What is cladding and what do you mean by the whole assembly? I have now heard twice from Bluestar that tile can go directly on Sheetrock...

If you want to use island trim in front of your back wall the entire wall is required to be fireproof-ie tile on concrete board attached to fireproof steel stud wall and concrete board on the rear side of the stud wall. To avoid needing a fireproof wall assembly, you could pull the gas range out 8"minimum from back wall-might vary with range but no gas range with island trim can be closer than that to combustible wall-wood studs-check with your fire/building inspector- OR you could use one of the taller backguards which I believe usually come in 8", 12", or 24" heights and have a 1" air gap between the stainless steel face and your back wall which prevents pyrolysis of your sheet rock and wood wall studs. Pyrolysis is the condition whereby repeated low level heat exposure of combustibles-your sheet rock paper and wooden studs, despite being covered with tile- results in the lowering of the required temperature to self ignite of those combustibles at a future exposure of low level heat.

The Bluestar guy is not a building engineer nor a fire prevention officer.

Understood. So is this a requirement by code, since not a requirement of the manufacturer?

If the range is pulled out about 4” from the wall, is the fireproofing behind the range still needed or is tile on drywall fine?

It is required by the manufacturer. Here is the wording exactly from the installation instructions:

”If you are using an island trim or grate height, a six inch clearance between the back of the range and a combustible surface is required. If an island trim is to be used without this six inch clearance, the back wall must be constructed using non-combustible and heat resistant materials that extend below the top surface of the range a minimum of six inches.“

It specifically says the back wall must be constructed using non-combustible materials. Putting tile on a wall does not make it non-combustible.

I understand. I guess Bluestar itself is interpreting “non-combustible” materials to include tile on drywall, and telling that to its customers.

The source of these rules is the International Mechanical Code, Table 308.4.2 and its corresponding numbered paragraph. From there, they are adopted into the International Residential Code; see subsection M1306.

Follow up question: we have four inches of space between the back of the range and the wall. Is that size gap plus tile on drywall ok, or still need

Still need cement board instead of drywall?

You and your code enforcement officer may wish to interpret this table. Combinations not listed would require engineering analysis of thermal conductivity to the combustible materials behind them, and agreement on acceptability by code enforcement. Code enforcement officers have the power to reject deviations no matter what you prove by analysis to be safe if not compliant with code or with the manufacturer's installation instructions, and I assure you that rejection is the easy way out. Any deviations have to be tolerant to new owners making changes without knowing what limitations might have been imposed.

It’s very odd to me that bluestar itself, our code official, and salesperson are all saying tile on drywall is fine. If I had never come across Houzz I’d have never known!

I believe @vinmarks earlier in this thread provided the relevant paragraph from the manufacturer, which seems to me to be consistent with the code: Tall backguard, no gap; low or no backguard, gap or rebuild wall.

If you are desperate for no gap, then try this: Extend the counters 6 inches from the wall, and set the range to be 6-inches from the wall, then all you need is a surface behind the range for looks. If you adopted real stone for your counters, I think it would be OK for continuation across the gap. Essentially, the stone would act as the first six inches of the counter of an island installation. I am unclear about this range's need for venting of internal parts, so that would have to be accommodated.

Obviously, the hood would have to be built out also, or made larger, front to back. Any island or peninsula opposite the range would have to be moved if the gap between counters became too tight for easy personnel movement.

Thanks, though we’re not doing a full reno. Just hoping to tile behind our range, which already sits 4” (not 6) out from the wall. Just wondering if that gives me enough safety with just tile.

As vinmark stated several posts above quoting from the install instructions 6 inches, not 4 inches is required-so No, 4 inches does NOT give you enough? Safety, 6 inches does, there is no negotiating/modifying that, perhaps the easiest way forward is to use the 6 inch backguard and enjoy the pro look, my sister's gas range came with the 6 inch back guard preinstalled, looks great

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A combustible surface is anything that can burn (i.e. sheet rock, wall paper, wood, fabrics etc.). These surfaces are not limited to those that are visible and also include materials that are behind non-combustible materials. So if you have tile with sheetrock or other combustible material behind the tile the range must be 6 inches from it if not using a back guard.

There isn't a table entry for that configuration, so I can't say whether it is safe. It isn't to code, however.

I don't think the tile does anything to avoid pyrolysis. If you could depend on a flow of cool air up the back and along the wall to the hood, for example from a make-up air source, that air might keep the wall cool. But such an air source requires an active MUA that is somehow tied to the range operation, along with a hood tied to the range operation. Heat sensors might be involved. The cooling would have to be automatic and reliable, and not under the control of the occupants under normal circumstances. You might imagine why such a scheme is not included in the table -- the amelioration schemes of the table are passive, reliable, and difficult to bypass.

We just ordered a 36" Bluestar cooktop (not the rangetop) -- is the same backsplash guard required for the cooktop? I don't recall seeing any such requirements in the brochure but I could be mistaken.

Again, please download the installation manual for the cooktop and read it carefully. If you install according to the manufacturer's instructions, you should pass inspection, and most importantly, you have not given your insurance company a reason to exclude some or all of the cost of rebuilding your residence, should a fire occur.

On that thought, it occurs to me that if one wanted to know what an unapproved but perceived as sufficient protection scheme would accomplish, pyrolysis-wise, embedding a series of thermocouples on the cooktop side of the first inflammable layer before tiling or whatever and then measuring temperatures with various cooking conditions might provide peace of mind, or might provide sufficient alarm to motivate accepting the rules for what they are.

One would like manufacturers to perform this task for whatever conditions their sales people are touting, and then get UL approval if the data are favorable.

Page 4: If installed in a countertop along a wall at the rear the surface must be inflammable material extending at least six inches upward.

https://www.bluestarcooking.com/wp-content/uploads/2016/05/BlueStar-DropIn-Cooktop-Manual-3.29.19.pdf

Ack - thanks! Didn't notice that before -- unlike the rangetop manual, they don't really highlight the need for a backguard in the cooktop manual. Any thoughts on where to find a 6" tall backguard?

It's a little puzzling because the bluestar manual also says:

The non-combustible material need not extend horizontally past the initial barriers thickness. The initial barrier should consist of materials such as ceramic tile, cement backer board, stainless steel (.032” Thick) or other non-combustible material. Non-combustible materials are defined as non-combustible as in the form in which the material is used and under the conditions anticipated, the material will not aid combustion or add appreciable heat to an ambient fire or materials that are in compliance with ASTM E 136. Refer to the appropriate installation manual and/or local building code for additional information.

I'm not really sure what to make of all of this. Considering adding a 6" backguard to our RCS range, which has tile behind it. But I'd rather not.

You need a backguard against a wall. Period.