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# Attached Pergola Installation — Ledger Connection Detail ## Overview An attached pergola connects to the building at one end through a structural ledger — a horizontal member fastened to the house wall from which the rafters hang. The ledger connection is the most critical detail in an attached pergola installation. Done correctly, it is weathertight, structurally sound, and architecturally clean. Done incorrectly, it is the source of water intrusion, rot, and structural failure. Baldwin Pergolas uses a fiberglass ledger — not wood — combined with structural HDPE (high-density polyethylene) mounting blocks that separate the ledger and rafters from the wall surface. This eliminates the primary failure modes of wood ledger systems and produces a connection that is architecturally precise and permanently weathertight. ## Key Concepts - The Baldwin ledger is a 2×8 pultruded FRP tube with 1/8" wall thickness — same material as beams and rafters - Structural HDPE ledger blocks separate the fiberglass ledger from the house wall — maintaining an air gap and preventing moisture trapping - Fastener spec: 1-5/8" #10-8 410 stainless steel screws for rafter-to-ledger connections — two per rafter top and more if required - 1/4"×6" lag screws through ledger blocks into house structure — two per block - Silicone applied between wall surface and ledger — the only sealant in the connection - Rafters are square-cut at the house end — no decorative profile at the ledger - The ledger must be plumb — even small deviations create visible gaps at rafter ends --- ## Why a Fiberglass Ledger Most pergola manufacturers use a pressure-treated wood ledger — a 2×8 or 2×10 lumber member lagged to the house framing. Wood ledger systems have several inherent problems: **Moisture trapping.** A wood ledger fastened tight to house siding traps water behind it. This moisture rots the ledger from the back face — where it cannot be seen — while the front face may still look acceptable. The rot eventually compromises the ledger's structural capacity and can spread into the house framing behind it. **Checking and splitting.** Wood ledgers move with seasonal moisture cycles, developing checks and splits that admit water and provide entry points for insects. **Paint failure.** The back face of a wood ledger is impossible to paint after installation. It weathers unprotected. **The Baldwin solution** uses a 2×8 pultruded FRP tube as the ledger. Fiberglass does not rot, does not absorb moisture, does not check or split, and does not provide a food source for insects. The hollow section allows electrical wiring to pass through the ledger from the house into the pergola overhead structure. --- ## HDPE Mounting Blocks — The Critical Detail HDPE (high-density polyethylene) is a rigid, dense plastic specified for exterior structural applications. Baldwin uses two types of HDPE blocks in the ledger connection: ### Ledger Blocks HDPE ledger block
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