Hardi Plank over Cedar?

Well it could be done, but I wouldn't recommend it. You don't say what kind of cedar siding you are using..lap cedar is assume? Fiber cement is quite heavy, and your firring strips will have to be attached with fasteners that penetrate the framing. No small job. Second, how are you going to detail the new siding around the windows and doors so they both look decent and remain water tight? And will the furring strips lay flat? So yes, I think it could be done, but would it be much easier than just ripping the old cedar off? Plus I think the insulation value of an airspace and some cedar siding is quite minimal.

He's looking for less trouble. Less trouble would be to scrape the cedar boards and repaint the cedar with a good quality paint. I have Hardi board on my shop and it still needs to be painted every few years. He's not gaining anything unless the cedar is failing but he didn't say that.

No - the cedar is not failing, but in my experience, scraping off the old paint bubbles leaves bare blotches that must then be sanded flat inorder to blend in with the rest of the board. I could put on a pre painted board faster - I think. This is beveled siding, with 6" exposure.

Thanks for the heads up on the firing strips. Yes that would be a lot of weight!

RO

If you're looking for something maintenance free then you should consider vinyl siding. It will go right over the cedar and you can install it in a day. HardiBoard or HardiPlanks will still need to be painted, however vinyl siding only needs to be pressure washed maybe once a year.