Sill plate vs top plate size

[mnpeterg]

Building a 30x16 shed.

2x6 walls

Turned down footers in my city are a good provided they are 12’’x12’’ with rebar.

I’m using standard 8x8x16 cmu’s as the curb. Than putting the sill on top of the blocks.

Here’s the question that I can’t get my head wrapped around. Can I use a 2x8 sill plate but have the top plates be 2x6?

 

[billconner]

Yes. just what I did for, I'd guess, similar reasons. In my case, using rough cut, 8" cmu is completely covered.

 

[mnpeterg]

Did you attach the 2x6 ‘s in the middle of rhe 2x8 sill plate or fully aligned with one side? I suppose the benefit of one side would be for the exterior sheathing to be flush.??

Yes. just what I did for, I'd guess, similar reasons. In my case, using rough cut, 8" cmu is completely covered.

 

[ddurrett896]

top plate matches the studs, bottom plate can be same as top or larger.

stud and top plate should be flush with outside edge of bottom plate.

 

[mnpeterg]

top plate matches the studs, bottom plate can be same as top or larger.

stud and top plate should be flush with outside edge of bottom plate.

Thanks ddurrett896, I appreciate your help. confirm 'outside of bottom plate’ is exterior side of bottom plate. thanks

 

[billconner]

Did you attach the 2x6 ‘s in the middle of rhe 2x8 sill plate or fully aligned with one side? I suppose the benefit of one side would be for the exterior sheathing to be flush.??

I flushed outside of stud and plate and set both about 3/4" back from face of CMU so the rough sawn sheathing was proud of CMU by an 1/8"+. The board and batten siding then overhangs by an inch. Yes, diagonal wood board sheathing (for lateral bracing) on way 24" on center and classic board and batten siding over sheathing.

 

[rayra]

Building a 30x16 shed.

2x6 walls

Turned down footers in my city are a good provided they are 12’’x12’’ with rebar.

I’m using standard 8x8x16 cmu’s as the curb. Than putting the sill on top of the blocks.

Here’s the question that I can’t get my head wrapped around. Can I use a 2x8 sill plate but have the top plates be 2x6?

Heavens! what will the neighbors think.

Of course you can, but why? Just trying to cap the block?, btw, that block ought to be filled / grouted. How would you do that after you've capped it with a 2x8? Doing it before? Or not at all?

The bigger hassle is building the wall on the floor and tilting it up. How do you build that assembly flat on the floor when the lower sill is 2" wider? You'd have to shim the entire thing (except your 2x8 bottom) up off the floor by 2" while you build it. And that isn't as convenient as it sounds.

If you are going to rip a bunch of boards to 2" to serve as shim, you might as well use a 2x6 for the bottom and tack some ~2-1/2" wide boards to the inboard edge of a 2x6 bottom plate to cap off your block. Either way you'd be ripping some studs.

Not even expecting you could just **** a 2x3 against the 2x6 to span the width, as there are lots of variations in CMUs, rarely are they a full 8"W. And now you'd have your lumber cap overhanging inboard a small amount.

 

[Mandres]

I agree, it doesn't make much sense to me to use a 2x8 sill. Wouldn't that leave an inch and a half of exposed wood protruding under the baseboards?

 

[billconner]

I agree, it doesn't make much sense to me to use a 2x8 sill. Wouldn't that leave an inch and a half of exposed wood protruding under the baseboards?

It's on top of a block wall.

I built my walls in place. No big deal. Stem wall was stepped since it was set into a slope. And I did grout every 6 or 7th cell as well as entire top course. Besides, no interior wall covering so looks better than tacking on a strip.

 

[andyvh1959]

For my 24x28 shop build, I had two rows of 8" block laid after the slab was done. The anchor rods came up through the block from the slab, the rods were set in the slab as it was poured. I built 2x6 walls with 2x6 sill and top plate, just filled the block with insulation/foam. The walls were flush to the outsdie of the block, and I covered the inside with 7/16" OSB. It only left about a 1/2" gap at most over the block which could easily be covered with a 1x4 "baseboard" to finish the wall. Easy to build the walls on the slab since everything was the same thickness, no spacers or shims to frame up the walls on the floor before we tipped them up onto the block.

 

[Skiff Builder]

Not really hard to frame on floor using different width plates.
Layout, nail studs to 2x6 top plate.
Move to the 2x8 end.
Lift each stud 1-3/4" with your support side hand (flush to top of 2x8), shoot 3 16d in through bottom plate, as you nail them off.
Could also use 1 short block of 1-3/4" x12" scrap as a shim-kick along floor as you go to nail each stud.

 

[Monza Harry]

Is thre a code reason for not being able to use a 6" CMU for the top course (It is already there is an even better reason)? You may have to fill the top course of 8" CMU's before the 6" caps are laid, but this (6"CMU's) would create an ~even surface inside and out. Harry

 

[billconner]

As I read the IRC, only solid (not grouted) 6" blocks can be used. I tried to figure out a way for the obvious reason of aligning with 2x6 walls, but couldn't.

