In coastal construction, old ways often really are better ways. As we build four fireplaces in our Nantucket project house, it's nice to talk about a category that's improved by new approaches. Early masons didn't have the advantages of weather-sealing products, concrete blocks, and specially designed flue liners. Yet some time-honored considerations remain.
Instead of serving as primary heating systems, fireplaces now offer other comforts. In places like Nantucket, tradition makes them obligatory. But having a fireplace means poking a hole in your roof and adding to maintenance responsibilities. In other coastal locales, you might be better served with a different focal point, such as a window with a great ocean view.
The local angle
Trust techniques that have stood the test of time. The fireplace designs for our project house are similar to those in area homes dating back a century or more. Local masons are intimately familiar with them. This expertise reduces the likelihood of smoke problems at the fireplace level and water damage where chimneys meet the roof.
One common approach in Nantucket involves installing a lead shelf within the chimney a few courses above the roofline. During heavy coastal storms, the shelf provides extra defense against windblown rain, which can penetrate upper-level chimney bricks and cause leaks below. Water absorbed by bricks drains onto the interior shelf and escapes through "weep holes" left between bricks.
Keeping it simple
It's possible to run multiple fireplaces into a single chimney. But each fireplace must have its own route through its own flue liner (a ceramic pipe with an opening proportionate to the size of the fireplace). Old fireplaces fed into a single flue, increasing fire and smoke hazards. The straighter the line smoke follows from the firebox to the chimney top, the better.
The same rule of simplicity applies to the correlation of the width, depth, and height of the firebox; the opening of the throat to the flue; and the flue liner diameter. Keeping those elements in proportion to one another minimizes danger and maximizes efficiency.
Combine traditional savvy with modern building methods and you'll ensure your home fires stay where they belong―in the fireplace.