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Brace Layout Question and Answers

Started by Jim_Rogers, June 22, 2004, 01:51:34 PM

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Jim_Rogers

Laying out a Brace Corner
Part one.
The other day a timber framer sent me an email asking me:

"Hey Jim, Quick question...do you know of a publication that provides detailed layout
and cutting procedures for the wind brace joints? This is the only one that
is making me a little nervous! They have to be right."


My first response was to ask him what he meant by wind brace.

He said: "Other terms I guess would be "corner brace" or "knee brace". A 45 degree
brace from posts to tie beams, to plates, and to perlin plates etc."


Here is my advice. The most important thing to remember is that brace layout is done correctly.

The brace timber itself is the hypotenuse of the right triangle. And this right triangle is an equal lateral and equal angular triangle. That is that both "legs" of the triangle are the same length, and the two angles are both 45°. (I'm sure you knew that).

The key to laying out a pair of brace pockets on two different timbers so that the brace fits correctly is the "starting point" or the corner that makes the right triangle.
This point is where all the brace measurements will start from. That is, all of the braces that go from the same size post to the same size tie, in each bent of a frame.  And in every bent of that frame. So that they work and look correct from opposite side of bent to opposite side of the same bent. And that all braces will be the same size (if that is your intention).





Sorry for the low quality of this drawing. But it's to show you how a brace corner should look. And if you don't have a drawing showing you the brace layout, then you should make one and use it each time you need to figure out where the starting point is. Then you can refer to the drawing and it will help you to understand the layout. This drawing shows a 36" brace layout.

Now how do we figure out where this "starting point" is?

We have some answers already. First what is the frame's convention, in regard to sizing of joints?
If the joints are framed to the next 1/2" smaller timber then the brace pocket has to be housed back to the next smaller 1/2" from the full dimension of the timber. At both ends.
So if you were to draw a line on your timber, with a pencil at a distance ½" under the full dimension, of your timber, from the layout edge towards the corner on either timber the post or the tie, these lines would be the leg of the right triangle. Now where these lines meet when the two timbers are connected is the starting point.
In the drawing below the full dimension of the post is 8". The brace layout line would be drawn at 7 ½" from the layout edge of the post. The tie beam is 10" tall, and the layout edge is the top edge. The brace layout line would be 9 ½" down from the top of the tie beam. Such as this:





And then you layout your brace pocket location, in this case 36", like this:





Now this is all great and well, when the pieces are all assembled but we have to layout these brace pockets on the tie beam and the post when they aren't all assembled.
So let's look at these apart.


Next posting will show more........


Jim Rogers
Whatever you do, have fun doing it!
Woodmizer 1994 LT30HDG24 with 6' Bed Extension

Jim_Rogers

Laying out a Brace Corner
Part two.


The next thing we have to look at is where the starting point is when the pieces are apart:





If you can refer to the drawing and it will help you understand where the starting point is.

The drawing will tell you where the brace pockets are. Note that all brace pockets are laid out from the over all dimension; in this case it is 36", back towards the starting point. This is the most common mistake that beginners make is to layout the brace pocket on the wrong side of the 36" point.





(Caption in photo reads: Because the housing is a 1/2" on the braces and the housing is 1" on the tie to post, the starting point is 1/2" off the housing on the post, and 1/2" off the shoulder on the tie. If your tie is housed down 1/2" at the tenon that joins with the post then the starting point is on this line.)

Also you have to understand how to layout the 45° angle cuts on the brace to make them the correct length to fit into the corner and not be two long or two short.

If you make the brace too long, this error will be greatly increased because of the lengths of the "legs" of the triangle. And other parts of the frame will be affected.

If you make the brace too short, this error will affect the braces' ability to do its job which is to stop the frame from racking when wind load is applied to the structure.

More next posting.......

Jim Rogers
Whatever you do, have fun doing it!
Woodmizer 1994 LT30HDG24 with 6' Bed Extension

Jim_Rogers

Laying out a Brace Corner
Part three.