You can always ask if your building department will accept them.

I'll look for the section and post it.

 

[Monza Harry]

Bill solid only? I'm wondering if you could just fill the hollow 2 core CMU's. Harry
Added thought, could a curb [@ 6" wide] be poured on top of the 8" CMU's

 

[Hakeem]

Not really hard to frame on floor using different width plates.
Layout, nail studs to 2x6 top plate.
Move to the 2x8 end.
Lift each stud 1-3/4" with your support side hand (flush to top of 2x8), shoot 3 16d in through bottom plate, as you nail them off.
Could also use 1 short block of 1-3/4" x12" scrap as a shim-kick along floor as you go to nail each stud.

Right, although I would just prop the wall studs on a 2x so you’re not lifting countless 2x6s.

I just checked my lumberyard, 2x8x12 #2 spf is only 20-25% more than 2x6x12 of same grade. Do 19.6” OC or even 24” OC with the supersized wall studs and you’re coming out ahead costwise.

 

[billconner]

Bill solid only? I'm wondering if you could just fill the hollow 2 core CMU's. Harry
Added thought, could a curb [@ 6" wide] be poured on top of the 8" CMU's

Well I reread it and am less sure. The chart is very specific about the distinction between solid and grouted, but perhaps grouted can be used in place of solid and for taller/more unbalanced fill walks, not the other way.

Sorry, just not sure.

It's TABLE R404.1.1(1) PLAIN MASONRY FOUNDATION WALLS in the IRC. I think you can find it online for free. Try up.codes or just Google that table

 

[billconner]

I just checked my lumberyard, 2x8x12 #2 spf is only 20-25% more than 2x6x12 of same grade. Do 19.6” OC or even 24” OC with the supersized wall studs and you’re coming out ahead costwise.

24" o c. and use 22" windows so no headers or jacks.

 

[Skiff Builder]

Not really hard to frame on floor using different width plates.
Layout, nail studs to 2x6 top plate.
Move to the 2x8 end.
Lift each stud 1-3/4" with your support side hand (flush to top of 2x8), shoot 3 16d in through bottom plate, as you nail them off.
Could also use 1 short block of 1-3/4" x12" scrap as a shim-kick along floor as you go to nail each stud.

Right, although I would just prop the wall studs on a 2x so you’re not lifting countless 2x6s.

2x6 (5.5") 2x8 (7.25") Difference (1.75") Prop them on a 2x (1.5") and your still lifting each stud a bit. Part of building is moving and lifting lumber- can't get away from it. Or you could rip down a 2x4 to 1-3/4" ( like RAYRA said) and do what you suggest. Either way ,in the end, any of the methods are about the same time spent.

 

[KenC]

Well I reread it and am less sure. The chart is very specific about the distinction between solid and grouted, but perhaps grouted can be used in place of solid and for taller/more unbalanced fill walks, not the other way.

Sorry, just not sure.

It's TABLE R404.1.1(1) PLAIN MASONRY FOUNDATION WALLS in the IRC. I think you can find it online for free. Try up.codes or just Google that table

I don't think those tables apply to his circumstance. Here is the prelude to them from the IRC.

R404.1.1Design required.​

Concrete or masonry foundation walls shall be designed in accordance with accepted engineering practice where either of the following conditions exists:

1. 1.Walls are subject to hydrostatic pressure from ground water.
2. 2.Walls supporting more than 48 inches (1219 mm) of unbalanced backfill that do not have permanent lateral support at the top or bottom

Neither condition seems to exist for his build.

 

[ddurrett896]

I’m using standard 8x8x16 cmu’s as the curb. Than putting the sill on top of the blocks.

How many courses? Highly recommend filling all cells with mortar (cheap) and #4 rebar tied into the footer. I would....

- Pour footer
- Set block
- Drill into footer every 4' and epoxy #4 rebar thru all courses
- Pour slab - order extra concrete and fill all block cells, making a bond beam.
- Set galvanized anchor bolts in the wet mortar every 4' to bolt bottom plate to block. Be sure you have your layout so once placed, there is a bolt within 1' of the bottom plate ends.

 

[billconner]

How many courses? Highly recommend filling all cells with mortar (cheap) and #4 rebar tied into the footer. I would....

- Pour footer
- Set block
- Drill into footer every 4' and epoxy #4 rebar thru all courses
- Pour slab - order extra concrete and fill all block cells, making a bond beam.
- Set galvanized anchor bolts in the wet mortar every 4' to bolt bottom plate to block. Be sure you have your layout so once placed, there is a bolt within 1' of the bottom plate ends.

Basically what I did but only filled cores with rebar, and all of top course. Varied from 3 to 7 courses.