How do you make flush cuts to a precise depth?

Question

I'm renovating a small shed that was built with 2x4 wall studs on top of 2x6 bottom plates, for some reason. I'm realizing that this will create a problem once I get to the drywall and flooring stages, as I will need to either raise the subfloor, thicken the walls, or cut down the bottom plates to match the 2x4 wall thickness. Raising the floor or thickening the walls present substantial complications and additional costs, so I feel like cutting down the bottom plates to 2x4 thickness to match the existing wall makes the most sense. However this would require making flush cuts at the exact height of the bottom plates (1.5") to avoid damaging the subfloor and floor joists below.

How do I make flush cuts to a fairly precise 1.5" depth as required here?

A circular saw wouldn't do because I can't make a flush cut with it, and a sawzall with a flexible blade would damage the subfloor and joists below the top plate. Could an angle grinder work with some kind of flush cutting blade? Would one of those fancy Japanese pull-saws work?

Answer 1

Since you're insulating and dry walling this "shed", you may want to treat it as an additional room, where extra insulation would go a long way toward your comfort.

Although it's possible to rip 1.5" off the edge of the 2x6 with an oscillating saw, you're likely to burn through several blades, and possibly a saw or 2 doing it. It'll be much easier to add 2x2 furring onto your 2x4 studs to make up the thickness. If you're insulating and dry walling, this would also let you add more insulation for a more comfortable room with only minimal cost and labor.

For more strength, in addition to insulation, if you have 2x6 top plates also, you could sister in 2x6 studs or add offset 2x4 studs between the existing ones for a double- stud wall.

Answer 2

It is an investment, but there are flush cutting circular saws out there, also called a jamb saw. Or perhaps a rental??

A lot of flooring people use them for cutting door jambs off to get the flooring under the bottoms

Answer 3

If you don't have a lot I would use a normal hand wood saw. You can use you circular saw to do some of the work in between joist. An oscillating tool with a blade for rough wood will work as well.

If you are careful with a long blade on the reciprocating saw, you won't damage much of the subfloor. Go slow, steady, at a consistent angle, in multiple passes

Answer 4

I really think you are making this way too hard...

A thing to think about since this is a shed is using the 2x6 as a kickplate. You don't want it sticking out 2" though. But given you are putting up drywall at 1/2"...

You can:

1. Install drywall plus trim to meet flush with 2x6 (this would in effect make your trim higher).

2. Install drywall flush with 2x6 and put trim on top of that. Probably the cleaner look.

This means that you can either leave a half inch or a full inch sticking out.

If you cannot reach do this with a circular saw (I would go 95% and chisel out) then I would use an electric planer. Mine does 1/16" at a time max so at most that is 24 passes which would take about 15 mins (note not all planers can cut flush with ground). Obviously circular saw way faster but a planer here is easy too.

If these don't work I would look for a plunge cut saw. With a reciprocating saw would being doable but a mess and an oscillating saw might take a day.

Answer 5

A grinder with the right blade should do it, plus it’s something that most people already own.

Answer 6

This is not a pleasant job to have to do for obvious reasons. I'd get rowdy with it and fix the drywall backing later. You'll spend a lot of time trying to cut it cleanly otherwise.

1. Set your circular saw to depth (about 1-5/8") and cut between each stud, back 1/2" or so from flush. If the grain in your plates is very straight, 1/4" might do.
2. Using a flat bar or framing hammer, pry the front portion of the stud outward. It'll split along the grain. The split won't be perfectly straight, but your goal here is just to remove the offending wood. Encourage it with a chisel if needed.
3. Use a chisel or reciprocating saw to remove any wood protruding beyond the face of the studs due to curving grain.
4. Lay in blocks above the mangled plate in each stud bay to act as drywall backing.

Answer 7

I happen to love my oscillating saw that may be useful for cuts of this type.

They are pretty lightweight but you will still need to practice some for long cuts.