Johns Manville GoBoard 1/2 in Tile Backer (3x5) Review (2026)
By Nate Sawyer, Editor · 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 |
Frequently Asked Questions
- Can GoBoard be used on floors, or is it only for shower walls?
- Both. It is rated for studs, walls and floors over a subfloor, so the same 1/2 in panel works for a wet floor as for a shower surround. Each 3x5 board covers 15 sq ft.
- Do you still need a separate waterproofing membrane over GoBoard?
- No, and that is the main reason to pay for it. The polyiso core is waterproof to ASTM D4068 with a perm rating under 1.0, so only the joints and screw heads need sealing to make the assembly watertight. That said, sealing them with the maker's sealant is not optional - skipping it in a shower is the one mistake that undoes the whole product.
- How do you cut GoBoard?
- With a standard utility knife, and with almost no dust. That is a real difference from cement board, which you score and snap or cut with a wet saw and which coats the job site in silica dust.
- Is GoBoard worth the extra cost over cement board?
- It costs noticeably more per board than fiber-cement or aggregated cement backer, so the value depends on what you are buying out of. What you get is up to 80% less weight - a genuine difference when hanging a panel overhead alone - no dust, and no separate membrane step. The offsetting care item is fastening: the foam is softer, so screws need washers and must not be overdriven.