Local gas fireplace installation in Sandalwood

Supports, thimbles and firestops

A vent run needs support along its length, at the spacing the manual sets, so joints do not pull apart over time. Where it passes an outside wall, a wall thimble or firestop from the vent maker holds the pipe centered and keeps its clearance to the framing. Where it passes a ceiling or floor, a firestop spacer does the same job.

Horizontal pipe keeps the clearance the manual lists, which on some systems is larger above the pipe than beside it. Air spaces around the pipe stay open, with no insulation packed in. Joints are locked as the vent maker's instructions show.

A vertical termination through the roof

When the vent goes up instead of out, it climbs up past the ceiling and across the attic to a vertical cap, which stands as high above the roof as the manual requires for that roof pitch. The penetration is sealed with the roof flashing and storm collar that come in the vent kit, fitted as its instructions show. Around them, the roof covering itself may need sealing and patching, and we name the trade that does it. In the attic, the pipe keeps its listed clearance to framing and insulation, with the shield the vent maker supplies.

Reading the mantel chart

A combustible mantel above a gas fireplace follows a chart in the manual that pairs the mantel's depth with the minimum height above the opening. The deeper the shelf, the higher it has to sit. Trim that stands out from the facing beyond a small set distance is treated as a mantel under the chart, so a thick molding counts.

Some makers offer mantel packages already tested for their units. We mark the chart height on the framing so blocking goes in at the right level, and check the mantel you choose against it. The chart says where its measurements start, and we measure from the same point.