Select Project Scale: Custom Indoor House Rooms or Concrete Slabs
Choose a residential room over wood subfloor, dial in exact custom dimensions, or load a full garage/shop concrete slab:
1. Room Geometry & Floor Assembly
Dial in custom room dimensions, cabinet deductions & subfloor type
Subtract cabinets, kitchen island, tub, vanity, or closets
2. Scaled Room / Slab Blueprint & Serpentine PEX Routing
6" perimeter setback • Routes serpentine PEX around unheated cabinet/island zones
3. Complete System Bill of Materials (BOM) & Hardware Spec List
Dynamically matched to your 16'×22' (300 net sq ft) configuration, including exact PEX footage, manifold/zone hardware, floor-safe mixing valve, and Omega Aluminum Heat Transfer Plates.
O2-Barrier PEX Tubing Specs (Indoor & Slab)
ASTM F876 / F877 & DIN 4726 hydraulic & loop limits
| Size | ID (in) | Max Loop | Gal/100' | Best Application |
|---|---|---|---|---|
| 3/8" PEX | 0.350" | 200 ft | 0.50 gal | Baths / Grooved Subfloor |
| 1/2" PEX | 0.475" | 280 ft | 0.92 gal | Joist Plates & Standard Slabs |
| 5/8" PEX | 0.574" | 380 ft | 1.34 gal | Shops / Barndominiums |
| 3/4" PEX | 0.671" | 480 ft | 1.84 gal | Commercial / Pole Barns |
Finished Floor Covering Temperature Limits
Why indoor wood/LVP floors require lower supply water than tile or carpet
| Floor Finish | Max Surface | Target Supply H₂O |
|---|---|---|
| Engineered Wood / LVP | 85°F Strict | 105°F – 115°F |
| Ceramic / Porcelain Tile | 88°F – 90°F | 110°F – 125°F |
| Bare / Sealed Concrete | 85°F – 88°F | 105°F – 120°F |
| Low-R Carpet & Pad | 85°F Surface | 125°F – 135°F |
Indoor Residential Subfloor & Concrete Slab Engineering FAQs
Key differences between heating a bathroom/kitchen over wood joists vs. pouring a garage slab
1. Why are stamped Aluminum Heat Transfer Plates mandatory for wood subfloors? +
Plywood and OSB subfloors are thermal insulators compared to concrete. Simply stapling PEX tube directly against the underside of a wood subfloor without aluminum plates transfers heat in narrow "stripes" and forces you to run dangerously hot water (140°F+). Snapping PEX into stamped omega-channel aluminum heat transfer plates spreads thermal energy laterally across the full 6-inch or 8-inch bay so the floor warms evenly with low 105°F–120°F water.
2. How do I protect Engineered Hardwood or LVP from warping over radiant heat? +
Engineered wood and luxury vinyl plank (LVP) warranties require keeping the finished floor surface below 85°F. Always pair a 3-way thermostatic mixing valve (to cap supply water around 105°F–115°F) with a dual-sensing hydronic thermostat that includes a 10k-ohm floor thermistor probe taped into the subfloor or tile mortar bed.
3. Why shouldn't PEX be routed under kitchen cabinets, islands, or toilets? +
Routing PEX under permanent toe-kick base cabinets or kitchen islands traps heat inside closed boxes—wasting boiler BTUs, drying out cabinet joinery, and warming stored food. In bathrooms, keep PEX at least 8 inches away from the toilet flange so radiant heat never softens the wax ring seal. Use our Unheated Footprint Deduction slider to subtract these fixtures automatically.
4. Can a single custom room (like a master bathroom) run on just 1 PEX loop? +
Yes! If your net heated area requires less than 200 linear feet of 3/8" PEX (or 280 linear feet of 1/2" PEX), the entire room can be heated with a single continuous serpentine circuit. Our BOM automatically switches from a multi-branch manifold to a compact single-zone / 2-port assembly when only 1 circuit is needed.