapers, so a diameter taken at chest height sends you one size too large and the recovered wall never pulls down onto the timber. Five sizes cover 140 to 460 mm (5.5 to 18 in), and a measured figure is what confirms one of them.

Will a cap work on a crown that has already checked?

That is the case the heat-shrink cap exists for: the adhesive penetrates the cracks and cavities as the cap recovers, and reinforces the top as it sets. A push-on cap over the same crown covers those checks and leaves them exactly as they are. Where a split runs down past the depth the skirt reaches, the crown is a replacement decision rather than a capping one.

Does capping the top protect the rest of the pole?

No — it closes one face, and the ground line is a different band on the same pole belonging to a pole protection sleeve, which is not described here.

Is this the same part as a dock pile cap?

The same moulded shape and the same five sizes, at a different depth. A timber pile is cut off in the SPLASH ZONE and takes wetting from below as well as from above, which changes what the cap has to survive rather than what it is; that is dock pile caps.

Our contractor cannot get a hot-work permit. What then?

Then the heat-shrink cap is out on that route however the crown looks, and the push-on cap above is what gets specified. The general form of that constraint, across every part on this site, is on end caps where no flame is allowed.

Is a pole cap the same thing as pile capping?

No, and the two terms collide badly in search results. Pile cap or pile capping separates the moulded cover from the civil-engineering structure that shares the name.

Where this decision goes next

Down the scale, out to the programme, or into the fitting detail.

Getting a crown size confirmed

Open End is a reference site: it does not make these caps, keep them on a shelf, or put a figure against them. Four facts turn a pole enquiry into a single reply: the measured crown diameter, the pole material, whether the crown has already checked, and whether a hot-work permit is obtainable on that route.

What to put in the enquiry Read the five-size span first