Johns Manville GoBoard 1/2 in Tile Backer (3x5) Review (2026)
By The DIYPicks Team · Updated July 2026
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- Showers
- Wet floors
- Lightweight
The lightweight waterproof upgrade to cement backer board: a polyiso foam panel that cuts with a utility knife, weighs a fraction of Durock, and needs only its seams and screws sealed to build a watertight shower or wet floor. You pay more per sheet and must fasten it carefully, but it removes the dust, weight and separate membrane of cement board.
Pros
- Fully waterproof core means only the joints and screw heads need sealing for a watertight shower or floor
- Cuts with a standard utility knife and almost no dust, unlike score-and-snap or wet-saw cement board
- Up to 80% lighter than cement board, so a single sheet is far easier to handle and hang overhead
Cons
- Costs noticeably more per board than fiber-cement or aggregated cement backer
- Foam board is softer, so fasteners must be set correctly with washers and not overdriven
- Joints and penetrations must be sealed with the maker's sealant, a step that is disastrous to skip in a shower
Specifications
| Type | Polyiso foam backer board |
|---|---|
| Base | Studs, walls, floors (over subfloor) |
| Thickness | 1/2 in |
| Coverage | 15 sq ft (3 x 5 ft) |
| Waterproof | Yes (ASTM D4068, perm <1.0) |
| Weight | Up to 80% lighter than cement board |