# Plinth Block



## dharmabum

I'm trimming out a house for a customer and they have requested plinth blocks on all door casing. This trim out is a modified craftsman style with 1x4's. I normally bring the plinth up to the jamb extension with no reveal. The customer is claiming she has never seen them done this way.
Any input on what is the norm here?


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## Big Dave

First off, welcome to the forum. I do it the same way as you described. If you give the block a reveal then you have to give the casing more reveal which usually means your on the very edge of the jamb and it makes it hard to nail.

That being said I would do my best to make the customer happy, whatever that takes.


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## BULLHART

I do it the same way.


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## dharmabum

Thanks for the replies. I'll stick with the way I've always done it, as that seems to be the consensus. I am always worried about splitting jamb extensions when you have too much reveal.
Again, 
thanks


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## clampman

I think it depends entirely on what kind of plinth you are using. For instance, mine are always installed vertically and are 1/4 to 5/16ths wider than the casing. They are designed so the casing sits centered on the plinth. So I can do an eighth reveal on the plinth and have a quarter on the casing.

If I have to hold the plinth slightly closer than an eighth, I will.

Regards,
Jimc


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## dharmabum

clampman said:


> I think it depends entirely on what kind of plinth you are using. For instance, mine are always installed vertically and are 1/4 to 5/16ths wider than the casing. They are designed so the casing sits centered on the plinth. So I can do an eighth reveal on the plinth and have a quarter on the casing.
> 
> If I have to hold the plinth slightly closer than an eighth, I will.
> 
> Regards,
> Jimc


Jim,
Do you use biscuits and glue at the joint between the Plinth and the casing? I always have, but am beginning to think I'm just adding an unnecessay step.


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## clampman

No, I never have used biscuits there. I really don't think its necessary, at least when the plinths are at the bottom. I could see how they might help out with allignment if you were using corner blocks at the head and legs.


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## Suz

When we custom made the plinth blocks for installation I asked the carpenter he said he keeps a 1/4" reveal with the casing. I then figured 1/8 inch reveal on both sides of the plinth blocks.


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## nywoodwizard

I have installed and made hundreds and left them all flush,except for certain exceptions,i don't think the reveal on the plinth bock is as important if the openings will have doors,however it does look better for all to be revealed if being painted ,because it leaves a flush seam which does not look to appealing,if i had to do alot of casings on jambs that won't have doors ,i would put the reveal on the plinth block.the same applies to some windows with rosettes,if its a large window with a radius top and a continual jamb,the rosette between the transition looks bad flush.i hope that makes sense.


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## RippySkippy

I don't want to hijack the thread but have some ?'s releated to plinth blocks, what is the typical height and width?

Just a bit of background...my wife and I are buiding our own ICF home, we've done all the work except for a few things requiring more labor or equipment than we have.

I'll be using roughly a 1x4 for the casing, and about 1x5 for the base. I figured I would use a plinth block that would be about 8-3/16 tall, 4-1/2 wide and 5/4 thick. Originally I was going to make the reveal the same as the casing, but I'm reading here that isn't correct. 

Also, I have 2 doors, one 36" and one about 60" that will be cased only no doors. Do I wrap the plinth block aound as part of the casing or just put the plinth block on the wall sides only?

Take a look at the attached PDF, it has all the dimensions I'm considering.

I'd be interested in others thoughts.

Rip


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## TexasTimbers

RippySkippy said:


> what is the typical height and width?
> Do I wrap the plinth block aound as part of the casing or just put the plinth block on the wall sides only?
> I'd be interested in others thoughts.
> 
> Rip


I have only used plinth blocks on one job in the past, but plinth blocks come in every imaginable style and size. Pick what suits your eye and don't worry about what others think ought to look good. 

AFA wrapping the block my preference would be on the wall only no wrap.

Those are my thoughts.  

BTW welcome to our cyber haven.


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## Big Dave

RippySkippy said:


> I don't want to hijack the thread but have some ?'s releated to plinth blocks, what is the typical height and width?
> 
> Just a bit of background...my wife and I are buiding our own ICF home, we've done all the work except for a few things requiring more labor or equipment than we have.
> 
> I'll be using roughly a 1x4 for the casing, and about 1x5 for the base. I figured I would use a plinth block that would be about 8-3/16 tall, 4-1/2 wide and 5/4 thick. Originally I was going to make the reveal the same as the casing, but I'm reading here that isn't correct.
> 
> Also, I have 2 doors, one 36" and one about 60" that will be cased only no doors. Do I wrap the plinth block aound as part of the casing or just put the plinth block on the wall sides only?
> 
> Take a look at the attached PDF, it has all the dimensions I'm considering.
> 
> I'd be interested in others thoughts.
> 
> Rip


Typically I like the block to be a 1/4" wider than the casing and an inch taller. If you go taller than that they start looking too long and skinny and don't fit well. If you go any wider then you start having issues with the reveal.

I also agree with Texas Timbers, only on the wall sides and not in the opening itself.


