Description
The XPS foundation board 30mm is the thinnest board in the Renders World XPS foundation board range: blue, water-repellent, 1000 × 500 mm and sold singly. It is the one to reach for when a plinth or a foundation wall has only a few centimetres of depth to give.
When the XPS Foundation Board 30mm Is the Right Choice
Most foundation work takes a thicker board. The XPS foundation board 30mm earns its place where something fixes the depth — a path laid tight against the wall, a door threshold, or a facade above the DPC that is itself only 30 mm thick. Typical places:
- Thin plinths from ground level to the DPC, kept close to the wall line.
- Foundation walls below ground where the trench leaves little working room.
- Short runs and repairs on the foundation perimeter, bought board by board.
Why Buy the 30 mm Board
- The least depth in the range, so your plinth hardly stands out from the wall above it.
- About 0.75 m²K/W of thermal resistance: 0.030 ÷ 0.038 = 0.79, rounded down to 0.75.
- Same strength as the thicker boards: 100 kPa in compression and 150 kPa in bending, from the CE marking.
- 5 % water absorption under long-term immersion, the figure every board in the range carries.
Specification — XPS Foundation Board 30mm
| Property | Value |
|---|---|
| Board | XPS foundation board, blue, water-repellent |
| Thickness | 30 mm |
| Board size | 1000 × 500 mm (0.5 m²) |
| Sold as | 1 board |
| Thermal conductivity λD | 0.038 W/mK |
| Thermal resistance | 0.75 m²K/W (0.030 ÷ 0.038 = 0.79, rounded down) |
| Compressive strength | 100 kPa |
| Bending strength | 150 kPa |
| Water absorption, long-term immersion | 5 % |
| Reaction to fire (the board alone) | Class E |
Fitting the 30 mm Board With the Wall Above
Where the facade is 30 mm, the 30 mm graphite EPS facade board continues above the DPC in the same plane. Bond the foundation board with an adhesive from the adhesives and basecoats for insulation boards, take the starter track and anchors from the insulation fixing accessories, and close the visible plinth with a mosaic plinth render that copes with splash water. The plinth thermal bridge guide explains why the join at the DPC matters more than the board's depth.
30 mm Against the Deeper Boards
| Board | Thermal resistance (thickness ÷ 0.038) | Typical place |
|---|---|---|
| 30 mm (this board) | 0.75 m²K/W | Thin plinths where little depth is free |
| 50 mm | 1.30 m²K/W | Shallow plinths and foundation wraps |
| 80 mm | 2.10 m²K/W | Plinths under an 80 mm facade |
| 90 mm | 2.35 m²K/W | Plinths under a 90 mm facade |
| 100 mm | 2.60 m²K/W | Deepest wrap, 100 mm facades |
Every depth has λD 0.038 W/mK. If the detail can take 50 mm, the 50 mm foundation board gives about 1.30 m²K/W instead of 0.75. To see what each depth means for the whole wall, use the U-value and insulation thickness guide.
How Many 30 mm Boards
Each XPS foundation board 30mm covers 0.5 m², two to the square metre, and Renders World sells it one board at a time. Work out the area of the plinth or foundation strip, double it, round up, and keep a board or two spare for corners and cut ends.
FAQ — XPS Foundation Board 30mm
How big is one board?
1000 × 500 mm and 30 mm thick — 0.5 m² per board, so two boards cover a square metre. You can order exactly the number you need.
Is a 30 mm board as strong as the thicker ones?
Yes. Compressive strength is 100 kPa and bending strength 150 kPa at every depth in the range; only the thermal resistance changes with thickness.
Should I take 30 mm or 50 mm?
Take the thickest board the detail allows. 30 mm is for plinths and foundation strips where there is no room for more; with 20 mm to spare, 50 mm gives about three quarters more thermal resistance (1.30 against 0.75 m²K/W).
What does fire class E mean for a rendered plinth?
It is the class of the board on its own. A rendered plinth is assessed as a complete system, and the wall takes its class from that system.
What do I bond the 30 mm board with?
A board adhesive from the adhesives and basecoats range. Before you buy, check the adhesive's own sheet: it should name XPS boards and, for the part below ground, damp use.