You have to understand how to layout the 45° angle cuts on the brace to make them the correct length to fit into the corner and not be two long or two short.

The next thing you have to figure is the brace length, in inches and sixteenths so we can use our tape measure and or rulers to lay it out. So we use the formula a2+b2=c2. So what that means in this case is (36"x36") + (36"x36") =? Or (1296) + (1296) = 2592. In order to get the brace length we now need to know what is the square root of 2592? The answer is 50.9116 in decimal inches. Now that we have that answer, we need to convert decimal inches into inches and standard sixteenths. How do we do that? Well, first of all would just drop the 50" for now and let's look at .9116 and let's convert that to 16ths so you and use your tape measure or ruler which is has inches divided into 16ths. You do that by multiplying that number (.9116) by 16 (and don't forget the point), and you'll get 14.5856. This is 14.5856 16ths. Next round off or up whatever it needs 14.586, then 14.59, then 14.6, then 15. So that's 15/16ths of an inch (it's better to have your braces a little long and trim later than to have them short and have to shim them.)

Add back the 50 inches we dropped for the moment, and we now know that the brace length is 50 15/16". This is the distance from point to point on the hypotenuse of the triangle. But the triangle hypotenuse line is not on the face of the brace, as the triangle is set into the tie and the post by the housing set back.

So we have to set back this line on the face of the brace in order to locate our two end points of the hypotenuse. If we don't set this line back then the surface of the brace won't be flush with the surface of the post or tie.

This set back line is drawn 3/8" off the layout face of the brace, which is the outside of the brace, with a pencil, on each end of our brace stock:




Then you select a point at one end of your brace stock, allowing enough room for the tenon, and measure from that point on the 3/8" line 50 15/16" and create another point. And mark these two points with a pencil on this 3/8" line. These points are the ends of the hypotenuse. The two 45° lines that create the shoulder line and the tenon bearing end line pass threw these two end points. We usually layout one end first and then the other. That way you can see which side of the brace stock each line has to be on in order for both ends to be mirror images of each other.

You start by making a 45° line threw the point for the bearing end of the brace, number one shown below.





Then you draw a 45° line threw the same point making line number two (shown above). Each time you do this the reference face is the outside of the brace, which is the side the 3/8" line is on, not the inside of the brace. That means you hold your combination square or your speed square against this layout face.

Then you measure up line one the length of the tenon (in the example above it is a four inch by six inch brace with a two inch thick tenon, offset two inch from the layout face and the tenon is three inches long).

And make a line parallel to line two for the end of tenon line. Line number two is really your shoulder line; this line is only cut the depth of the shoulder or the depth of the offset which is two inch deep in this case.

Now that you have these three lines drawn on your rough stock you need to draw more lines on both ends of line one and line three down each side of the brace stock using a speed square or a combination square from this layout face. Line two will be drawn down later, not now.

You can then connect the lines dropped down the sides of your stock that is the end of line one and three on the back side of the brace.

Next, you need to make some cuts to expose the end of the tenons and so you can make more layout lines.

The procedure for cutting a brace is to cut line three first. This will remove a lot of waste wood and this line isn't that important as it's the end of the tenon and maybe cut back later, depending on your mortise pocket.

Once you have cut line number three, you cut line number one. This line is called the bearing surface or bearing end as this is the end of the tenon that will be in compression when the building rocks in the wind. This line has to be very accurately cut. No mistakes not under, not at the wrong angle. It can be cut away from the line but then you'll have to "pare" to the line and make it correct. We score all lines with a knife first before we cut with a saw, to prevent the wood from tearing out and help make the line straight and true.

Once line number one has been cut you'll have the end of the brace stock to draw more lines on. Next you draw or drop line two down the thickness of the offset which is two inches on each end. And then connect the ends of these two dropped lines around the end of the tenon. This will show you the amount of wood that has to be removed to make the tenon. As we do layout work like this we mark all waste wood with "X"s so that we know what parts are waste, and what parts isn't waste. We also mark on the end of the tenon the word "tenon" so we know that this part is not suppose to be cut off.

