Smooth dowels carry load across a slab or pavement joint while letting the concrete on each side shrink, expand and move independently. To do that, one half of each dowel has to slide: it is debonded with a coating or bond breaker, or set in a sleeve. At expansion joints an end cap leaves room for the bar to move further in. And to keep a row of dowels straight and level while concrete is placed over them, they are held in dowel baskets, welded wire frames staked to the base.
Every one of those pieces exists for the same reason: a dowel that is bonded, tilted or skewed locks the joint it was meant to free. This guide covers what each part does, how Ontario's pavement specification treats them, and what to put on the order. For the basic difference between smooth dowels and rebar dowels, start with dowel bars vs rebar.
The parts of a doweled joint
| Part | What it is | Job |
|---|---|---|
| Smooth dowel bar | Plain round steel bar, usually coated | Transfers load across the joint |
| Bond breaker | Shop-applied coating, grease or form oil on the bar | Lets the bar slide in the concrete |
| Dowel sleeve | Plastic tube or pocket on one half of the bar | Debonds that half; often fixed to formwork |
| Expansion cap | Closed-end tube over one end of the dowel | Leaves a void so the bar can slide further at expansion joints |
| Dowel basket (load transfer device) | Welded wire frame holding a row of dowels | Keeps dowels at mid-depth, parallel and at spacing during the pour |
| Plate dowel | Flat steel plate in a pocket or sleeve | Used in some industrial floors where joints must move in more than one direction |
| Tie bar | Deformed bar across a joint | Holds a joint closed; the opposite of a dowel |
Tie bars appear on the same pavement drawings and are easy to confuse with dowels. Dowels let a joint open; tie bars keep it shut. The diameter, length and spacing of dowels and tie bars come from the pavement or slab design.
Sleeves, caps and bond breakers: making a dowel slide
A smooth bar on its own still grips concrete through friction and adhesion. Something has to stop that on at least one side of the joint:
- Shop-applied bond breaker. Ontario's draft pavement specification (OPSS.PROV 350, April 2023 draft) requires dowel bars and load transfer devices to be shop coated with a bond breaker, except for dowels installed into existing concrete. It names RC-250, Tectyl 506 or an alternative acceptable to the owner.
- Sleeves. On slabs built in panels, a common detail is a plastic dowel sleeve nailed to the form face at a construction joint. After the forms are stripped, the dowel is pushed into the sleeve and the next panel is placed around the exposed half. The sleeved half can slide; the other half is bonded.
- Expansion caps. At an expansion joint the slab is designed to move toward the joint as well as away from it, so the free end of the dowel needs room to travel. A cap with an empty space at its end, sized for the expected movement, provides that.
- Coatings. Epoxy coating protects against corrosion, and on pavement work the bars are also treated with bond breaker. Our post on epoxy-coated vs galvanized dowel bars covers the corrosion side.
One rule applies to all of them: don't try to turn deformed rebar into a dowel with grease. The ribs still key into the concrete and the joint stays locked.
How dowel baskets work
A dowel basket is a pair of wire frames (one on each side of the joint) connected by spacer wires, with the dowels welded or clipped at mid-height. The basket is set on the prepared base along the planned joint line, so the dowels sit at the right depth, at the right spacing, and parallel to the slab surface and the direction of movement.
Ontario's draft OPSS.PROV 350 sets out how load transfer devices are handled on provincial concrete pavement. Some of the requirements contractors on any slab can learn from:
- Dowels are not pushed in by hand. Dowel bars in plastic concrete go in with an automatic dowel bar inserter or by means of load transfer devices, not manual insertion.
- Baskets are staked. At least three stakes, uniformly spaced, on each side of the basket for each lane, so it can't move or roll during paving.
- Spacer wires are cut. After staking, the spacer wire is cut in two places and the middle section, at least 300 mm long, is removed. The usual reasoning is that intact spacer wires would act as a continuous tie across the joint.
- Baskets go in well ahead of paving, a minimum of 100 m ahead of the concrete placing operation under that specification.
- Alignment tolerance. Dowels must be parallel to the pavement's longitudinal axis and horizontal plane within ±15 mm along the length of the bar.
