Installing a Subfloor Over Decking

It’s not always necessary to remove the decking before installing a subfloor for a four-season addition built over an existing raised deck framed with PT lumber, but it might be a good idea. Much depends on whether or not the deck footings, framing, and house connections are adequate for the anticipated loads, and if the existing decking is sound and reasonably flat. And even then, there may be advantages to doing so anyway, such as avoiding squeaky or bumpy floor sheathing. But if you’re going to do it anyway, the APA’s Bryan Readling explains exactly how to do it right in this classic JLC Q&A.