Building a Styrofoam Block Pool – Complete Build Report
A Styrofoam block pool can be built yourself if you get the sequence right. This build report guides you from the excavation pit through the base slab and the filled formwork blocks to the built-in parts, pipework and backfilling – with a rough timeline and materials overview.
Excavation and Blinding Layer
Construction begins with the excavation. Plan the pit to be around 30 to 50 cm larger all round than the later outer pool dimensions, so that enough working space remains for placing the blocks, fitting the built-in parts and backfilling. The excavation depth is the pool depth plus the base slab and the blinding layer.
Assess the subsoil critically: if groundwater is present or the soil is cohesive, a ring drainage and a load-bearing gravel bed are required. The blinding layer of lean concrete or compacted chippings goes onto the compacted subgrade. It creates a level, clean working surface for the subsequent base slab.
If in doubt, have the load-bearing capacity of the subsoil and the need for drainage assessed by a specialist contractor or a soil survey.
Base Slab with Reinforcement
The base slab takes the weight of the water and the pool walls. A reinforced concrete slab is standard; its thickness and reinforcement depend on the pool size and the subsoil. The exact design of the reinforcement – mesh layers, bar diameter, lap length – belongs in the hands of a structural engineer or your executing specialist contractor; do not make up any values here.
Lay the reinforcement mesh on spacers so that it is completely enclosed by the concrete. It is advisable to use starter reinforcement that projects out of the slab and is later cast into the first course of blocks – this creates a rigid, moment-resistant transition between the floor and the wall. Pour the slab in a single operation if possible and screed it level and true.
Placing the Block Courses and Filling with Concrete
After the slab has cured, the Styrofoam formwork blocks are placed course by course. The first course determines the dimensional accuracy of the entire pool: align it exactly at right angles and level. The blocks are dry-fitted into one another, not laid in mortar.
The vertical and horizontal reinforcement goes into the hollow cores according to the structural engineer’s specifications. The cores are then filled course by course with a highly flowable core concrete. Do not concrete the full height in one go, but in sections, so that the fresh concrete pressure does not shift the lightweight blocks. Check alignment and plumb continuously and brace the walls if necessary.
Fitting the Built-in Parts: Skimmer, Nozzles, Main Drain
Before or during filling, you fit the built-in parts: skimmer, inlet nozzles and – if planned – the main drain and the light niche. The recesses can be cut cleanly into the Styrofoam blocks with a knife or saw.
Pay attention to the correct heights: the skimmer determines the later water level, and the inlet nozzles sit a few centimetres below it. Fix the parts precisely in position before the concrete encloses them, and seal the openings against ingressing concrete. The main drain and light niche must be connected – or the conduit laid – before concreting, as they are no longer accessible afterwards.
Safety-critical and mandatory to prepare already in this shell-construction phase is the protective equipotential bonding. In accordance with DIN VDE 0100-702, the continuous steel reinforcement and all conductive parts in the pool area – including the underwater light and its niche – must be integrated into the equipotential bonding. To do this, attach the connection tabs to the reinforcement and lay the conduit while the components are still accessible; making this connection retrospectively is barely possible. The entire electrical installation at the pool – including the execution and certification of the equipotential bonding – belongs in the hands of a qualified electrician.
Pipework and Backfilling
From the built-in parts you run the lines to the equipment. For small to medium-sized private pools, pressure pipe d50 (DN40) is usually sufficient; for larger pools or a high circulation rate, choose d63 (DN50). Skimmer, suction and nozzle lines are made in PVC-U and solvent-welded with cleaner and PVC cement.
Fit unions at the skimmer and at the equipment so that the connections remain releasable without damage. Shut-off ball valves allow individual lines to be isolated separately. Lay the pipes with a slight fall and plan drainage options for the winter now.
The backfilling is carried out course by course with compactable material, in parallel with the concreting or after curing. Backfill evenly all round so that no one-sided earth pressure acts on the wall that has not yet cured. Compact in layers, but gently, so as not to damage the lines and walls.
Timeline, Materials List and Costs
A self-build can be roughly divided into the following phases. The time figures are guide values for a medium-sized pool (about 8 x 4 m) built yourself and depend heavily on the weather, helpers and curing times.
| Phase | Work | Rough duration |
|---|---|---|
| Excavation & blinding layer | Pit, gravel bed, lean concrete | 1–2 days |
| Base slab | Reinforce, concrete, cure | 1 day + curing |
| Block courses & filling | Place, reinforce, concrete | 2–4 days |
| Built-in parts & pipework | Fit, cement, connect | 1–2 days |
| Backfilling | Compact course by course | 1 day |
| Fleece, liner, filling | Lay out, hang in, flood | 1–2 days |
The costs are dominated by earthworks, concrete and reinforcement, the formwork blocks, fleece and liner, and the equipment. Include a reserve for offcuts and small materials. You will only get a reliable cost estimate once you have concrete quantities from your own planning.
