Subfloor Calculation for Dummies - The Freelance Files MMXCVIII

Subfloor construction

For some reason, some of the most straightforward questions addressed by the "contributors" at the former eHow.com could bring out the... abject stupidity inherent in those freelancers' ignorance of their topic. We ran across one of those just today; a repeat DotD by the name of David Robinson (based on his bio, he was not the former San Antonio Spurs center). Robinson clearly demonstrated his ignorance of building construction in the Hunker.com post, "How to Calculate How Much Plywood You Need for a Floor."

Given Robinson's first step, it's readily apparent that he thought the OQ wanted to lay a plywood floor. To that end, David performed heavy research on hardwood flooring (which he apparently did not realize isn't the same thing as plywood), racking up five or six references in the eHow original. What he does not seem to have understood is that, except for sheds, attics, and other utilitarian spaces; plywood only serves as the subflooring in ordinary construction. That's why his first step,

"Determine the edges of the area to be floored with plywood. Consider whether the wood will cover the visible part of the existing floor space or whether it needs to continue under skirting boards to allow for shrinkage and expansion..."

...seemed so bizarre. Does Robinson really think that someone laying a floor does so with the baseboard molding ("skirting" in David's native UK) in place? Hell to the no!

He compounded that utter stupidity in a later step, in which he discussed fitting the plywood under any baseboard molding:

"For example, if a room is 10 feet wide, and the plywood needs to extend 2 inches under the skirting board on each side of the room, adjust the width to become 10 feet 4 inches."

Wait, what? two inches past the leading edge of the baseboard? Either David's been working with some ridiculously thick molding or he isn't aware that there's framing behind that drywall. And we wish he understood that you don't finish a wall with sheetrock and molding before you lay the subfloor; the baseboard goes on last (except for paint and/or paper).

Robinson followed that with boilerplate about calculating areas – break the floor plan into rectangles, etc. – before calculating the number of sheets of plywood you will need. Dave also explained that,

"Plywood is sold in whole sheets -- you can't buy part of a sheet..."

...suggesting that he hasn't been in a BigBox hardware store that sells so-called "project panels," but we'll give him a pass on that.

We thought that Robinson had missed the chance to tell people to order an additional 10% for waste, but that was actually included in a "tip" in his original. So not only is Robinson today's Dumbass of the Day for the crap about "extend 2 inches under the skirting board" but the idjit who ported the post from eHow to Hunker also gets a nod from the nominating committee. Everyone concerned, however, gets an award for not knowing that non-load bearing interior walls are set on top of the subfloor (see image above)...

DDIY - FLOORS