PROSAUNAS Alder 1X2 SI Inside Corner Trim – Sauna Wood

Here’s the thing about inside corners: the cladding never terminates cleanly on its own. Tongue-and-groove boards meeting at 90 degrees need something to cover the joint, and that something is this. Skip it and the corner looks like a job site. Add it and the room closes.

The alder SI inside corner trim is a simple L-profile, 0.55" by 1.18" (14mm x 30mm), designed to sit over the ends of cladding boards where two walls meet at an inside corner. It’s narrow enough to look intentional, wide enough to cover a range of rough endings. Natural alder, same species and tone as the rest of the ProSaunas alder family, E1 certified, milled in Estonia. At $1.36 per linear foot, it’s the least expensive piece in the line.

Why Alder

The main job here is matching. If your walls are alder Grace cladding, your corners should be alder too. The warm reddish-brown, fine grain, and pleasant texture make it an intentional part of the room rather than a contrasting fix. Alder doesn’t overheat, doesn’t bleed resin, and E1 certification means no off-gassing concerns in a hot, enclosed space. The honest note: at this thin section (0.55"), it’s purely a finishing piece. It won’t structurally reinforce the corner or protect against hard impacts. Install it after the cladding is complete and dry-fit before fastening.

Specifications

• SKU: PS-ALDER-1X2-INSIDE-CORNER-TRIM-SI
• Species: European Alder (natural)
• Profile: SI inside corner trim
• Thickness: 0.55" (14mm)
• Width: 1.18" (30mm)
• Available lengths: 1 ft, 8 ft
• Price: $1.36 per linear foot (MAP)
• Made in Estonia by ProSaunas
• E1 certified, ultra-low emissions

Where it goes

Inside corners where two cladded walls meet. Plan one run per inside corner from floor to ceiling. Pairs with the VA outside corner trim, UK door trim, and 2×2 S4SEE moulding for a complete alder trim package. Finish the corner before any benches are installed so you have clean access to run the full length.

Shipping and samples

Sold by the linear foot. Flat $795 freight to the continental US, or free with a heater order. Free samples available: text your name and address to (844) 565-1113.

Call Ben² at (844) 565-1113 if you’d like to talk through the board count before you order.