# Should the mudsill be set back the distance of the sheathing on a slab foundation?



## moorehead (Nov 11, 2015)

Just a note, I wrote distance in the title but meant thickness.

I live in Oklahoma and plan to build a small livable structure next year. I'm in the planning and researching stages. I'm currently looking for the codes regarding my question, but I'd also like to hear what is common plus the pros and cons.

I ask that you please don't be rude. I am in the very early stages of researching and learning these things. Please don't comment, "None of this matters. Go look at the codes!" I'm simply asking what is common and what are the pros and cons. I do appreciate everyone reading very much. And look forward to all replies.

When it comes to a slab foundation, what are the pros and cons of setting the sill plate back the thickness of the sheathing in order to allow the face of the sheathing to be flush with the foundation face? Then when you attach the siding you can set it a bit below the sheathing to overlap the foundation face and the siding creates a drip edge?

What are the pros and cons of setting the sill plate flush with the face of the slab and then having the sheathing overhang the slab face?

Which of the two are more common?

Just using my common sense I'd say that setting the sill plate back and not letting the sheathing overhang would be the better option. Because when you apply the siding you are basically hiding the wood completely. Especially with the membrane in there. Plus everything lines up.

Thank you again for reading.

Edited for spelling


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## Ron6519 (Mar 28, 2007)

How far off the ground will the plywood sheathing be? Setting the plywood in a pocket might cause water intrusion to rot the wood.


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## moorehead (Nov 11, 2015)

Ron6519 said:


> How far off the ground will the plywood sheathing be? Setting the plywood in a pocket might cause water intrusion to rot the wood.


I'm having a hell of a time finding the codes specific to my area regarding what the minimum height is above grade. I'm pretty sure it's between 6-8 inches. Thanks for bringing this up. I think what'll I'll do is plan from the bottom up and you gave a good idea of things I need to look for.

So let's say 8 inches above grade. I'm guessing by pocket you're refering to the first option with the pocket being the space in front of the sill plate.


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## ront02769 (Nov 28, 2008)

Not a professional...but even in a house with foundation and baSement, I am setting tine outer end of the PT mud sill maybe a quarter inch overhanging the foundation OR the foundation insulation. (Where I am, you need two inches of foam insulation on the outside of the foundation so I will run it over two and a quarter inches.) Then everything that drips down drips down outside stuff. Is it right? Don't care. Works. Ront


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## joecaption (Nov 30, 2011)

Bottom plate needs to be even with the outside of the slab.
Sheathing needs to run past the slab, not sit on top of it.
1/4" would not be enough, more like a minimum of 1/2".


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## moorehead (Nov 11, 2015)

joecaption said:


> Bottom plate needs to be even with the outside of the slab.
> Sheathing needs to run past the slab, not sit on top of it.
> 1/4" would not be enough, more like a minimum of 1/2".



Joe, could you please elaborate a bit and also answer why?


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## woodworkbykirk (Sep 25, 2011)

what he's saying is that your mudsil should be even with edge of the slab so that when you install your sheathing it can run down past the edge of the slab to create a overlap. specifically so that when water runs down the wall it wont run directly down onto the edge of the slab which is what will happen the way you plan to do it,, which in turn means a leak and then rot


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## gregzoll (Dec 25, 2006)

If you are in Oklahoma. What are you doing for a Tornado shelter? Also keep in mind that you have to use straps to hold the trusses on, along with keeping the walls and trusses tied together, including the foundation.


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## TheEplumber (Jul 20, 2010)

woodworkbykirk said:


> what he's saying is that your mudsil should be even with edge of the slab so that when you install your sheathing it can run down past the edge of the slab to create a overlap. specifically so that when water runs down the wall it wont run directly down onto the edge of the slab which is what will happen the way you plan to do it,, which in turn means a leak and then rot


Isn't that what the siding is for- to shed water? If the siding is doing it's job then water won't reach the sill or sub siding. Asking for clarification.


