Shims on Piers

[Mike Hunger]

I found this during an inspection last week. Another inspector told me that the wood "shim" is unacceptable. It appears that the builder designed the system to allow the floor joists to sit on dimensional lumber that is the same size as the sill plate. I understand that it can compress... but so can a sill plate. What think ye??

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[Richard Stanley]

What would "another inspector" call it? Perhaps elevation differential modification support??? I'd call it a shim.

[John Arnold]

What would "another inspector" call it? Perhaps elevation differential modification support??? I'd call it a shim.

Did you think he said the "word" shim is unacceptable?

[Michael Thomas]

Perhaps confusing the concepts of "shim" (constant thickness supporting spacer) and "tapered shim" (adjustable thickness supporting spacer)?

But in any case "I say it's a shim"...:

[Mike Hunger]

Yep... it's a shim. My question is: Is this acceptable building practice by the latest code? I have been told that wood shims are unacceptable between the top of a pier and a floor joist. I see plenty of this in my area - the Triad area of NC. Trying to get some feedback from other areas.
Thanks.

[Markus Keller]

I don't define it as a shim. I think that over simplifies it in this case. It really is a 'spacer' to make up for the lack of height in the column. Clearly the bricky and carpenter weren't talking to each other well enough.
- I prefer to see hardwood spacers with a piece of tyvek, rubber roofing, etc separating the hardwood and masonry. I can accept pine/treated if it is full size and not splitting
- I would call for the 'spacer' to be the full size of the column to distribute the load
- Metal spacers work well too, 1/4" plate is easy to get
Shims - change in thickness
Spacers- stay constant in thickness
My thoughts on it.

[Jerry Peck]

1) It's a "shim".

2) It's allowed provided: a) the species is sufficient to support the load; b) the size is sufficient to provide at least minimum bearing area; c) the grain runs perpendicular to the girder and not parallel with the girder (common sense so the weight of the girder does not split it); d) that the shim is somehow secured in place so it cannot move out of place on its own (this may not be required in some areas, but it is still a 'smart and common sense' think to do).

[Michael Thomas]

Jerry,

Which of those are are those code requirements and which are "best practice", for example where would I find a table of the allowable compressive loads for various species of wood?

[Ron Bibler]

Say thats a nice sub-structure.

It would be nice if they all look like that.

Best

Ron

[Richard Pultar]

I'd have cited the 4.2 insulation in the unheated space

[Jerry Peck]

2) It's allowed provided: a) the species is sufficient to support the load;

See link below

b) the size is sufficient to provide at least minimum bearing area;

Code would likely dictate minimum bearing, as would the information in the link below.

c) the grain runs perpendicular to the girder and not parallel with the girder (common sense so the weight of the girder does not split it);

Common sense.

d) that the shim is somehow secured in place so it cannot move out of place on its own (this may not be required in some areas, but it is still a 'smart and common sense' think to do).

Code (depending on where you are - down here, all load bearing paths to the foundation are required to be strapped such that the load bearing path is continuous during uplift) and common sense.

Which of those are are those code requirements and which are "best practice", for example where would I find a table of the allowable compressive loads for various species of wood?

Michael,

Design Values for Joists and Rafters, 2005 Edition, American Forest & Paper Association, American Wood Council: http://www.awc.org/pdf/DVJR_2005.pdf

Used to use the above (an older version, of course) along with 'Span Tables for Joists and Rafters' from National Forest Products Association.

Southern Pine Council offers similar information along with span tables: http://newstore.southernpine.com/images/ref202.pdf

[Jerry Peck]

"best practice",

Michael,

I would stop using the term "best practice" or even "best use and practice" as the "best practice" may be to bring in ..

... an M1A1 Abrams to use as a pier.

I would use "construction basics" instead. When "construction basics" are not followed, problems arise.

I use "construction basics" "basic construction practices" and "common sense".

Builders have forgotten their "basic construction practices" and are no longer building with an understanding of "construction basics", along with the lack of use of "common sense" during construction.

"Common sense" says you do not hang a girder out into thin air and expect it to stay in place. No one needs to have an understanding of code to understand that, it is "common sense".

