The Harvia WHM24 rain collar (Harvia part SPWHM24, “rain flange, symmetrical, black”) is the rubber weather seal for Harvia steel chimneys on flat roofs and barrel saunas. The symmetric boot fits around the insulated chimney casing at a horizontal roof surface and seals the lead-through against rain, snowmelt, and wind-driven water. Order it as a replacement if the collar supplied with your chimney kit is worn or damaged.
Features
- Genuine Harvia rain collar (SPWHM24) for steel chimney kits
- Symmetric profile for flat roofs and barrel-sauna roof plates
- Black rubber construction seals around the chimney casing
- Keeps the roof lead-through weather-tight
- Limited 2-year warranty (consumer use); limited 1-year warranty (commercial use)
What’s Included
- Rain collar, symmetric
Specifications
| Model | WHM24 (Harvia SPWHM24) |
| Material | Rubber |
| Color | Black |
| Roof type | Flat roofs / barrel saunas |
| For use with | Harvia steel chimney kits |
Compatibility
Replacement for the symmetric rain flange used in the WHP-ASSYM / WHP-ASSYMM roof accessory kits and WHP1000500 packages for the Harvia WHP steel chimney system. For pitched roofs, use the WHM22 tilted rain collar instead.
Note: as a manufacturer replacement part, this item is not returnable — to preserve the originality, operation, and safety of replacement parts.
Good to Know
Is this the right collar for a barrel sauna?
Yes — barrel saunas vent through a flat roof plate, which takes the symmetric (WHM24) flange. The WHM22 tilted flange is for pitched roofs.
Do I need sealant to install it?
Yes — Harvia’s chimney manual calls for silicone beneath the flange, closely spaced roof screws (max 35 mm apart), and a fully tightened clamp so there are no gaps in the seal.
Designing a Harvia Chimney System
Every part on this page belongs to Harvia’s modular WHP steel chimney system: a 115 mm (4.5″) smoke path inside a 220 mm (8.6″) insulated casing, assembled with slot-and-lock joints. Here is how a complete system comes together:
- Start with the chimney. For pitched roofs, the WHP1500 kit (1500 mm chimney plus rain cap, tilted rain flange, smoke pipe, and ceiling lead-through set) is the core of the system. For flat roofs and barrel saunas, the WHP1000500 package bundles the chimney with the symmetric roof kit.
- Connect the stove. Bridge the stove collar to the insulated chimney with 115 mm WZ smoke pipes (20 cm, 50 cm, or 1 m). Add the WZ115030SP damper plate at the stove to control draft while firing, a WZ115120 reducer where pipe sections step down, or the WZ115155 adapter if you are transitioning to 6″ US Class A pipe.
- Reach your height. Add WHP500 (500 mm) or WHP1000 (1000 mm) extensions. Stay within Harvia’s limits: 5.0 m (16.4 ft) total chimney height, no more than 2.0 m (6.5 ft) above the last support, lateral supports every 3.0 m (9.8 ft).
- Go through the roof. Choose the roof kit that matches your roofline — WHP-AS for tilted/pitched roofs, WHP-ASSYM for flat roofs and barrels. Replacement rain collars: WHM22 (tilted) and WHM24 (symmetric). Add a snow barrier above the chimney where sliding snow can load the flashing.
- Seal and control. The WHM25 vapor barrier restores the vapor-tight layer where the chimney passes the sauna ceiling; the WHP270 insulated damper closes the flue after the fire is fully out so the sauna holds its heat.
- Finish the stove side. Stone-filled covers — WL300 for Legend stoves, WL300PC for Cilindro — absorb radiant heat from the smoke pipe and significantly reduce its required safety distances.
Key clearances and rules: vertical installation only; 100 mm (4″) from the insulated casing to combustibles; 500 mm (stainless) or 375 mm (black) from non-insulated smoke pipe unless shielded; designed for wood-burning stoves in standalone outdoor sauna buildings. Confirm your plan with your local building authority — and if you would like help speccing the system, talk to us; we design these daily.
Shop the Complete Harvia Chimney System
1. Start with the chimney
- WHP1500 Chimney Kit, 1500mm (stainless or black) — the system core
- WHP1000500 Complete Chimney Package for flat roofs & barrel saunas
2. Connect the stove
- WZ Smoke Pipes, 115mm (20 cm / 50 cm / 1 m, stainless or black)
- WZ115030SP Stove-Side Damper Plate (draft control while firing)
- WZ115120 Reducing Pipe (joins mismatched pipe sections)
- WZ115155 Adapter, 4.5″ Euro to 6″ USA (hybrid Class A transitions)
3. Reach your height
4. Go through the roof
- WHP-AS Roof Accessory Kit for tilted / pitched roofs
- WHP-ASSYM Roof Accessory Kit for flat roofs & barrel saunas
- WHM22 Replacement Rain Collar, tilted roofs
- WHM24 Replacement Rain Collar, flat roofs & barrels (this page)
5. Seal and control
- WHM25 Chimney Vapor Barrier (seals the ceiling penetration)
- WHP270 Insulated Smoke Damper (retains heat after firing)
Prebuilt
Sauna Brushes
Vents