After you have marked the dropped lines of each end of line two and have connected them and marked the waste wood and scored line two all the way around; you cut line two, with a saw. After you have cut line two, the shoulder cut, and you don't cut it any deeper than the offset two inch, we usually chisel off the waste wood.

Now some people here, at my workshops, have just taken a saw and cut the waste wood off, but more times than not, they have made a mistake and cut the tenon line wrong and therefore have made the offset wrong, usually too thin. So we chisel it off.

Start by clamping the brace onto a sawhorse and using a 1 1/2" or two inch chisel and a mallet, chop off some of the waste wood. Now when I say chop some off, what I mean is you take off just a little maybe 1/4 to 1/2" from the top corner down, then move over and take some off the corner on other side of that tenon. Take the waste wood off the side of the tenon working your way down to the tenon face slowly and evenly so that you don't make your tenon face too deep or too shallow. You can hang your framing square on the shoulder line to gauge whether or not you've got the tenon trimmed down enough.

These procedures need a series of step by step photographs and maybe next workshop I can take some to show you.

Once you have the tenon face trimmed down to two inches off the layout face you can flip it over and shave off the back side with a hand plane until the tenon is two inches thick, which is if your brace stock started at 4 1/8" thick. That's what we do and this makes the back side flat and smooth.

If your brace stock is only four inches thick be careful as you cut the tenon face not to make the tenon too thin. It's better to start with thicker stock then thin stock.

If your brace pockets are centered on the post it's done a little bit different.

Once you have one end done you do the other end the same way but be careful not to cut your shoulder line to short or your brace will be too short for your housing.

That 3/8" offset line on the braces only works if the housing is 1/2" if the brace housing is one inch then the offset line is 1/2".

Also, even though line number one doesn't look like it lines up with the end of the tenon; it does that just because of the angle of the camera taking the picture in the rendering program.
Here is another isometric view:




When you establish frame conventions, such as two inch off layout face, and two inch thick tenons, this is also a way to remember what order you cut things. First you establish the tenon face two inch off the layout face and then you make the tenon two inch thick. That way you shave off the thick part of the tenon from the back side making it thinner, not shave off the layout side moving the brace closer to the outside.

It's important that once you've established that two inch offset you don't shave any more of that side, as it will move the whole piece towards that side, and that's something you don't want to do.

Read it over and ask questions.

Jim Rogers
Whatever you do, have fun doing it!
Woodmizer 1994 LT30HDG24 with 6' Bed Extension

Kirk_Allen

Jim,
Thanks for all the info.  Sorry its taken so long to thank you but I guess I have spent to much time on other parts of the FF.

I bought my mill for the purpose of building a Timber Frame home in Hains Alaska.  I am now at a point where I need to lay out some plans and start cutting some beams.

Im sure I will have many questions as I am slow to learn from reading.  I do much better hands on.

Thanks for sharing you knowledge.

Kirk

beetle

Jim..Thank you!

My braces and pockets came out right on the first try.
 A couple questions:

When you have brace pockets on opposing sides of a post, do you cut a through mortise or two blind ones leaving a little stock in the center? My posts a 8"x 8" with two 3.5" deep pockets which includes the 1/2" housing depths.

When pinning a brace with a 2" offset x 2" tenon, do you pin through the entire post ?

Again, thanks. I could not have done it without the info you provided.

Jeff
Too many hobbies...not enough time.

Jim_Rogers

Jeff/Beetle:

When you layout a brace tenon you usually lay it out for a full inch measure and then after all is done you trim it back one eight of an inch.

