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Building backyard shed on slab-on-grade: question about mud sill on foundation

Building backyard shed on slab-on-grade: question about mud sill on foundation


  #1  
Old 06-22-24, 11:38 AM
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Building backyard shed on slab-on-grade: question about mud sill on foundation

Hi,

First post here ever. Thanks for reading it.

I am planning a backyard shed with a slab on grade foundation. Location is the Bay Area in California. Shed size is about 12í x 10í.

Iím planning to use a PT 2x4 mud sill. Iíll be drilling holes in the concrete to install anchors to fasten the mud sill, roughly at intervals as shown by the red dots in the attached photo. Is there a particular type of flashing and adhesive I should use between the mud sill and the concrete slab for moisture and to keep out pests? If so, would you share what product I should use?

I appreciate any battle-hardened advice anyway can share for this project. As you can see in the photo, itís stalled for a while. I poured this foundation about seven years ago. lol



Thanks,
Ryan
 
  #2  
Old 06-22-24, 11:45 AM
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There are a number of products available for sill seals. Stop by a big box store or a local building supply and ask for sill seals. You can also order from Amazon.
 
Rpguitar1 voted this post useful.
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Old 06-22-24, 12:12 PM
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Do yourself a favor and lay a row of concrete blocks around the perimeter first. Grout any hollow blocks within 6 - 12" of the outside corners and doorways then every 6 feet on center... then drill, clean blow dust out and epoxy 1/2" x 12" all thread in for your bottom plate to bolt to... it should stick up 2 1/2" above your block. Then put down sill sealer and build your wall on top of that.

It gets your siding 6"+ above grade and it will last longer and be less of a maintenance issue down the road.
 
  #4  
Old 06-22-24, 12:40 PM
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Concrete blocks, as XSleeper suggested are a good idea, but adds a lot of work. I would use a doubled-up mudsill and construction adhesive between the mudsill and the concrete. The doubled-up mudsill would allow you to keep the siding away from the ground a little more than a single plate.
 
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Old 06-22-24, 06:58 PM
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XSleeper , thank you for the response. By concrete blocks, do you mean hollow ones like this:

https://www.homedepot.com/p/6-in-x-8...0100/100322580

Or solid ones like this:

https://www.homedepot.com/p/4-in-x-8...8621/100350217

Or either one, doesn't matter?

Also, I understand what you mean about using the all thread for fastening the mud sill to the foundation, but would I also use some all thread to fasten the bricks to the foundation, too?

Whittsend , thank you also for your suggestion. Using the doubled-up PT mud sill route, would the mud sill be visible from the outside of the structure once the siding is installed? Meaning, before I asked for advice, I would have thought the siding would extend about 3/4" down beyond the mud sill overlapping a portion of the foundation. What do you think?

Wayne Mitchell , thanks for telling me about sill seal. I'll definitely get some of this.

Thanks again, guys.

-Ryan
 
  #6  
Old 06-22-24, 07:24 PM
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Yes, hollow ones so that you can drill into your existing pad (you have to plan exactly where those bolts should fall), epoxy the 12" long all thread into the holes you drill in the pad, (clean with a pipe brush and blow clean before shooting the epoxy in the hole, then insert the all thread) then lay the blocks into a mortar bed (mortar mix) and position them over the all thread and once the blocks are all down, grout the blocks full that have the all thread in them. Then you put your sill sealer on top of the block, (push it down over the all thread bolts to keep it from blowing away in the wind), drill holes in your plate to go over the bolts, and put your washers and nuts on. Alternatively you can staple the sill sealer to the bottom of your sill plates before you install them.

The all thread is really just connecting the sill to the pad so that the shed doesn't blow away. Most building codes require buildings to be anchored. The mortar is like the glue for the concrete blocks. It should be mixed stiff enough to remain about 3/8"- 1/2" thick when you set the block on it, tap it and level it. Mortar goes under the blocks and between them... whatever squishes out after the joint is 3/8" - 1/2" wide is scraped off with a trowel and put on the next block... then joints are typically smoothed with a jointer tool.

It's not rocket science but yeah it takes more time to do it right.
 

Last edited by XSleeper; 06-22-24 at 07:34 PM.
  #7  
Old 06-22-24, 08:33 PM
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I would try and keep the siding a couple of inches off the ground. If the siding gets too close to the ground you're going to end up with rotting siding if you're using wood.
 
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Old 07-01-24, 11:13 AM
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Thanks for the help, everyone!
 
 

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