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sill plates #4821 12/13/06 02:55 AM
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OK, guys, help me decide what to do here...
I'm planning a small shed about 6'x8', and plan to use 6x6 posts (cedar). I would like to fit them into 1/2 lapped sill plates in the corners, but was thinking of using only 4x6 for the sills. But this leaves me with only 2" of lap, and I would like to mortise the lap as well....will I be left with enough meat, or should I get over it and start thinking 6x6 for the sills as well?
confused
*K
And, no, I'm not running it through the Hundegger!

Re: sill plates #4822 12/13/06 05:42 AM
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Hey TG, are your sills fully supported, or are they spanned between pillars? Supporting a floor? If not, you may omit them and place them directly in a saddle?

Brock

Re: sill plates #4823 12/13/06 12:51 PM
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Mark Davidson Offline
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could you expain how you will mortise the lap?
generally lap joints are not mortised.... unless you mean a mortise for the post bottom?
these corner connections could be blind mortise and tennoned with 1.5" m&t...

Re: sill plates #4824 12/13/06 10:38 PM
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Yes, a mortise for the post bottom.
I suppose it really would only need to be a 1" locater peg...

This is what I'm thinking....

Re: sill plates #4825 12/14/06 01:02 PM
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go for it, your drawing looks workable.

Re: sill plates #4826 12/14/06 02:11 PM
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TG:
The corner joint you use will depend on whether or not you are a Sobonite or a Bensonite laugh

The drawing you have posted, IMHO, is leaning towards the Bensonite side of timber framing.

I consider this joint a Sobonite joint (although it is drawn with 8x8s and the layout is 2" and 2", the principal is the same with 6x6s, except the layout is 1.5x 1.5"...


Jim Rogers

Last edited by Jim Rogers; 09/27/17 01:11 PM.

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Re: sill plates #4827 12/15/06 02:01 AM
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northern hewer Offline
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Hi all

Jim is on the right track in my books, the only thing that I would add is that the tenon and the mortise be placed at least centrally on the timbers concerned, and the tenon on the vertical post be only long enough to not quite touch the through tenon when it sits down in its top mortise

NH

Re: sill plates #4828 12/15/06 04:18 AM
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Thanks for the replies.

I never really considered Sobonite vs. Bensonite style, I just want the joinery done well, and it doesn't need to be too complicated as it's a quick project that will need to be cut in a day or so. So, ya, Benson.

But I do need to know if I can use 4x6's for the sill plates.

When I have the time, which I'm hopeful will be this summer, I will do another small frame with more of a Sobon/Scandinavian influence (I'm going to start working on it soon). Then I'll be back with more questions.

Jim - was that a stock drawing of yours, or did you manage to whip it up just for this? I'm impressed! It pales in comparison to my 2 min. doodle...
*K

Re: sill plates #4829 12/15/06 04:32 AM
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Quote:
Originally posted by Timber Goddess:

But I do need to know if I can use 4x6's for the sill plates.
Hard to say: Are the sills supporting a floor load or just there to tie posts and nail wall planking to? Are they fully supported or only where there are posts?


Raphael D. Swift
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Re: sill plates #4830 12/15/06 05:05 AM
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The latter and the latter to both questions.

Re: sill plates #4831 12/15/06 05:52 AM
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Vertical load certainly isn't going to be a problem, didn't even put a blip on my spread sheet with the full weight of the walls bearing on only the sills. I also used EWP numbers as they are the weakest values I had handy.

As long as your 'Bensonite' post tennon is 4" long (minus relief for sill shrinkage) so it engages both timbers you will be fine with the 4x6. Just take care not to torque it during assembly. I'd tuck it inward on the post to allow as much relish as possible for the sills' end grain.

Are you doing this square rule?


Raphael D. Swift
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Re: sill plates #4832 12/15/06 02:36 PM
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Quote:
Originally posted by Raphael D. Swift:
Are you doing this square rule?
I might...It depends on the $$ vs. time thing. Right now I'm just floating ideas around.
*K

Re: sill plates #4833 12/16/06 02:05 PM
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TG: That was a stock photo of a drawing I did for one of my workshop frames.
When I print a 2d drawing of a joint I like to add a 3d view to show the student what the whole thing will look like.
NH: I understand your point. But this frame has several "general frame rules", and one rule is that the layout of tenons and their mortises are 2" off the reference face and then 2" thick/wide. So with this cross sill (the one with the tenon) connecting to the long sill (the one with the mortise and floor joist drop in pockets) joint, this rule has been met.
Another rule for this frame is that all joints are reduced to the next 1/2" smaller in size (of the actual timber). This is shown by the reduction of the tenon on the inside of the frame.
These two rules are just some of the rules we use when doing square rule joinery, on non planed timbers.
(I'm just posting this as some general info for others not familiar with square rule joinery).

