NFPA 211 Protected Surface using ceramic tiles

[mother of the boots]

Hello! I am new to the site - and new to heating with wood.

We are close to purchasing a Jotul F100 to heat our less than 600 sq ft area. Due to space limitations we will need to use an NFPA 211 Protected Surface on the walls to reduce clearance. I would like to use ceramic tile and understand the part about the 1 inch air space behind the cement board.

Can one of you help me understand the part about the top and bottom air gap? Does that mean that we will be creating tile "panels" that float out from the wall with a visible gap behind them?

Thank you for sharing your knowledge.

 

[DAKSY]

Not sure what you mean about floating panels.
Basically, if you install some steel 2x4 studs with the
3-1/2 wide surface towards the wall or tile & mount the
hardibacker or Durarock onto those flat surfaces, you will leave
a 1-1/2" airspace between the backer & the combustible wall.
You have to leave a 1" airspace top & bottom so that the convection
air can & will dissipate any potential heat from the combustible wall.
You can trim out the edges with more backer & tile, but you MUST
leave the convection air space.

 

[begreen]

Hello! I am new to the site - and new to heating with wood.

We are close to purchasing a Jotul F100 to heat our less than 600 sq ft area. Due to space limitations we will need to use an NFPA 211 Protected Surface on the walls to reduce clearance. I would like to use ceramic tile and understand the part about the 1 inch air space behind the cement board.

Can one of you help me understand the part about the top and bottom air gap? Does that mean that we will be creating tile "panels" that float out from the wall with a visible gap behind them?

Thank you for sharing your knowledge.

Welcome. Yes, that is essentially correct. The objective is to allow air to easily convect behind the wall shield (panel). The wall shield panel is held one inch off the wall by spacers. The wall shield must be non-combustible, held 1" off the floor and open at the top. It's ok if the sides are closed off with trim. The spacers should be none combustible. They make ceramic spacers for this purpose or you could make them out of copper pipe, washers, or us doubled up, long 3" wide strips of 1/2" cement board.

https://www.hearth.com/econtent/index.php/articles/stove_wall_clear

 

[mother of the boots]

Thank you both. It sounds like I need to have 1 inch deep open space running along the top and bottom edge of the protected surface, but that I could trim out the sides. I'll have to try to figure out some way to "finish" that top edge so that it looks ... finished.
I appreciate your help.

 

[Highbeam]

It won't get you anything unless your F100 actually identifies a wall shield and provides reduced clearance requirements in the owner's manual. Is that the case?

For example. My stove has a minimum 7" clearance to combustibles in the rear. That's great. Adding an NFPA wallshield will not reduce that 7".

 

[begreen]

Check the manual for the stove. It sometimes is not next to the clearances chart. For the Heritage it is on page 6 at the top:

Clearances To NFPA 211 Protected Surfaces
You can reduce the clearances to combustible surfaces by
using any National Fire Protection Agency (NFPA)
approved wall protection system. Please refer to NFPA
211 for specifications and complete details. You can
obtain this information directly from NFPA.
National Fire Protection Agency
Batterymarch Park
Quincy, MA 02269
1-800-344-3555
1-617-770-3000

Likewise for the F100. The statement is on page 10 and the clearance chart is on page 12:

Wall-Mounted Protection: When reducing clearances
through the use of wall mounted protection:
In the U.S. refer to NFPA 211, Standard for Chimneys,
Fireplaces, Vents and Solid Fuel Burning Appliances,
for acceptable materials, proper sizing and
construction guidelines.
In Canada, refer to CAN/CSA-B365, Installation Code
for Solid-Fuel Burning Appliances and Equipment,
also for acceptable materials, proper sizing and
construction guidelines.

 

[Highbeam]

Neither of those C&Ps; describes how the stoves minimum clearances may be reduced. Proper wall shields are a great safety addition, but unless specifically addressed in the installation manual they are a belt and suspenders approach. Not gaining anything for the installation. I recall one scandinavian type stove maker that allows a wall shield to reduce clearances since they didn't offer a metal shield on the stove.

 

[begreen]

The NFPA 211 guide determines the clearance reduction in % depending on the construction of the shield. A full 3.25" brick shield = 33% reduction of posted clearances, a ventilated nc shield = 66% reduction. This can make a big difference when space is tight or with a stove that has large clearance requirements.

https://www.hearth.com/econtent/index.php/wiki/NFPA_Wall_Clearance_Reductions/

 

[Highbeam]

Those % reductions are based on the default 36" correct? Meaning the best you can do is a 66% reduction to 12"? I do not believe that the % reduction can be applied to the stove manufacturer's minimum clearance to combustibles.

These wall shields don't do anything for most modern stoves.

 

[begreen]

My understanding is that they are not just based on 36", they can be applied to the manufacturer's tested clearances. In the case of an unlisted stove they provide the clearances in a table. Otherwise the clearance reduction is based on a percentage depending on the construction of the shield. That's why the information is included in the manuals of many modern stoves. If the manual says you can apply the NFPA 211 rules for clearance reduction (as for the Jotul F100) then it applies to this stove.

 

[Highbeam]

Just think, I could stuff my heritage 2.3" from the wall. With more than half of that 2.3" consumed by the NFPA wall shield. And since clearances are measured from the stove body, the actual legs of the stove would be slammed up against this heat shield if not the combustible wall. Doesn't seem right.

 

[begreen]

For some stoves with good clearances it does get a little silly to try and reduce them. But for stoves with large clearances, it can make a nice difference.

 

[stoveguy2esw]

teh chart gives a percentage as well as a measurement , my understanding is that you can gainthe percentage or as close as the minimum clearance , but if your clearace is already at or inside the minimum clearace you do not get any closer

in other words , if you choose a method which allows 66% or 12" and your stove's listed clearance is ALREADY 12 inches you do not move closer even with wall protection

 

[begreen]

Mike, you are correct and I am wrong. Thanks for the clarification and apologies to Highbeam for my confusion.

That said, although I believe in honoring code, I think this rule is bunk. If a stove has a minimum of 12" clearance and you want to reduce that to 6" with a wall shield, it should be acceptable. The temp behind the wall shield will not get a lot above ambient and the combustible surface behind will be very well protected.

 

[Highbeam]

Hello! I am new to the site - and new to heating with wood.

We are close to purchasing a Jotul F100 to heat our less than 600 sq ft area. Due to space limitations we will need to use an NFPA 211 Protected Surface on the walls to reduce clearance. I would like to use ceramic tile and understand the part about the 1 inch air space behind the cement board.

.

So now I am concerned with the OP. Seems she "needs" or is using the NFPA reduction to go to a smaller clearance than the Jotul stove allows. This has the potential to put her out of compliance with code on the install.

With few exceptions, whenever someone builds a NFPA shield they are either being ultra safe or are doing something illegal.