Gas fireplace venting from a family-owned team in North Quarter

Firestops on a B-vent run

B-vent passes through ceilings and floors with a firestop at each framed level. One B-vent fireplace manual sends the installer to the vent maker's instructions for firestop sizes and notes that only one firestop is needed per frame.

The same manual asks installers to avoid cutting load-bearing framing to make room for the vent. Our crew checks each firestop it can reach and flags any framing that was cut, since a structural fix is separate work and is quoted on its own line.

Two fireplaces and two caps on one wall

Homes with two gas fireplaces sometimes end up with two caps on the same wall. One maker asks for at least 3 feet between termination caps and gives a table for caps grouped in an alcove.

Each fireplace also needs its own vent system from end to end. Our specialists check both runs, measure the spacing between the caps and write up each fireplace separately so you can see which one needs what.

Why a B-vent loses its draft

Poor draft has a long list of venting causes in one B-vent fireplace manual, and each one points at a different repair. Our pros work through it in order, since the fix for a short vent is nothing like the fix for a blocked one.

The list below comes from that manual. Several causes can exist on the same house, which is why we check them all before quoting.

• Too much offset or too many elbows
• A vent that is too short or too close to the roof line
• A blockage restricting the pipe
• The wrong vent type or the wrong size
• More than one appliance on one vent

Power for fans and electronic ignition

Many direct-vent fireplaces need electricity for a blower, lights or electronic ignition. One manual requires the appliance to be grounded under local codes, falling back to the National Electrical Code where no local code applies.

Any new outlet or circuit belongs to an electrician and shows up as a separate line on your estimate. Our crew checks that the fireplace's power connection is in place and explains what the manual asks for before any vent work is scheduled.

Places a gas fireplace cannot be tucked into

Built-ins and closets are tempting spots for a fireplace in a remodel. One direct-vent manual states that its appliance is not approved for closet or recessed installations, and every manual sets its own framing and clearance rules.

Before a fireplace is moved into a new alcove or cabinet, our specialists compare the plan with the model's framing drawings and the vent route it would need. The written estimate covers both, so the design works on paper before anyone builds it.