How high should your chimney be with a woodstove?  Well did one yesterday; and as soon as I got out of vehicle I said chimney may be too low.

Well, they had a WETT Inspection from a local Midland area inspector who showed the chimney as being compliant apparently for their insurance company.

Pulled out my TruPulse laser height measurement tool – and with a quick measurement it showed 2 feet from where chimney exited roof to the top of the liner.

Now other company likely did not get onto the roof and perform a measurement and likely did not have a laser height measurement tool.  As far as I know there are no other Chimney Sweeps or individuals doing WETT Inspections in Simcoe County who have one – certainly not in North Simcoe / Midland / Penetanguishene area.  Wish I had taken with me sweeping yesterday in Blue Mountains though – a chimney clearly too low which a Collingwood company had pointed out to homeowner.   I clearly was visually; looking out approximately 10 foot range (guessing by eye) the top of chimney was essentially level with the roof at that point.

People wonder why or how a chimney can be in place for years and then be suddenly non-compliant.  Especially when they have had previous inspections done by WETT Certified individuals who say it is okay!?

Problem is a WETT Level 1 inspection is visual in nature; many/most do not venture onto the roof and none that I am aware of have capability to actually measure the height from the ground.  Yes it is not inexpensive – bought mine half a dozen years ago – but they have not come down at all in price!  Here is place to buy one if interested.  Below is video showing one being used.

So bottom line if the WETT Inspector does not get onto the roof; and does not have technology to measure the height of chimney; how do they know?

So some even ask when the code changed.  Or how it has been okay for this long?  Well the simple reason it has been okay is again nobody measured it – or simply overlooked it as they could not be certain.

The actual Ontario Building Code states:

9.21.4.4. Height of Chimney Flues
1) A chimney flue shall extend not less than
a) 900 mm above the highest point at which the chimney comes in contact with the roof, and
b) 600 mm above the highest roof surface or structure within 3 m of the chimney.

These rules have been in place for a long time.  There is no reason or excuse why any previous WETT Report would not pick these items up.  At minimum anybody who did these on regular basis you would think would notice immediately from ground when driving into the laneway – as I did. A Home Inspector who also does WETT Reports may miss this; as they realistically do not do enough of this work to necessarily pick this up.

Those who are thinking of building their own chimney (be it masonry or factory built (stainless steel) – follow the code.  Some may have trouble grasping the measurements – however the picture above should help.

These measurements are to not only meet code, but the wood burning appliance will operate better and often cause less problems.

Essentially the rule states the chimney must be 600mm (2 feet) taller than any structure within 3 m (10 feet) of it and at least 900mm (3 feet) taller than the roof where it exits/penetrates the roof.  c

These as mentioned are designed to ensure proper draft at fire as well as reduce likelihood of house fire.

A chimney which is too low or close to the roof (less than the necessary 300 mm height) is more likely to cause a roof fire from flying sparks and less likely to draw well.

It should also be noted that as a rule the minimum total length should be no less than 15 feet, this is the height the wood stoves are tested and certified at.  Note this is 15 feet from top of chimney (where smoke exists) to the floor on which the wood stove sits.

On the other side of the coin, too tall of a chimney can result in over drafting which can in fact cause damage to some appliances.  Now some manufacturers do offer dampers in double wall stove pipe – but must be used with care.

However a good inspector should not need to go onto the roof to identify some chimney defects; one that is too low is one of these.  You can recognize some problems as soon as you arrive – if you are luck enough to have a high precision laser height measurement tool then that works as well.  There are other defects I will grant you that are more difficult; I did one in Port McNicol earlier this year that the fire department said was okay – however the chimney was too high and actually should have had braces/support down to the roof.  Why did they pick this up?  Likely two reasons – first the fire departments in townships are likely volunteer and not as experienced with this work as those who do it full time – secondly they did not go onto the roof for a real measurement.

Bottom line – best to consult a professional if working on building a chimney!  This becomes particularly so if your property is near different terrain which maybe be near high hills; higher elevations or even out on a lone island in Georgian Bay – requirements may vary slightly.