In the frame that we are about to raise here at my sawmill yard, we have 3" tenons on the braces cut back to 2 7/8". And mortises that are cut to 3" deep from the should line, hopefully not cut much deeper but they can be up to 3 1/4" deep from the shoulder. This gap is to insure that the tenon doesn't bottom out in the mortise when everything dries.

The method the brace mortise is cut will determine if the brace pocket will be a threw mortise or a blind mortise. If you are using a chain mortiser, then most likely it will be a through mortise. If you're using a boring machine or power drill, chances are then they mortise will be just the depth it needs to be.

Personally I feel if you can leave the wood in between the mortises, I would. Every bit will help to make the post stronger.

All peg holes are always drilled from the layout face. All pegs are driven from the layout face.

If there isn't a timber blocking the back side of the hole location on the back side of the post/timber, then all holes are through holes bored through from the layout face.

If the bit hits some internal defect, like a knot, and wanders off line after passing through the mortise then it really doesn't matter. But from the layout face threw the mortise should be right on the mark.

A lot of this will depend on the type of pegs you're using.
If you are buying turned pegs or pegs that look like dowels then you could do a blind peg hole. But if you are shaping your own pegs using a shaving horse and a draw knife then you should allow enough room for the taper point to pass beyond the back side of the mortise at least 2" or more. This will allow more holding wood to hold the peg and tenon in the mortise.

On our frame here we are using 10" long pegs to go through 6x6 timbers, with through holes at every mortise.
It is very easy to push a peg out of a through hole, then to pull one from a blind hole, in case you need to take your frame down.

When we raise our frame here, in a few weeks, we will not be driving the pegs all the way in, because this frame is still "for sale" and will be disassembled and moved to the customer's site, once sold. We will drive the pegs in enough to hold the frame together and for it to be safe.

Thanks for the question, it was a good question and that's why I posted it with the answer.

I'm looking forward to seeing your finished frame pictures....

Jim Rogers
Whatever you do, have fun doing it!
Woodmizer 1994 LT30HDG24 with 6' Bed Extension

beetle

Thank you again. On the posts that I have completed I bored blind mortises and left the approx. 1" of stock between them, ( I was not sure and felt I could always take it out later but I can't put it back). I plan on using hand carved pegs, going to wait and bore my peg holes when it is time to assemble so they do not egg shape on me.

So far I have connected to no electricity or poured any gasoline, different from what I have done in the past and I aint covered with dust and smelling fumes...kinda nice.

Have fun.
Too many hobbies...not enough time.

beetle

So far I have cut 24  brace pockets on my posts. I am using the 2 / 2 method off the layout face with 1/2" housings.

A couple of my housings I have accidentally got a little deep, about a 1/16" to a 1/8" at the most. What problems is this going to cause at time of assembly and raising ? If it will cause trouble, any suggestions on how to correct them?
Too many hobbies...not enough time.

Jim_Rogers

Jeff/Beetle:

I had planned on doing a story about how to cut a brace pocket as it was missing from the above story.

I'm sorry I haven't gotten to that yet.

As to your questions about the depth of your pockets. If the actual pocket where the tenon goes is too deep that isn't a problem and you shouldn't have to worry about that. As long as the bearing end of the pocket is cut correctly, as well as the bearing end of the tenon on the brace. These location have to be exact.

But if you're referring to the housing area where the shoulder of the brace rests on, it's important that this be correct as a good part of the bearing is at this shoulder as well as at the bearing end.

You'll need to cut a shim and put it in/on the housing to bring it back up to the correct place.

If you don't it won't work as well as it could and it won't look very good.


The procedure for cutting a brace pocket is to lay it out, knife the lines around the pocket and then cut out the pocket. Using a boring machine or a drill you hog out the waste wood and then "pare" to the knife line to the size of the pocket opening.
After all this is done to the correct depth. You then cut the housing at the edge of the pocket, where the shoulder of the brace will sit. Basically housing is cut last.
Once the housing is cut you then locate your peg hole.

I'll do a step by step photo shoot of this sometime and will write up a story about it.