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## ront02769 (Nov 28, 2008)

Read to my post above as to why it may need to overhand. And not to contradict others but if the edge of the plate is dead even with the foundation, then it is likely that the plywood when installed will hit said foundation....and end rotting out. Ron


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## MTN REMODEL LLC (Sep 11, 2010)

ront02769 said:


> Not a professional...but even in a house with foundation and baSement, I am setting tine outer end of the PT mud sill maybe a quarter inch overhanging the foundation OR the foundation insulation. (Where I am, you need two inches of foam insulation on the outside of the foundation so I will run it over two and a quarter inches.) Then everything that drips down drips down outside stuff. Is it right? Don't care. Works. Ront





ront02769 said:


> Read to my post above as to why it may need to overhand. And not to contradict others but if the edge of the plate is dead even with the foundation, then it is likely that the plywood when installed will hit said foundation....and end rotting out. Ron


Ront.... Are you saying your mud sill is overhanging the concrete stem wall by 2 1/2 inches.... because you run your foundation insulation up to butt under your mudsill....????? 

Hope you are in 2x6 material... even then... almost have your mudsill and outside bearing framing is almost 50% unsupported...??

Gues I don't understand


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## moorehead (Nov 11, 2015)

woodworkbykirk said:


> what he's saying is that your mudsil should be even with edge of the slab so that when you install your sheathing it can run down past the edge of the slab to create a overlap. specifically so that when water runs down the wall it wont run directly down onto the edge of the slab which is what will happen the way you plan to do it,, which in turn means a leak and then rot


I don't have a plan on how I'm going to do it. Which is the point of asking pros and cons here.

If the sheathing sits on on the foundation wouldn't the siding overlapping prevent the running down onto the foundation regardless? I'm basically asking, what specifically are the pros to having the sheathing over hang? Just because of the added protection it would provide?

Thinking about it though, by allowing the sheathing to overhang that gives the siding something be actually be fixed to and I would have the thickness of the sheathing and siding there to protect from water. So I think I see where you're coming from. Am I way off?

On a raised foundation with wooden floor joists and plywood on top do they have the sheathing overhang?

Why is it a bad idea to have the sheathing sit on the foundation? Legitimately asking all of these things in order to understand. Thanks everyone.


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## gregzoll (Dec 25, 2006)

You do realize that you can do a search for Siding installation, or just take a walk around the neighborhood and see.

All of the houses around me that have 60+ year old Aluminum siding. They have at least two sections below the Rim Band, which is about 2 feet above ground. When I had my house done over the Summer, because of the siding got torn off by winds. They went down to about 4" from the ground with the new siding, with Pressure Treated Plywood attached to the Block Foundation, so that the new siding will attach.

If you look at the picture of what my house used to look like. Where the Front door is. That is actually the Rim Band for the Basement. As you can see, they went two sections below the Rim for the Siding, which actually looked a little retarded, because one section always blocked the Basement Windows.


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## moorehead (Nov 11, 2015)

gregzoll said:


> You do realize that you can do a search for Siding installation, or just take a walk around the neighborhood and see.


Nah. I don't live in a neighborhood. Plus only slab foundation in my direct area is a McDonalds. I did walk over when it was built and the sheathing appeared to be on the slab. But I personally don't think it's a good idea to let one example become a baseline. Plus I like reading other's insight, thought process, advice, etc on this forum.

Yes I've search siding installation but nothing really talked about the mudsill,slab foundations, and sheathing. Just how to affix and lay the siding.

I'll look again later today. Thanks for the example!


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## gregzoll (Dec 25, 2006)

No siding you will find, is going to be all the way down to the ground. The lowest that it will go, is where the top of the slab is, so that anything covering the walls, will not be affected.

In your case, you are in Tornado alley, so that means you have to put extra cost into making sure that the structure meets current standards for a minimum of EF-1 in most areas.

Moore, OK and Joplin, MO actually have raised the standards to almost having the structures meet the same criteria that homes in areas that can be affected by Hurricanes.

OKC went as far as requiring that structures have at least 50% brick and other changes, so that there are less debris. Also the builders that rebuilt the homes went further then the minimum of just sheathing on the corners as the code states. They are placing 3/4" max on the whole structure, to make sure that it lessens the chance of the structure collapsing and becoming a flying hazard.

You need to first go find out your codes, what your area requires for what you can use on the outside. That means you are probably right now about five steps ahead of yourself.

I would be worrying more about the actual structure shell itself and the codes that require you to make sure that it does not fly away. That means also that you may not be allowed to use Vinyl Siding. You may be required to use Brick or Stone.

Go do your homework with the local Building codes, go look at other structures that are either in construction in neighborhoods, or have been fixed for the newer standards to make sure that they do not become a debris path.

As I stated for mine and as I look over at the new building for the sub shop across the street from me. The lowest that they will go with any siding, is the top of the slab, or below the Rim Band. Except in my case, we went 4" from the ground, which is typical if I had a slab home.