[Vern Heiler]

Mike, are you sure the other inspector was not saying, "The shim is in direct contact with masonry and does not appear to be treated lumber."?

[Mike Hunger]

Thanks to all for the insight on this post... I got way more than I expected. I am sure this discussion will go on for a while.

FYI - this inspection was for a national relocation inspection company that I do property assessments for.

Vern, the other inspector told me the wood shim was unacceptable - they do not differentiate between dimensional lumber or tapered shims, just wood shims in general. I've never had them bring up the issue of treated vs non-treated.

I believe the practice around here is to construct the piers to the same height as the foundation wall, and then make up the space with the same thickness lumber as the sill plate - usually 2 X whatever.

[Dave Hahn]

Mike...

I've always called them "shims" myself.
My county (Mecklenburg) had put out a Code Interpretation in 2002 calling them shims and allowing wood unless the space was over 4", then you had to use masonry.

Attached here, however, is an interpretation from the NCDOI dated 3/31/2005 calling them "wooden girder plates" (and later acknowledging them as "shims") and allows the use of wood (conditionally) up until a gap greater than 1 1/2 inches inwhich masonry should then be used.

Dave
Charlotte, NC

[Mike Hunger]

Great! Thanks, Dave... that was nagging me.

[Vern Heiler]

Mike HungerI believe the practice around here is to construct the piers to the same height as the foundation wall, and then make up the space with the same thickness lumber as the sill plate - usually 2 X whatever.

Mike, all of the houses I have inspected that have been built since the early 90's, have PT lumber sill plates. The piers have the same PT lumber shims and or metal plates.

The code does not require PT unless 8" or closer to exposed earth on exterior foundation walls but it is a good practice. The PT lumber also acts as additional protection from insect damage.

The other inspector may have a different interpretation of the code, I don't know. We'll ask Jerry--- Hey Jerry, a little help here!

[Jerry Peck]

From the 2006 IRC. (underlining is mine)

- SECTION R319
- - PROTECTION AGAINST DECAY

- - - R319.1 Location required.

Protection from decay shall be provided in the following locations by the use of naturally durable wood or wood that is preservative treated in accordance with AWPA U1 for the species, product, preservative and end use. Preservatives shall be listed in Section 4 of AWPA U1.
- - - - 1. Wood joists or the bottom of a wood structural floor when closer than 18 inches (457 mm) or wood girders when closer than 12 inches (305 mm) to the exposed ground in crawl spaces or unexcavated area located within the periphery of the building foundation.
- - - - 2. All wood framing members that rest on concrete or masonry exterior foundation walls and are less than 8 inches (203 mm) from the exposed ground.
- - - - 3. Sills and sleepers on a concrete or masonry slab that is in direct contact with the ground unless separated from such slab by an impervious moisture barrier.
- - - - 4. The ends of wood girders entering exterior masonry or concrete walls having clearances of less than 0.5 inch (12.7 mm) on tops, sides and ends.
- - - - 5. Wood siding, sheathing and wall framing on the exterior of a building having a clearance of less than 6 inches (152 mm) from the ground.
- - - - 6. Wood structural members supporting moisture-permeable floors or roofs that are exposed to the weather, such as concrete or masonry slabs, unless separated from such floors or roofs by an impervious moisture barrier.
- - - - 7. Wood furring strips or other wood framing members attached directly to the interior of exterior masonry walls or concrete walls below grade except where an approved vapor retarder is applied between the wall and the furring strips or framing members.

To meet *code minimum* (minimum legally allowed to build to), that would not need to be PT (however, it looks like it may be PT). Being PT, if it is, would put it into the:

I use "construction basics" "basic construction practices" and "common sense".

I stated above.

Placing PT directly against concrete or masonry, in any location, *has the potential* to cause wood decay, and any contractor using "common sense" and "basic construction practices", and who understand "construction basics" will recognize that and take that step above code. Does it still "meet code"? You bet it does. Is it required? No, not by minimum code requirements for minimum standard construction, not if that is what you are building.

