To choose oak mantel beam sizes, measure the chimney breast or fireplace opening first, then pick three numbers: the length, the front height and the depth. Length decides how the beam sits against the wall, front height decides how heavy it looks, and depth decides how far it reaches into the room. Start with length, because it is the one you can't fix once the beam is cut.

Our solid oak mantel beams are made to order in European oak, in sizes from 3"x4" (7.6x10.2cm) up to 10"x6" (25.4x15.2cm). Here is how to narrow that down.

How long should an oak mantel beam be?

Lengths run from 3ft (91.4cm) to 6.5ft (198.1cm) in half-foot steps: 3ft, 3.5ft, 4ft (121.9cm), 4.5ft, 5ft (152.4cm), 5.5ft, 6ft (182.9cm) and 6.5ft (198.1cm).

Measure the width of the chimney breast, or of the opening if the beam sits tight to it. A beam that is just wider than the opening looks fitted. A beam that is much wider than the chimney breast can look like a shelf that has wandered off. If you want it to run the full width of the breast, measure the wall at the height where the beam will go, not at the skirting.

If your wall needs a length that isn't on the list, contact us with your measurements before ordering.

How deep and how tall should the beam be?

Beam sizes are given as front side x top side. So an 8"x6" (20.3x15.2cm) beam shows an 8" face to the room and is 6" deep on top. Examples from the range:

  • 4"x4" (10.2x10.2cm): a slim square profile. In our eye it suits a smaller breast.
  • 5"x5" (12.7x12.7cm): a middle square size, and a good place to start if you are unsure.
  • 6"x6" (15.2x15.2cm): a chunkier square beam that we find holds its own in a bigger room.
  • 8"x6" (20.3x15.2cm): a tall front face, which we would try on a wide breast or a high ceiling.

These descriptions are our judgement from making beams by hand, not a published rule. Trust your eye. Cut a cardboard template to the front face size, tape it to the wall and stand back.

Depth also has a practical side. A deeper beam sticks out further, which matters in a narrow room or beside a doorway. It also affects what you can stand on top.

Does the surface style change the size?

Slightly, to the eye. We offer three styles:

  • Sanded: smooth, with gently rounded edges.
  • Lightly Worked: more pronounced shaping along the edges, gently distressed.
  • Heavily Worked: deeper scalloping on the edges and visible faces, with a stronger rustic character.

Heavily worked edges read as more rugged, so you may want to go one size smaller so the beam doesn't dominate the wall. That is our view, not a rule. Oil colours are White, Light Grey, Grey, Dark, Old Oak and Clear, applied in our workshop, or we can supply the oil separately if you ask before ordering. Our oil colour comparison shows how they differ.

How does a beam sit next to a stove?

This is the part to check before you buy. Beam height above a log burner is set by the appliance, not by looks. Ask your stove or fireplace installer to confirm the manufacturer's required clearances to combustible materials. If you choose the Solid Oak Mantel Beam with Corbels, allow for the beam and the corbels together.

Use your appliance manual and your installer, not a figure from a product page, ours included.

What to measure before ordering

  1. Width of the chimney breast or opening, at the height the beam will sit.
  2. The height you can fix the beam at, once the installer has confirmed clearances.
  3. How far into the room you can go, depth-wise, before it gets in the way.
  4. Wall type. Our beams come with pre-drilled mounting holes and concealed fixings suitable for solid walls. For other wall types, check fixing suitability first.
  5. Ceiling height and any picture, mirror or TV you plan to hang above.

Which beam for which job

If you also plan shelves in an alcove, our guide to oak floating shelf thickness, depth and length covers the same sums.

Common questions

Are the sizes exact?

Each beam is hand-planed and sanded, so dimensions can vary by up to approximately ⅓ inch from the size you choose. Natural knots, cracks, splits and shakes are normal in oak and may change as the beam settles.

How long does a beam take to arrive?

Beams are made to order. Standard production is five working days before dispatch, delivery in the UK is free, and courier transit time is extra. Contact us before ordering if you need a date.

Can I order a length that isn't listed?

Contact us with your measurements before ordering.

Ready to pick a size? Browse the full range of solid oak mantel beams.