clearance to fireplace opening fireplaces hearth extensions specs of add hearth extension pad canada wood stove hearth extensions author reuben saltzman structure tech home inspections fireplace building regulations custom wood fireplace mantels manufactured to your specifications included below are a few photos showing diffe fireplace hearths along with my commentary on what makes them acceptable or not fire ribbon direct vent single vu combustible clearance fireplace option 1 pre fabricated masonry