Good luck with your project.

Jim Rogers
Whatever you do, have fun doing it!
Woodmizer 1994 LT30HDG24 with 6' Bed Extension

beetle

Thanks Jim,

Yep it is the 1/2" housing depth that I am referring to. On a couple of them the chisel caught the grain and I am somewhere around 9/16 deep. Going to have to be a little more carefull.

I have been cutting just as you described above...Mark, score, bore, and chisel the mortise, then I cut down the housing depth 1/2" line with a crosscut saw then chisel to the paralel line. I just caught the grain on a couple and ended up a little deeper than 1/2". Guess I will have to shim.
Too many hobbies...not enough time.

Jim_Rogers

Jeff/Beetle:

You need to score the housing line on the side of the timber, the side the peg hole is laid out on. This will help you to not over cut it.

When I say we score "all" lines that means all the lines we will cut to, even housing lines. And housing lines can travel around corners onto other faces, sometimes.

We even score lines that will be cut off later, so that we can use the scored line first.

Keep an eye on your lines.

Jim Rogers

Whatever you do, have fun doing it!
Woodmizer 1994 LT30HDG24 with 6' Bed Extension

beetle

Jim,

That statement got me thinking about some good old memories.... my Dad teaching me how to drive that old 69 Ford truck with a three on the column. He kept telling me " keep a eye on the line son "

Thanks.....
Too many hobbies...not enough time.

beetle

Jim,

If I identify the ones that I have overcut, can I correct them by increasing the 3/8" offset line slightly and fitting each brace to the those housings? If I do not screw anymore up, I should only have two or three that would need custom fitting, therefore, eliminating the need to shim.
Too many hobbies...not enough time.

Jim_Rogers

Jeff/Beetle:
Yes, but the new special one will have to be properly labeled (some place where it won't show), that these are special ones to be used in only that special location.
It should work if you increase the 3/8" line to the actual surface, but I've never tried it so, when I say it should work that's in theory.
Let us know how you make out.
Jim Rogers
Whatever you do, have fun doing it!
Woodmizer 1994 LT30HDG24 with 6' Bed Extension

beetle

Hello everyone, hope you all had good holidays.

Since I cannot get much done outside this time of year, I have been cutting all my braces and girts inside my shop.

I estimate that I will raise my barn around July/August 2005, if I drill the peg holes in the braces and Girts now are they going to "egg shape " on me while stored this lenght of time ? 6-7 months. All of the other timbers I have cut I have not drilled the holes since some of them will have been cut for a year.


Still chipping in Ohio
Too many hobbies...not enough time.

Jim_Rogers

Drilling holes now, may not be the best method.
First of all the holes could distort and change shape and end up egg shaped, as you say.
But also, you holes may not be in the right place, on the tenon.
I tried to say and show before that you should bore your holes at the time of your full scale fit up. If you bore the mortise holes dead on the spot or mark then they will be ok. Then if you're using a draw bore you should offset your holes on the tenon, as needed to create the draw bore. This is done by placing the tenon in the mortise and running the bit down the mortise peg hole and prick the tenon to indicate the exact hole location center, then offset from there.
If during your full scale fit up you see that your frame is not coming together right, as dimensions don't measure out right then you may need to shave a shoulder or two to adjust the fit. This could move the hole location some and therefore through out the draw bore or correct hole location.
I'd wait and bore all holes later.
Jim Rogers
Whatever you do, have fun doing it!
Woodmizer 1994 LT30HDG24 with 6' Bed Extension

beetle

Good point about trimming and or adjusting may throw the tenon hole out of tolerance. I will wait and drill upon fit up.

Thank you for the good advise.

Jeff
Too many hobbies...not enough time.

Jim_Rogers

Read the new posts about procedures.......

And keep asking questions.......
Whatever you do, have fun doing it!
Woodmizer 1994 LT30HDG24 with 6' Bed Extension

Tony_T

Hi Jim,

Was just soaking in your guidance on laying out/cutting braces by square rule, thanks!