Jim Rogers


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Re: sill plates #4834 12/16/06 07:01 PM
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You guys rock!
Thanks for the input, I learn so much from your conversations - valuable stuff!
*K

Re: sill plates #4835 12/18/06 01:59 AM
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Hi Jim and all:

Great response Jim but I have just one last comment about the corner joint.

Could you tell me why in the majority of cases that the historic frames that I have examined use a half lap fastening on the corners, rather than just relying on a 2 " tendon to hold things together.

I always used the half lap connection because it was what was used in all the original structures that I reproduced , and it seems to me that the half lap would be stronger equalizing the relish left on both timbers

What do you all think

NH

Re: sill plates #4837 12/18/06 04:30 PM
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NH:
most of the old frames around me use the m&t at sill corners....

Re: sill plates #4838 12/19/06 03:02 AM
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Hi Mark and all--good discussion and input

that is very interesting Mark, but there you go, no one should say only one way to do everything, right!

Many of the barns that I have inspected had bottom mud sills 12" square.

(this is just a comparison)

So if you used a mortise and tenon attachment at the corners, the strength of the corner would have to rely on the strength of a 2 by 11 tenon, or 22square inches of wood.

if you used a half lap the strength of the corner would rely on a 6 by 11 or 66 square inches of wood or 3 times as much holding power.

This is just my observation, I am sure that the corners were done in both methods, I have never noticed or seen the mortise and tenon used at the corners, but then there is alot of things that I haven't seen, it is nice to hear that you have seen this method used and share it here with everyone.

NH

Re: sill plates #4839 12/19/06 03:16 AM
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Quote:
Originally posted by Derek J Swanger:
4 by 6 is fine for sill plate TG. Less money and still a timber.
Bingo! That's what I was looking for! (Found out some great stuff along the way, though!) That along with Raphael's spread sheet works for me.
Any disputes....?
Ok. So then, what to do about the floor....? :rolleyes:
I'll get to that later.

Re: sill plates #4840 12/19/06 11:46 AM
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couple of things
most of the old frames I've looked at use a m&t that is 1/4 the size of the timber, so in a 12x12 I would expect a 3" tenon, the most common size barn timber around me is 10x10, most often with 2 1/2" tenons.
The other thing is that I disagree that a 4x6 is a timber. It needs to be 5" thick before it is a timber. Just a technical point.

Re: sill plates #4841 12/19/06 11:50 PM
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here...let me get out my timber pencil and jot this down... wink
OK - so, in order for this shed to classify as a timber frame as opposed to a common stick frame, I should use 5x6....aaawwww, now what do I do???

Re: sill plates #4842 12/20/06 09:38 PM
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NH: How is a half lap joint held together?
I understand about how you've figured it is stronger, but what holds it together? With a mortise and tenon joint the peg holds the cross sill from pulling out of the long sill.

Jim Rogers


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Re: sill plates #4843 12/20/06 09:40 PM
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Quote:
Originally posted by Timber Goddess:
here...let me get out my timber pencil and jot this down... wink
OK - so, in order for this shed to classify as a timber frame as opposed to a common stick frame, I should use 5x6....aaawwww, now what do I do???
Call it a plank frame..... laugh


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Re: sill plates #4845 12/21/06 02:17 AM
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Hi Jim and all:

First of all let me say that I am only stating techniques used by timberframers from years gone by. I have examined many but not by any means all of the standing frames in my immediate area, but those that I did I paid particular attention to details that was necessary for authentic reproduction, and this included the pinning of joints.

One thing that I have noted is that framers varied widely in their style of pinning and attaching joints

As far as the fastening of corner joints in the bottom mud sills, I did the best I could to duplicate the methods of attachment. What I did to varify the pinning of the corners of a standing frame that I was to reproduce, was to slide in a thin blade and verify the position and number of pins used. In most cases the corners were held with at least (2) 1.5" oak pins, the odd time (3) 1.25" pins staggered slightly. these pins were placed about 2" from the shouldering, leaving enough room on the flat surface, for the mortise of bottom tennon of the vertical corner post.
In most cases the long side sills would pass over the shorter end sills.

It is always a good idea to bore a drain hole in the bottom of the mortises along the bottom sills for drainage should rain water happen to enter the mortise for some reason.

I hope this explanation helps to clarify the techniques that I have to offer on this forum.

