New Construction: Hearth Extension - Masonry - Contractor Talk

New Construction: Hearth Extension

Thread Tools Search this Thread Display Modes
Old 11-07-2018, 10:20 AM   #1
Willin's Avatar
Trade: Retired
Join Date: Aug 2012
Location: Where it snows
Posts: 327
Rewards Points: 434

New Construction: Hearth Extension

A freestanding woodburning fireplace will be built in a new house. Fieldstone faced, faces greatroom, one can walk around all four sides.

Foundation below basement floor is a 'crete pad, and a 4 sided column of 6" CMU rises to the main floor. The hearth and fireplace construction begins at that level.

Rather than a cantilevered slab for a base for the desired hearth extension, can the 12" hearth be supported on the wood-framed floor structure?

The mason proposes to cover the floor structure with felt paper, then lay a course of CMU on that, and do a stone hearth finish atop that.
Willin is offline  

Warning: The topics covered on this site include activities in which there exists the potential for serious injury or death. DOES NOT guarantee the accuracy or completeness of any information contained on this site. Always use proper safety precaution and reference reliable outside sources before attempting any construction or remodeling task!




Old 11-07-2018, 06:21 PM   #2
fjn's Avatar
Trade: mason
Join Date: Aug 2011
Posts: 4,836
Rewards Points: 10,154

Re: New Construction: Hearth Extension

Can it be ? Of course. Is it proper ? H no !


fjn is offline  
The Following User Says Thank You to fjn For This Useful Post:
brickhook (11-15-2018)
Old 11-07-2018, 09:21 PM   #3
Fouthgeneration's Avatar
Trade: Masonry
Join Date: Jan 2014
Location: Mid west
Posts: 2,190
Rewards Points: 7,829

Re: New Construction: Hearth Extension

Every open/ glassed in face will need a inflammable surface for 18-24" from the face(s) of the fireplace.

Raised hearths are silly IMHO, they shrink usable floor space, you could use 1/2 arches that spring from the fireplace's basement structure + rebar.

Is the basement footing acting as the ash dump and cold air supply path???

Did you plumb in a gas pipe for use as you age? or in power outages???

Multi opening fire places rarely are very efficient.....

I'd want to see a near exact copy of the planned fire place that worked or a 200% guarantee/bond, money for DEMO and replacement with a working design in an occupied home
I might be an Idiot, but I know things that You don't: Please wait till after you get my know-how to insult me....
Fouthgeneration is offline  
Sponsored Links
Old 11-10-2018, 10:17 PM   #4
JBM's Avatar
Trade: Masonry
Join Date: Mar 2011
Location: Mass.
Posts: 7,582
Rewards Points: 8,326

Re: New Construction: Hearth Extension

If you formed and poured 10- 12" of concrete over the floor, with paper under it, its ok, kinda hack but its do able.

If it isnt continous into the firebox area, itll crack at the joint @ the hearth.
JBM is online now  
Old 11-11-2018, 06:52 PM   #5
Fouthgeneration's Avatar
Trade: Masonry
Join Date: Jan 2014
Location: Mid west
Posts: 2,190
Rewards Points: 7,829

Re: New Construction: Hearth Extension

Tact down METAL under the concrete, any cracks open up in the next 100 years the hot cinder lays on metal, not the wood subflooring.....

IMHO raised hearths are just a brain fart hanging around from 10 Cent tract homes of the late 40s - 60s. where they X-out the under floor hearth structure to save time/money...

Few rooms are large enough for center of floor fireplace IMHO. If yours is, go for it.

Is the stone work being used as "Trombe" heat storing wall?

Don't let a lazy mason,
((6" CMUs fpr 30' plus of fireplace-chimney?=cheesy)+ poured on top of basement slab footing???= double cheesy IMHO))

shrink your room up. And install a gas line and cold(unheated outside) air supply to the firebox to lower the cost of actually having a fire/flame in the firebox
I might be an Idiot, but I know things that You don't: Please wait till after you get my know-how to insult me....

Last edited by Fouthgeneration; 11-11-2018 at 06:57 PM.
Fouthgeneration is offline  
Old 11-20-2018, 11:24 PM   #6
jomama's Avatar
Trade: Concrete & masonry
Join Date: Oct 2008
Location: Wisconsin
Posts: 884
Rewards Points: 134

Re: New Construction: Hearth Extension

Cantilevered hearths have worked for decades w/o issue if done decently. Laying masonry over (presumably) OSB subfloor has a less stellar track record. Not sure this is the place you want to cut a few dollars out on an otherwise expensive fireplace..........


jomama is offline  
The Following 3 Users Say Thank You to jomama For This Useful Post:
fjn (11-21-2018), Fouthgeneration (11-21-2018), stuart45 (11-23-2018)

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

Similar Threads
Thread Thread Starter Forum Replies Last Post
Commercial Construction NJ IM Contracting New Member Introductions 1 07-23-2015 06:37 PM
Construction Project Design Criteria rpurnell General Discussion 4 04-07-2013 09:25 PM
Extension Cord Deal GRB Tools & Equipment 6 05-30-2012 07:33 PM
Did you know Microsoft has Financial and Operational Software for Construction bdupper Accounting Software & Discussion 0 06-12-2009 08:25 AM
Construction vs. Manufacturing. Who wins? poole_3 General Discussion 10 04-04-2009 07:51 PM

Join Now... It's Fast and FREE!

I am a professional contractor
I am a DIY Homeowner
Drywall Talk is for

At we cater exlusivly to professional contractors who make their living as a contractor. Knowing that many homeowners and DIYers are looking for a community to call home, we've created DIY Chatroom is full of helpful advices and perfect for DIY homeowners.

Redirecing in 10 seconds
No Thanks
terms of service

Already Have an Account?