Stubborn me have been teaching myself layout by scribe rule method and think I've got it figured out how to layout braces using compass, chaulkline, plumbbob, etc. 

I can get diagonal lenghts by laying out a reference triangle based on the depth of the "true" brace using the compass.  Setting the compass to the reference triangle you can walk out turns for diagonal lenghts and for positioning the pockets to layout the mortises on the beams; no "math" involved (e.g. A2 + B2 = C2). Unlike using the sqaure rule above I assume the brace is oversize and end up with a slightly oversize brace except on the ends that have been trued for the tennon and to fit the pocket.  That is the brace fits well but may not be flush with the beam where it meets the pocket.

Took me two days on paper to figure how to get diagonal lenghts without a ruler and calculations., that is only using the compass for measurements.  Do you know of any reference books for layout by scribe rule?  Will start playing with rafter layouts next........

Jim_Rogers

Tony_T:
I don't know of any books that talk about laying out for scribe rule.
I thought you'd lay one timber over the other and transfer locations by using a plumb bob line.
This would tell you where the mortise should be and also the tenon.
I don't personally have any experience in scribing but the magazine "Timber Framing" just had an article about it.
If you're not a member of the guild you could buy one copy of this magazine to read that article.
I can let you know the publication number if you need/want it.
Jim Rogers
Whatever you do, have fun doing it!
Woodmizer 1994 LT30HDG24 with 6' Bed Extension

hayton1960

I read tfg magazine 34, 35 and 36, Marc Guilhemjouans 3 part "introduction to French scribe", which is very useful, only it just sort of ends abruptly and leaves you in mid air not knowing where to go next just when it starts to get real interesting. PS does anybody know what is going on with his new site; the forum is like a ghost town, as far as I can tell I'm the only person who posted anything (except the site manager)! Do I have a fault with my computer?
Cheers Jonathan

Jim_Rogers

What site are you talking about?
Post a link for me to look at it.

Jim Rogers
Whatever you do, have fun doing it!
Woodmizer 1994 LT30HDG24 with 6' Bed Extension

hayton1960

Hi Jim
The site is a newer version of his old one

www.traditionaltimberframe.com

As far as I can see he has dropped the excellent animated diagrams of how to set out hexagons/septagons/nonagons etc using compasses
I hope this link works OK!

Tony_T

Quote from: hayton1960 on October 26, 2005, 03:14:16 PM
Hi Jim
The site is a newer version of his old one

www.traditionaltimberframe.com

As far as I can see he has dropped the excellent animated diagrams of how to set out hexagons/septagons/nonagons etc using compasses
I hope this link works OK!

Jonathan, the animated diagrams are still there:

http://www.traditionaltimberframe.com/ttfv2/index.php?mod=page&ac=page&id_page=4

It's an interesting site but more geometry layout using a compass than actual applications to framing.  It would be nice if there were some animated diagrams of actually laying out framing pieces.  Though I have used some of the things I learned on that site for layout using my compass.

I'll check out the references 34-36 in tfg.  I'm not a member (yet) so not quite sure how I can locate these?  Are they available online?

hayton1960

Hello Tony mate
I never had to become a member to get the back issues, I just e-mailed a Mrs Michele Beemer and I got it in the mail soon after. Maybe it is available on a download-I dont know
As I understand it, the traditional French way of setting out relies on using the compass to set out horizontal/vertical/any and all angles for roof pitches etc for the full scale drawing on the floor. Like with decorating or cooking-good preperation is the main part of the job. I think that is why its featured so much on the site. But your right, the actual picage stage where you relate your full scale drawing to your timber and then  mark your mortise positions and tenon shoulders etc, is non existant, in the website and in the tfg articles (I'd still definately recomend those articles though) Maybe you gotta go to one of Marcs courses to proceed further with it?
Cheers Jonathan

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