NH

Re: sill plates #4846 12/21/06 03:33 PM
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Quote:
Originally posted by northern hewer:
It is always a good idea to bore a drain hole in the bottom of the mortises along the bottom sills for drainage should rain water happen to enter the mortise for some reason.
I like that! This is also the reason why I'm going with cedar...tends to last through the rain. I recently pulled 4 cedar garden posts out of my mothers yard - they had been in the ground since the house was built (1898), and had minimal rot on the butt ends...!

Re: sill plates #4847 12/24/06 11:02 AM
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Dear Timber Godess,

The significance of your post cannot be allowed to pass without comment and note. If your claimed service age for this post is true then this must be one of the longest ground contact timber decay tests on record.

Can I appeal to you to photograph this piece please and do a thorough post mortem on same i.e. check same for timber conversion marks, try and identify original place in tree and size of tree from which it was converted, average growth ring patterns, species (WRC ?)and note the ground conditions e.g. clay, sand, gravel plus annual rainfall and temperatures.

Please let us know more about this post.

Regards

Ken Hume


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Re: sill plates #4848 12/26/06 01:21 AM
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Yes, Ken, I suppose that the claim of the wood being as old as the house itself may be pure speculation...
I have no photos (this was about 4 yrs ago) but the details are this: My husband and I were digging a new garden. As we were removing the top soil we hit quite a few rocks, and a few treasures; some broken porcelain and an old twisted silver spoon...and a chunk of wood. As we dug deeper to remove the wood (about 4x4) we found it was set into a hole about 3' deep, filled with large rocks. We pulled it out; the bottom and the outside was soft and covered with dirt, but only about an inch deep. The top was similar. It was WRC. The soil is mostly red clay. We used it for a tomato stake.
We pulled another one out from a different corner of the yard...it was rotten through, but in that part of the yard the soil was quite sandy.
The reason I speculate about the age was that the neighbor, an elderly woman whom the street is named after, commented on the fact that she had never seen a fence in the place where we were digging, and she had lived in the house across the street all her life.
Apparently I have a bit too much idealism, in that I tend to believe most of what the old timers have to say without analyzing the reality. ("Well, the lady said such-and-such, and she's an elder, so it must be true...")
I was also going to tell you all about the beautiful pinkish brown cedar shakes found on the bottom layer of the roof we were replacing. They still smelled fresh cut, and had also been there since the house was built.
But, once again, I have no way of verifying that...
wink

Re: sill plates #4849 12/26/06 01:58 AM
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Ken and TG

This story makes perfect sense to me. Wood rot is caused by fungi. Before fungi can colonize wood, four requirements must be met: an oxygen supply, temperature in the 40 to 100 (F) range, a supply of sufficient moisture, and a food source (wood). Infection can be prevented by eliminating any one of the requirements. What has happened in this case is that the posts rotted at the margin where they enter the ground and are in contact with the soil but still have access to oxygen. The bases that you found were cut off from the oxygen.
I have seen this phenomenon with WRC fences before. The post has rotted off and you think you are going to replace it where it was, only to find the old post base intact in the ground.
It should also be noted that the tannins in Red Cedar that make it rot resistant accumulate over time so that old growth heartwood is vastly superior in rot resistance to much of the cedar available now.
My bet is those post stumps are as old as you think. Unfortunately there is no lesson here for building because there in no way to avoid the rot at the transition

Re: sill plates #4850 12/27/06 02:58 AM
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hI ALL

well I have one also to tell in this regard:

My father who if he was alive now would be 108 yrs young, and one day (1959)as a young man--I was about 20)-- he and I passed by an anchor post (red cedar) set in the corner of a field where he was raised, and he related to me that his older brother had dug the hole and put that post in when he was about 6 years old.

Now this anchor seemed to me to be in pretty good shape and from my calculations about 50 years old at that time. That anchor was removed about 10 years ago by a new owner of the property (1996), and I noticed the removal of it. The lower end was in very good condition, while at ground level it was half eaten away by decay.

The anchor was stoned in if this is of any help as was all anchors that were installed properly at that time,

NH

Re: sill plates #4851 12/29/06 01:52 AM
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I am thinking the longevity of the posts set in stones has to do with moisture. I have found old (date set unknown) red cedar boundary corner posts that were almost completely gone above ground but still solid in the hole. They were scribed with owner name and lot # ....which to my knowledge no one does anymore. Packing rocks around the post allows the water to drain away.
So if we make the sills and posts out of rock we should be fine....oh wait, we would have to be masons to do that wouldn't we?

