Re: Is pre drilling cement board siding required
Since you're installing lag screws, you really want the screws to be biting into the wood behind the siding, since the siding itself isn't going to have the structural integrity to hold any weight by itself. So yes, you should predrill through the siding. The pilot hole through the siding should be equal to the outer diameter of the screw threads; the pilot hole in the wood behind should be equal to the inner diameter of the threads (or slightly smaller). Failing to at least predrill the siding could cause a blowout of the fiber cement product.
The "Senior Member" designation under my name doesn't mean I know a lot, it just means I talk a lot.I've been a DIYer since I was 12 (thanks, Dad!). I have read several books on various home improvement topics. I do not have any current code books I can refer to. I was an apprentice plumber for two years.