[Ken Amelin]

2) It's allowed provided: a) the species is sufficient to support the load; b) the size is sufficient to provide at least minimum bearing area; c) the grain runs perpendicular to the girder and not parallel with the girder (common sense so the weight of the girder does not split it); d) that the shim is somehow secured in place so it cannot move out of place on its own (this may not be required in some areas, but it is still a 'smart and common sense' think to do).

Sorry Jerry but - I'm not sure I agree with your statement "underlined & in bold" at all.

Think of this "common sense" issue:

1) Joist support floor loads and their grain is run parallel.
2) Sill Plates support joists and their grain is run parrallel.
3) Girders support the joists and their grain runs parallel.

All of the above are under compressive loads.

[Jerry Peck]

Sorry Jerry but - I'm not sure I agree with your statement "underlined & in bold" at all.

Think of this "common sense" issue:

1) Joist support floor loads and their grain is run parallel.

Parallel to what?

Floor joists are perpendicular to the structural panel underlayment, floor joists are perpendicular (or at 45 degrees) to plank subflooring in older homes.

2) Sill Plates support joists and their grain is run parrallel.

Parallel to what?

Sill plates support floor joists and the sill plate grain is perpendicular to the grain of the floor joist.

3) Girders support the joists and their grain runs parallel.

Parallel to what?

Girders support floor joists, and the grain of the girder is perpendicular to the grain of the floor joist.

Think about it.

[Ken Amelin]

I read the statement as grain that is parallel to the horizon under compression as in floor joists, girt beams, and sill plates vs. grain that is perpendicluar to the horizon as in an upright wood column or end grain under compression.

[Jerry Peck]

I read the statement as grain that is parallel to the horizon under compression as in floor joists, girt beams, and sill plates vs. grain that is perpendicluar to the horizon as in an upright wood column or end grain under compression.

Ken,

Where did you get "horizon" from?

I tried to be very specific in my post with "c) the grain runs perpendicular to the girder and not parallel with the girder (common sense so the weight of the girder does not split it); "

"c) the grain runs perpendicular to the girder ... " " ... and not parallel with the girder ... " " ... (common sense so the weight of the girder does not split it)"

[Jim Luttrall]

Think 3D Jerry. There are two perpendiculars to any beam, girder or joist.
The grain should be parallel on one plane but perpendicular on the other.
I understood what was meant, but there was some ambiguity.

[Ted Menelly]

Think 3D Jerry. There are two perpendiculars to any beam, girder or joist.
The grain should be parallel on one plane but perpendicular on the other.
I understood what was meant, but there was some ambiguity.

Uh Oh, "ambiguity", gotta go look that up

[Jerry Peck]

Think 3D Jerry. There are two perpendiculars to any beam, girder or joist.
The grain should be parallel on one plane but perpendicular on the other.
I understood what was meant, but there was some ambiguity.

Jim,

The 3D aspect is taken care of by the photo. It places one item (in this case the girder) bearing on another items (the shim) and shows that other item (the shim) 'not to be in the 3rd dimension'.

Thus, there are 2 other dimensions left to consider. Parallel with length of the girder in the plane of the length of the girder, or perpendicular to the length of the girder in the plane of the length of the girder.

The 'perpendicular to the length of the girder in a plane perpendicular to the length of the girder' has been eliminated by the photo.

At least in my thinking, based on what was already being shown in the photo (we are talking shims, not studs). I could be wrong ... ... have been before ... ... and will be again .

Addressing "shims" as being tapered and not flat with parallel sides, think mechanical work and shims there. They are flat with parallel sides, in most cases, there may be a few with tapers (can't think of any right now, though).

[Jim Luttrall]

Jerry, what would you get if you cut the "shim" from the end of a stud, across the grain... maybe even a "tapered shim" and inserted it into that space in the picture? Would the grain of the said shim be perpendicular to the girder?
Think outside the box, 3D.

[Jerry Peck]

Jerry, what would you get if you cut the "shim" from the end of a stud, across the grain... maybe even a "tapered shim" and inserted it into that space in the picture? Would the grain of the said shim be perpendicular to the girder?
Think outside the box, 3D.

You would get some slivers which held together, but mostly you would get a splintering mess when trying to shove that in there.

*I am* thinking outside the box.