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## hand drive (Apr 21, 2012)

moorehead said:


> Nah. I don't live in a neighborhood. Plus only slab foundation in my direct area is a McDonalds. I did walk over when it was built and the sheathing appeared to be on the slab. But I personally don't think it's a good idea to let one example become a baseline. Plus I like reading other's insight, thought process, advice, etc on this forum.
> 
> Yes I've search siding installation but nothing really talked about the mudsill,slab foundations, and sheathing. Just how to affix and lay the siding.
> 
> I'll look again later today. Thanks for the example!


personally here in the Raleigh/Durham area when using hardie siding I set the mud/sill back a 1/2" from the foundation and hold the sheathing up 1/4" ( carpenters pencil thickness) off of foundation. then the hardie and corner boards go down 1" onto foundation. I have never seen a straight foundation so the back underside of the siding will need to be caulked against the foundation to fill the voids to keep critters and the elements out.

if you run the sheathing out and down onto foundation the sheathing will rot out there from the concrete and wood touching. if you do run it down onto the foundation use sticky membrane to somehow wrap the under exposed side of the exposed sheathing or give an extra 1/4" out so the sheathing actually floats without touching concrete.


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## ddawg16 (Aug 15, 2011)

This is the best picture I could find on short notice. My bottom plate sits in about 1/2". In my case, I have stucco....outside sheathing gets covered with building paper...at the bottom is a weep edge that extends below the edge of the bottom plate.

I actually have about 1/8" of space between my OSB and the slab. I painted all the edges and before the sheathing went up, I can a bead of silicone to prevent water and bugs getting in.


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## moorehead (Nov 11, 2015)

Thank you so much hard_drive and ddawg!

@hard_drive your description is the one I thought would be most common when starting this thread.
@ddawg16 thanks a lot for that picture. Painting the edges was a nice touch.

The reason I was wondering about setting the mudsill back has partly to do with wanting to do partial brick on my structure. I just assumed floating the sheathing above the slab and sealing it with silicone made the modst sense because it gives you a flush surface to lay brick against. Plus, it allows you to hide the wood completely. But I'm sure there are cons as well.

Which leads to a question. Other uers are saying to let the sheathing be outside and overhang a the slab face a bit. If you were to lay brick wouldn't there be a void between the brick and the slab under the sheathing overhang? What would you fill that void with?

@gregzoll I'm more exploring different avenues of options. I haven
t made any set plans. Plus I'm just really curious about this topic in general. I plan to research codes pretty heavily this weekend. As far as the shell goes, that information is easily available. This topic was just a bit hard to research so I asked.


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## jomama45 (Nov 13, 2008)

There's no right or wrong answer really, just personal preference for the framer. We pour slabs all the time, and I generally go over this with the framer before we set forms. Probably a 50/50 split here in preference.

As for the brick, you'r going to need an air space behind it anyways, if you're doing full veneer. Generally speaking, leaving the framing flush with the higher part fo the slab will let you utilize the entire brick ledge........


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## moorehead (Nov 11, 2015)

jomama45 said:


> There's no right or wrong answer really, just personal preference for the framer. We pour slabs all the time, and I generally go over this with the framer before we set forms. Probably a 50/50 split here in preference.
> 
> As for the brick, you'r going to need an air space behind it anyways, if you're doing full veneer. Generally speaking, leaving the framing flush with the higher part fo the slab will let you utilize the entire brick ledge........


Makes sense.


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## woodworkbykirk (Sep 25, 2011)

TheEplumber said:


> Isn't that what the siding is for- to shed water? If the siding is doing it's job then water won't reach the sill or sub siding. Asking for clarification.



yes and no. siding is there to shed water however its never 100% waterproof.. the house should be waterproof before teh siding even goes on the wall.. you achieve that by properly overlapping the sheathing the foundation. and then the house wrap goes on . its in the code book clear as day


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## TheEplumber (Jul 20, 2010)

Not that I don't believe you but can I have the reference?
I don't see it done like that around my parts


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## hand drive (Apr 21, 2012)

moorehead said:


> Thank you so much hard_drive and ddawg!
> 
> @*hard_drive* your description is the one I thought would be most common when starting this thread.
> @*ddawg16* thanks a lot for that picture. Painting the edges was a nice touch.
> ...



your mason can tell you what he needs to get the brick up on the wall and how the sheathing should be. my guess, he wants the sheathing flush with the foundation and his 1/2" space behind the brick with clips will work...


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