Building a Styrofoam Block Pool Step by Step
- Excavate the pit Excavate the pit with all-round working space, compact the subgrade and screed it level with a gravel bed and blinding layer.
- Concrete the base slab Lay the reinforcement mesh on spacers, provide starter reinforcement, and concrete the slab in a single operation and screed it level. A structural engineer handles the design.
- Align the first course of blocks Align the first course of formwork blocks exactly at right angles and level on the cured slab – it determines the dimensional accuracy of the pool.
- Build up and reinforce the block courses Dry-fit further courses, insert vertical and horizontal reinforcement as specified, and check alignment and plumb continuously.
- Fill with core concrete Fill the cores course by course with flowable concrete, not the full height at once, so that the lightweight blocks are not shifted.
- Fit the built-in parts Cut out recesses for the skimmer, nozzles and main drain, fix the parts precisely at the correct height and seal them against ingressing concrete. Have the protective equipotential bonding of the reinforcement and light prepared now by a qualified electrician in accordance with DIN VDE 0100-702.
- Pipe up and connect Solvent-weld lines in PVC-U d50 (DN40) with cleaner and cement, fit unions and ball valves, and run them to the equipment with a fall.
- Backfill, liner, filling Backfill and compact course by course all round, hang in the fleece and pool liner, and flood the pool in parallel with the remaining backfilling.
Bill of materials
Example – please verify with a specialist. Parts and quantities depend on the installation; sizes shown are examples.
| Component | Size | Art. No. | KLN No. | Qty |
|---|---|---|---|---|
| PVC-U pressure pipe with socket | d50 | 76910 | 51515804 | approx. 20–30 m |
| 90° Bend, solvent socket (PVC-U) | d50 | 70979 | 51513442 | 6–10 pcs |
| 90° Elbow, solvent socket (PVC-U) | d50 | 70506 | 51513082 | 4–6 pcs |
| 90° Tee, solvent socket, equal (PVC-U) | d50 | 70022 | 51512912 | 2–3 pcs |
| 2-way ball valve M1, solvent socket (PVC-U) | d50 | 128814A | 51511559 | 2–4 pcs |
| Union Ocean, solvent socket / solvent socket | d50 | 170397 | 51512461 | 3–5 pcs |
| Socket, solvent socket (PVC-U) | d50 | 70739 | 51513256 | as needed |
| Griffon UNI-100 PVC-U adhesive | – | 20023 | 51512566 | 1–2 cans |
| Griffon cleaner / degreaser | – | 1 can | ||
| Styrofoam formwork blocks (EPS) | – | – | – | Wall building blocks of the pool; quantity based on perimeter and height |
| Reinforcing steel / reinforcement mesh | – | – | – | Sizing by a structural engineer or specialist contractor |
| Ready-mixed concrete for base slab and core fill | – | – | – | Strength class per structural specification |
| Skimmer and inlet nozzles (ABS built-in parts) | – | – | – | Determine the water level and flow routing |
| Pool fleece and lining membrane | – | – | – | Protective fleece plus inner liner as the water-bearing layer |
| Sand filter system with circulation pump | – | – | – | Sized according to pool volume and turnover factor |
FAQ
Do I need a building permit for a Styrofoam block pool?
That depends on the pool volume, the location and the respective state building code. Clarify whether a permit is required with your responsible building authority before construction begins.
Does the reinforcement have to be calculated by a structural engineer?
For the base slab and wall reinforcement, the structural design and the subsoil are decisive. Have the structural specifications determined by a structural engineer or your specialist contractor and do not invent your own values.
Which concrete do you use for the core filling of the formwork blocks?
A highly flowable concrete that fills the cores without voids is standard. The exact strength class depends on the structural specification.
Which pipe dimension do I need for the pipework?
For small to medium-sized private pools, d50 (DN40) is usually sufficient; for larger pools or a high circulation rate, choose d63 (DN50).
How long does the build take when done yourself?
For a medium-sized pool, several weeks are realistic including curing times. The actual working time is spread over roughly one to two weeks, depending on the weather and helpers.
This guide provides general technical orientation and does not replace professional planning. Safety-, electrical- and permit-relevant work must be carried out by qualified specialists.