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## clampman

Ditto what Big Dave said on the width. The reason is that if you go much wider, the casing can miss the jamb. Ditto on the wall only.

I assume Dave is talking 1" taller than the base cap. I generally go 
1 1/4" taller than the base cap - especially if the floors are out of level here and there. That extra 1/4 seems to make it less noticeable across the width of a door. But as Dave said, it's really up to what you think looks best.

One thing to remember - though with 5" base you shouldn't have a problem - is that your bottom door hinges have to be completely above your plinth blocks. At 5/4" thick they can interfere with the hinge barrel unless you hold the plinth way back from the jamb edge. Then you are back in the same predicament where the casing will not hit the jamb.

By "missing the jamb" I mean making it very hard to nail the casing to the jamb. What many people don't consider, including many carpenters, is that the casing is an integral, structural part of the door system. It provides nail strength in sheer to the jamb as opposed to nails in tension which do basically nothing after a few years. 

The closer the casing gets to the outside of the jamb, the weaker that joint becomes - doubly so because smaller nails are required to prevent them from blowing out throuigh the face of the jamb when nailing the casing on at such an angle.

Any finish carpenter with historic restoration experience will confirm this I am sure. Like Big Dave say 1/4 wider on the plinth is usually plenty. I ocassionally go 5/16th in situations where the casing is pretty massive - but no more than that.

Have fun.


I just looked at your PDF. With regard to the plinths, I would make them 7/8" x 4 1/4 x 6 1/4 presuming a 5" base. I would put a 45* chamfering bit with a bearing, and run a 1/16th to 3/32nd chamfer along the top of the plinths on three sides, leaving just a hint of flat exposed where the casing sits centered on top. This will allow the paint to seal between casing and plinth so you do not get a part crack / part no crack between plinths and casings all over the house. 

If you were to apply the Golden Mean to your plinth the supposed perfect size would be 4 1/4 x 6 7/8. However, that would be too tall for your base size, in my opinion, and the Golden Mean cannot apply to everything anyhow..

The true test will be when you make a mockup of each (the way you have drawn it and the way one or more of us has described) to see what looks better to YOU. We don't have to look at it, no matter what you do.

Regards,
Jimc


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## Krazy johnni

After looking at your pic *RippySkippy *one thing you might want to consider is moving the plinth blocks on the main door so that they line up with the window casing. Then run the out side window casing all the way down to the plinth block the area under the window should be the same colour as the trim making it seem like one unit. Just another option to think about.


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## RippySkippy

Thanks to all that chimmed in...it looks like it's time to get off the computer and get out the t-square, scissors and construction paper for the mock up.

I really appreciate the input on the sizing...there's a couple of details that I hadn't picked up on, like centering the casing on the plinth. I hadn't thought about the height of the plinth interferring with the hinges, and I'll kick around the height thing a bit more. FWIW -- The house has 9' ceilings with trays in the MBR and LR up to 10'.

The window/door/window combo is on the "back side" of the LR, and opens into a covered porch. While I appreciate the input *Krazy johnni*, I have an outlet in the middle of each window in the small section of wall below it. I thought if SWMBO decided to put foo in the window sill, I didn't want cords running all over. Remember ICF = deep jambs (9") = shelf.

Thanks again for the input, and I'll get the scissors out and start mock this up.

Rip


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## clampman

Well, it's always a tossup how people will react to suggestions, but since Kraziy J started, I will risk continuing.

I would also do as KJ suggested, and have in fact done so more often than not. My guess is that you probably have plenty of room between door and flanking windows for a full width casing. 

Entry doors are "specials" (even if they go out back) and often do not follow the trim details of other doors and windows. Running the casing to the floor on the outside edges of the windows would, I believe, give you a much more balanced look. I would use plinths on both sides of the windows - unless the door to window casing is real skinny- which I doubt.

That will not affect the outlets - which I would try to get into the baseboard instead of up the wall throughout the house, unless it is already too late. 

I would also forget the panel above the window with the divided lights.

You might also think about a little taller baseboard as well, since you are going with a pretty generous head casing.

Regards,
Jimc


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## RippySkippy

Hey clampman,

You know this life is too short to get bent out of shape when asking for suggestions! As long as I can remember, I've always wanted ideas and suggestions...fodder for thought. Generally I learn something along the way as well...and I really like to learn new things.

The outlet placement, too late...we drywalled last week. I would guess that I could paint the cover plate and outlets similar to the trim under the window area.

You're right on the wall, there must be 6 feet or so on each side. The only place that's a bit narrow is the space between the french doors and the windows on each side...it's RO is is only 3". So that piece will have to be narrower than the side casing...but I don't think that will be all bad as there's lots of weight with the rest of the wood in the windows.

You mention forgetting the panel above the divided light windows...are you talking the transom, or the head casing? Are you saying the head would be the same as the side casing? I've kicked this around a lot...and I'm guessing I won't be done til I'm done trimming! 

Thanks again, and I really appreciate the comments/critique.

Rip


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