Radon mitigation


My local AHJ is demanding radon mitigation pits for the "possibility" there may be an issue "one day" in all our commercial projects.  Its crazy, in a shop with 6 pull through bays there is not going to be a build up of radon gasses.  

I think the lobbyist are out of control on this one.

Dec 12, 18 4:16 pm
Non Sequitur

I've seen a big increase in radon products & presentations in the last 2 years... as well as heavy marketing in all those dumb do it yourself home renovation shows.  My codes require passive radon mitigation in crawl spaces... which is easily achieved by placing a grille in the wall.

Dec 12, 18 4:29 pm

I live in an area of Canada that Radon is not an issue. Its stupid. Even after presented with a standata that states its up to the professional to decide.

Non Sequitur

Are they asking for mechanical mitigation?


No, they approved plans, now are coming back after the slab is poured wondering were is it. I agree its just a pit with poly, crushed fill and a pipe, but the slab has already been poured.


On a 6 bay pull thru shop with slab on grade and the office portion on a structural slab.

Non Sequitur

We've had AHJ ask for things after the permit docs are approved all the time... but always during construction. We would request in writing what code and or zoning regulation requires the radon dealie and, if they can't produce it in black and white, then issue a letter stating that since it is not a requirement, it was not installed.


Agreed it's crazy for a space with 6 regularly-used pull through bays.

But radon levels change, so in a less obviously constantly ventilated situation it's not so extremely crazy to design for possibility.  Ground saturation or freezing affects test results. So does wind.  On a longer-term basis settling of the building can change radon levels, as can surrounding construction, shifting ground conditions, changes in water levels and drainage.

The rock types here make my location prone to radon, so it's pretty normal for the AHJ to require it, though seems less reasonable if you're not in a place with as high a likelihood of excessive levels.

Dec 12, 18 4:56 pm

I live on silty clay, way more concerned about heaving foundations than radon


It's a hell of a lot easier to put it in now than it will be later...

Dec 12, 18 5:08 pm

But that cost should be up to the client to decide. Pay a little now or a lot later. I would roll the dice on my 6 bay shop

The local Authoraties are asking for it, I would consider how much time and money it would take to appeal this and possibly win them over and consider the lost time for the client's building and then compare that to the cost of complying with the radon mitigation. If you have a lot of potential expense to put this in then it might be worth fighting but if it is a small cost overall and delaying delivery of the building to appeal an AHJ's decision will likely (even if you win) cost the client more than the install of the radon mitigation system then it might be a good idea to put it in and move on. Fighting this might not ad value to the project, but if this is the type of project that will be repeated over and over again like a chain of stores then it might be worth it for the future savings of other projects.


We've been doing it for all projects for about 10 years. 

Dec 12, 18 6:04 pm

isnt this just a perforated pvc relief pipe and heavy duty vapor barrier under the slab on grade? do they have more onerous requirements?

Dec 12, 18 10:27 pm

But if the slab on grade is already poured ...

Then I hope the architect in question has good insurance as this should have been a know requirement and the architect will be on the hook.


I have a standata that states its up to the professional and the plans were already approved by the AHJ.

Non Sequitur

Are you not the professional?


yes that is my whole point

Ask the AHJ to look at the stamp on the drawings. Then ask them if it says their name. Then ask them who the professional is again.


End of the day they either issue you an occupancy permit or they don't. If they don't, lawyers get involved.

wurdan freo

thank god for inspectors. They really save the day.

Dec 14, 18 12:20 am

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