Fireplace Construction and Drafting

Introduction

How many of you have a fireplace in your home?

Is it your major source of heating? Fireplaces today are more of a luxury item

– major element of interior design in living area» provide atmosphere

– minor concern for heat

Fireplace Design and Construction

Topics of Discussion– Type and style – Structural framing around fireplace– Size & type of opening– Chimney design/height above roof– Fireplace terminology/function– Flue sizing– Fireplace drawings

Common Fireplace Types1--Single faced

flush hearth

raised hearth

2--Double faced

interior corner designs

projecting corner

opposite sides design

3--Three faced

4--Free standing

Double Faced Fireplace Example(Projecting corner)

Double Faced Fireplace Example (Opposite Sides)

Three Faced Fireplace Example

Structural Framing Requirements

No wood or combustible material is allowed to touch any part of the fireplace, its foundation, or chimney– 2” clearance usually required by code

No structural piece should rest on the fireplace and use it as support

Structural Framing

Note– double headers

& trimmers

– opening < 10’

– ledger strip or Joist hangers

fireplace & chimney free-standing & self-supporting

(from FP below)

(or Joist hangers)

Flashing around Chimney

–A type of flashing at chimney--saddle or “cricket”--diverts water away from behind the chimney

Drawing callout: 26 GA GI FLASHING

Note

–General flashing

»

Chimney Heights Building Code: (2 foot 10 foot rule)

– Chimney 2’ minimum above any construction within 10’ of the chimney

Chimney Flues

Area through which the combustion gases and smoke travel

Flue liners– used to prevent deterioration to mortar joints– produces a better downdraft & requires smaller

flue (smoother surface) Unlined Flue

– Chimney must be thicker walls than with chimney with flues liners

Chimney Flues

Each fireplace requires a separate flue– may be contained within same chimney– minimum of 4” distance apart– must be different heights, min of 4” from top

4” Min

Chimney Cap

– keeps water away from lining

Spark Arrester– screen device that

prevents sparks from leaving the chimney & passing onto the roof

Fireplace Terms1. Firebox--opening 8. Damper--

2. Hearth--min 16” sizes vary

prefered 20” 9. Throat

3. Ash dump 10. Smoke

4. Ash pit chamber

5. Clean out 11. Smoke

6. Steel angle or lintel shelf

7. Mantel 12. Flue

13. Chimney

Fireplace Terms

FireplaceFunction

Damper1. Controls air flow/shut off when not in use

Smoke Chamber

1. Transition from the firebox to the flue

2. Responsible for controlling & regulating burning and eliminating smoke & combustion gasesSmoke Shelf

1. Prevent downdraft

2. Help divert cold air into smoke chamber

Throat

1. Channels smoke into chamber

Flue Sizing

Crucial that fireplace opening be in proper proportion to flue for proper operation

Inside free space of flue called effective flue area, expressed as fraction

Effective flue area (EFA)– 1/10 minimum allowed (10%) of fireplace

opening– 1/8 preferred (12%)

Flue Sizing Find affected firebox area

– based on type of fireplace– Single faced

» Area = h (x) w

Multiply by Ratio– if 30” wide x 26” high

– Area = 30 (x) 26 =780 sq in

– Effective Flue Area (EFA)

– (Considering Min EFA 10%)

– Therefore 780/10 = 78 sq in

– See tables to select proper flue

Dbl-faced Area = 2(h x w)

Area = 2(w x h) + d x h

Area = h x w

Flue Shapes, Sizes, and Areas See Text for similar table to the table below showing flue lining sizes, etc.

Table relates only designs for 10% EFA, flue areas are okay

Flue Sizing find width at

bottom find height at

left find

intersection find nearest

curve above intersection

Fireplace Drawings

Required Drawings (see by code or city)– Enlarged Plan view

» like the floor plan but to include dimensions to build

– Vertical Section» shows all vertical relationships including dimensions

– Elevation of Fireplace front view» shows what the fireplaces looks like when finished

– Common scales: 3/8” = 1’-0” and 1/2” = 1’-0”– Views are arranges by orthographic projection

» height and/or width must align from view to view

Fireplace Drafting Layout

Fireplace Assignment (w)