Chimney height on roof

I always thought a chimney needs to be at least 3 feet above a roof. But in looking closer at the Inspection Graphics it states a minimum of 2 feet for gas vent or type L vent. The chimney in the pixs is from the oil furnace and is 2 feet high. Is this OK or should it be three feet?

I measured it from the low side, but on the ridge side it is probably only a foot and a half tall. Should it be 2 feet at the ridge side?

Strictly speaking of the projection of the chimney. . .

3 ft. tall min - measured from the tallest side.
2 ft. higher than any wall/ridge within 10 ft.

Yes, minimum…

So, it’s too short on both sides. No difference from gas, oil, wood chimneys?

If it’s a “chimney,” those are the requirements. If it’s a “vent” (gas-fired, oil-fired), these requirements do not apply.

This is a metal chase surrounding a vent.
What say you?

Depends on the slope of the roof and the appliance it serves, but generally speaking for what is pictured. . .

2 ft. minimum projection from the roof and 2 ft. above a wall or similar obstruction within 10 ft. of the termination.

OK ,from the earlier response I thought you were viewing it as a wood burning fireplace chimney.

I think many are not clear on the difference and bet seeing the fake brick(metal) chase would put them in 10/3/2 mode.

Here is another pix. It is a vent from an oil fired furnace made to look like a brick chimney. So the 2/10/3 rule doesn’t apply? But it still needs to be at least 2 feet above the ridge.

That is pretty much what I was saying.

OK, anyone., what is the difference between these two. A block chimney with a tile flue from a gas furnace and this metal flue from an oil furnace. Why are the requirements not the same? One is required to be three feet high but the other one only 2 feet high? Am I missing something?

for O’Keeffe about false chimney.
Its a chase enclosure and there are plenty of them in western part of Montreal Quebec Canada.They can be for wood,an oil furnaces.Cheaper then doing a brick double width and single width Terra cotta lined chimneys.
You see them mostly on double cladded facade exterior homes.Lower part brick about first 8 to 10 feet and upper part siding.I rarely see this on fully brick clad homes but I have seen a few and far between.Maybe after thought.
For O’Keeffe on brick and block chimney.
Even the ridge vent is so close to the spark arrester from the chimney ,no crown to control rain dripping , and drafting ,stop spillage and if there is back drafting all that startup and shut down smoke goes right into the home along with Co’s from burning…
From the pictures I see its a real hazard.
Just my opinion.
Now to answer you question its fire hazard that is caused from wood burning fireboxes and fire places and the sparks on the roof from chimneys built to close to the roof that is why they have a hight restriction and should have spark arresters on top of the crown or cap as some people call it.The hight regulation is for smoke and spark that has to draft properly over a roof and not drift into windows and roof vents.As for oil stoves the heat is not as hazards and no sparks but there is Co’s that have to be carried away by drafting so hight requirements are in place.
If you google chimney hight requirements you should be OK and InterNACH has in depth building code on this.
Hight restrictions for oil and wood burning fireplaces.
1 : brick chimneys must be higher because of outlet is larger ‘’ FLUE’’ for spark and fire concerns
2 : oil chases lower because outlet is smaller ‘‘flue’’, no chance of spark fires.
I hope this helped you.
I am a mason and build chimneys and if you need more help email me and if I have the time I would be glad to answer you question but everything is on internachi .
Sorry if my explanation is all over the place .I am tired.

I am asking why are the height requirements different, or am I misinterpreting/misunderstanding something?

Both of these would be breaking code in Montreal Canada.Read hight and clearance regulations for chimneys.No more block chimneys in Montreal thats for most of the areas I have looked into anyway and the clearance is off spec that for sure.

“Chimneys” used strictly as vents are not the same as chimneys that are part of a fireplace system.

Oh the fog is lifting! A"chimney" used for gas or oil furnace does not need to be 3 feet high but a chimney used for a fireplace does. Both chimneys however need to be 2 feet higher than anything within ten feet.

Please look at the ridge and how close you are to the RIDGE VENT.Its a vent and can draw as well as expel air ,right.So back draft can cause low burn smoke to inter the attic.I see only 2 courses above the ridge.Thats 8 inches with the mortor bed.I also see bricks in need of pointing and for me what you see on the out side of the chimney there is 50 percent plus more decomosition going on inside.
Its a consern and needs a pro to give advice.

I agree, the block chimney condition needs to be addressed. I was using it here as a comparison to the other chimney, Mason vs metal. Thanks for your help. As a home inspector, a generalist, I try to use the 10/3/2 rule as a guide. I was looking for some clarification on the requirement.

Does not matter what type of fossil fuel is burnt and exhausted or which means of constrution are used the minimum clearance from the roof or other vertical walls is the same. The ICC has an easy formula to remember (3,2,10)

3’ at roof line and 2’ measured at 10’