- Mid-depth. Dowels are placed at mid-depth, with tolerances that depend on the pavement thickness.
- The saw cut lands over the dowels. The centre of the dowels is marked so the transverse joint can be sawn within ±50 mm of it. A cut that misses the middle of the dowels leaves too little bar on one side.
Residential and commercial slabs on grade usually aren't built to a highway specification, but the logic is the same: staked baskets, straight bars, and a saw cut centred over the dowels.
Alignment: why a smooth dowel can still lock a joint
A tilted or skewed dowel behaves like a bent pin. As the joint opens, the bar tries to slide along its own axis, which is no longer the direction the slab is moving, so it binds. The result can be cracking or spalling near the joint, exactly what the dowel was meant to prevent.
That's why pavement work measures dowel alignment after paving. OPSS.PROV 350 references ASTM E3013/E3013M, a standard method for evaluating dowel alignment with magnetic pulse equipment. On building slabs, the practical checks are simpler: baskets sitting flat and square to the joint, stakes holding, and no bars kicked out of line during placing.
Dowels into existing concrete
When new concrete meets existing concrete, dowels are drilled and set in adhesive instead. OPSS.PROV 350's procedure is a good model:
- Holes drilled with a gang drill so they're parallel and correctly spaced
- Hole diameter no more than 5 mm larger than the bar
- Holes wire brushed, then cleaned with compressed air
- Epoxy adhesive injected from the back of the hole, with the bar inserted using a grout retention disk so the adhesive fully encases it
- Adhesives from MTO's approved list for horizontal applications; cementitious grout is not permitted for this use
For deformed dowels tying new work to old, see how to dowel rebar into existing concrete.
Storing and handling coated dowels
Coated dowels are easy to damage. The same draft specification limits unprotected on-site storage to 30 days and total on-site storage to 120 days, with protected bars covered in opaque polyethylene and kept clear of the ground on cribbing. Bars with coating damage under 1% of their surface are repaired; bars with more than 1% damage are rejected. In Ontario provincial work, dowel and tie bars are referred to OPSS 1440, epoxy coating to OPSS 1442 and load transfer devices to OPSS 1441.
On any project, read the contract's own dowel clause: acceptable dowel materials, coatings and assemblies vary between owners.
Ordering dowels and tie bars
Spell out what the joint needs:
- Joint type for each location: contraction, construction or expansion.
- Dowel diameter, length and spacing from the design.
- Coating and the standard it is specified to.
- Loose bars, sleeved bars or baskets, with basket height to suit the slab thickness.
- Tie bars separately, as deformed bar with size and length.
We fabricate rebar dowels, tie bars, L-bars and other bent shapes from 10M to 55M, cut and tagged to your drawings. If your job needs smooth or coated pavement dowels, tell us the specification when you ask for pricing; baskets, sleeves and caps come from accessory suppliers. Send us your drawings or see our rebar products. For what drives dowel pricing, see dowel bar prices in Canada.
Frequently asked questions
What is a dowel basket?
A dowel basket is a welded wire frame that holds a row of smooth dowel bars at the right height, spacing and alignment across a planned joint before the concrete is placed. Ontario's pavement specification calls it a load transfer device and requires it to be staked so it can't move during paving.
What is a dowel sleeve used for?
A sleeve is a plastic tube or pocket that one half of a smooth dowel slides in. It stops the concrete bonding to that half so the joint can open and close. Sleeves are often nailed to the formwork at a construction joint, with the dowel pushed in after the forms come off.
Do smooth dowels need to be greased?
At least one half of a smooth dowel must be debonded, by a shop-applied bond breaker, a coating, grease or a sleeve. Ontario's draft pavement specification requires dowels and load transfer devices to be shop coated with bond breaker, except dowels drilled into existing concrete.
Can you use rebar instead of smooth dowels at a slab joint?
Not at a joint that is meant to move. Deformed rebar bonds on both sides and locks the joint, so shrinkage shows up as a crack somewhere else. Deformed bars are right only where the drawings want the two pours tied together.
