How to Thicken Surface in SOLIDWORKS

The Thicken command turns a surface body into a solid by adding thickness to one side, the other side, or both sides of the selected surface. It is useful when you build shape with surfaces first and then need a manufacturable solid part.

Prepare the surface

Before using Thicken, inspect the surface body. The surface should be clean, continuous, and free of tiny gaps or self-intersections. If the surface has open edges, that can be fine, but the offset thickness still needs enough room to solve.

It also helps to decide whether the surface represents the inside, outside, or middle of the final wall. That decision affects which direction you thicken and whether important outside dimensions remain unchanged.

Use the Thicken command

1. Select the surface body or surface faces you want to thicken.
2. Go to Insert > Boss/Base > Thicken.
3. Enter the thickness value.
4. Choose the direction: one side, opposite side, or both sides.
5. Check the preview and accept the feature.

Choose the right direction

The direction matters because thickening offsets the surface. For an outside shell, you may want the thickness to go inward so the outer shape stays unchanged. For a cover or cap, you may want the thickness to grow outward or split equally around the original surface.

Use the preview to check whether the part grows into nearby geometry or creates an unexpected offset.

If the part must mate to other components, check those fit surfaces after changing the direction. A small thickness direction mistake can shift the functional face of the part.

Fix failed thicken features

If Thicken fails, reduce the thickness and try again. Sharp corners, tight curvature, and small surface features can cause offset geometry to overlap. You can also repair or simplify the surface before thickening it.

When a surface is too complex to thicken in one step, split it into smaller areas, thicken simpler regions, or use surface tools to create a cleaner boundary.

For imported surfaces, run import diagnostics or repair tools before thickening. Imported edges may look acceptable visually while still causing offset failures.

Check the solid after thickening

After the feature rebuilds, confirm that the result is a solid body if that is what you need. Check mass properties, section views, and any downstream features that depend on the new body.