Bob

Re: sill plates #4852 12/29/06 09:23 AM
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Hi All posters,

This is a fascinating topic.

I have often toyed with the idea of what it would take to design an all wood foundation and the posts received to date seem to provide both encouraging and cautionary advice.

Most old timber buildings here in the UK have long lost their timber sills with many buildings showing evidence of being righted and underbuilt with more durable materials like brick and stone.

Much earlier, building techniques did employ timber in direct contact with the ground. For example in Scotland and Ireland we have crannog buildings which were built on piled foundations in shallow loch waters with a linking causeway to shore. Below water line some of the timber piles (alder) can still be seen today several thousand years after driving same into the mud.

We have examples of early post (wind) mills where the trestle cross trees and quarterbars (oak)were buried and backfilled to help provide greater stability to the mill. The Saxons were great believers in using earthfast posts and remnants of post circles are frequently encountered

Venice is built on (larch) timber piles.

I accept that the ground / air interface is the problem to be overcome but could we not employ easily replaceable or sacrificial pieces that spanned this vulnerable area made from highly durable timber like cedar, locust, oak, etc.

There also remains the question of treatment and in times gone by charring was employed to good effect as was the application of pine pitch.

I would be keen to get rid of the necessity for the embodyment of high energy concrete foundations.

Any ideas ?

Regards

Ken Hume


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Re: sill plates #4853 12/30/06 01:49 AM
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Ken
Many of the old mill dams (1800's) were infilled cribs and one can still find the sound timbers in the rivers.
I have read of using pressure treated plywood for foundations but do not know the life expentancy.
Burning the wood would remove whatever it is that bugs and microbes go after...sugars?
We USED to soak our fence posts in old motor oil and they seemed to last forever. It seems the more we try to defeat the natural order of things the worse it gets. A well layed stone foundation wall with well planned drainage is probably the lowest energy input system you will find but it is very high on the labor scale(another form of energy !)
What about rammed earth walls with well planned drainage?
Bob

Re: sill plates #4854 12/30/06 03:36 AM
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While it may be possible to develop a good wood foundation system it would not necessarily work well in all conditions. I can see using a stone or masonry capped piling if dealing with soft soils or deep frosts. Where I am in Western Washington we have shallow frost and soils that may or may not drain (glacial tills and outwash). We also have more varities of mushroom than anywhere else in the world and same conditions that make that possible also cause wood rot...lots of it. I would consider stone but we also have seismic issues...so..concrete is my friend.
Having said that, I'm sure that Bob and NH are right that the stone set posts last because air moves around the stones. I suspicion that this works very well for a while but what happens is that a debris cap forms and the rot starts at this "rot gasket" (local term).
The one condition that compels me to think of sinking posts is to develop lateral strength (the ol' vertical cantilever) The last time I had to do this I thought of a possible solution (after the fact) which was to wrap the post in corrugated metal roofing, set this in an oversized hole with gravel in the bottom and pour concrete for bearing to undisturbed soil. If the metal was extended above grade it might at least stave off the debris cap effect.

Re: sill plates #4855 01/02/07 11:28 PM
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Dear TG,

the 4x6 will work if the plate is fully supported, say you are building of a concrete slab. If you are using piers then you might consider something a bit heavier.
If you end up using the 4x6 then you just might have to put the floor joists on top of the plate. Although if you have a slab that will not be necessary.
The lap joint will work just fine and is easy enough to cut. If you use a through tenon on your post that will also serve to secure the lap joint. There is also not as much ( almost none) tension on this joint anyway. Not compared to a tie beam.

Regarding the dimension and if one could call it a beam. It certainly is not but what you are going to be building is still a timber frame. So no worries there about stick/beam sizing. Many/all braces used in timber frames are not actually a beam/timber so why worry about a smaller sill plate?

Edited for additional info

Re: sill plates #4856 01/07/07 05:17 PM
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Quote:
Originally posted by Timber Goddess:
Quote:
Originally posted by Derek J Swanger:
[b]4 by 6 is fine for sill plate TG. Less money and still a timber.
Bingo! That's what I was looking for! (Found out some great stuff along the way, though!) That along with Raphael's spread sheet works for me.
Any disputes....?
Ok. So then, what to do about the floor....? :rolleyes:
I'll get to that later.[/b]
How do I get Raphael's spread sheet?

Re: sill plates #4857 01/07/07 11:15 PM
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@ Peg_1,

Quote:
Ok. So then, what to do about the floor....?

You could, similar to stick framing, put a 4x6 on edge and peg your joists into them. Kind of like a rim board. Then you can put your 4x6 plate on top of the already framed floor. Just an idea.

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