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Author Topic: 300 yr old RI timber frame Colonial in need of ideas to increase floor strength  (Read 658 times)

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Offline Reiniken

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Hi everyone. I知 sure you will see that this is my 1st post, so I値l apologize in advance to anyone my post may offend or frustrate. I have a long, long list of work that I will be doing to my house in 2020 and I was hoping the community might have some advice on one particular part of my plan.

A little background info on the house: 2-story colonial, 27.5 x 36 timber frame built in 1720, enclosed with very wide 6/4 vertical plank sheathing on walls and roof, gunstock posts, two summer beams, 8x6 central chimney, 8x6 rafters spaced 8 apart, granite stone foundation, timbers marked with Roman numerals, etc etc. The majority of the house is now fully exposed down to the exterior vertical plank sheathing & beams exposed on the interior, which haven稚 been seen by anyone else in a very long time.


 

 

I believe the floor joists are oak (pic shown below), although I could be wrong. They measure true 3 x 4.5-5, all stretching 11-ft throughout, with the exception of the joists at the summer beams, which are 7-ft in length. All joists are randomly spaced 18-22 apart. All joists are fully seated into the beams, meaning the ends are not notched. The beams have full pockets 2.5 deep, 3 wide, 4.5-5 high. Every other joist is cut like a half-dovetail. I知 sure there痴 a specific name for it, I just don稚 know it.


 

 



 

Since it is 2020 and my family will be living in the house, I need to be sure the flooring structure can handle the dead load of our modern household furniture, beds, bathrooms, appliances, etc. (claw foot tub & soap sinks are gone!). Also, since I don稚 have unlimited time, or unlimited money, I have to make the best of the situation with what resources I have. The foundation is in remarkably good condition, as is the sill, although some sections of the sill will be properly repaired/replaced.

My plan is to leave the existing joists as-is, since they are quite straight for their age, and, in between each old joist, attach (2) 2x6 Douglas Fir #1 joists to the beams by use of a Simpson joist hanger/10d nails driven into the beam. The old joists will be shimmed underneath for a new ceiling below. セ sheathing will then be installed on top of the joists. I have attached a sketch of my idea below. If anyone has any input as to whether or not I am absolutely crazy, or if this might be acceptable, I would greatly appreciate it. The floors won't support anything crazier than a typical modern house would have (fiberglass bathtubs, kitchen counters & appliances, bathroom vanities, couch, dining table/chairs, etc.



Thank you for your time. Also, given the age and uniqueness of my timber frame, if any other pictures of my frame might be useful to the community to post online, let me know (I have many).  Thanks again everyone.

Offline A-z farmer

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Re: 300 yr old timber frame Colonial in need of floor support
« Reply #1 on: February 13, 2020, 08:51:18 PM »
Reiniken
Welcome to the forestry forum .I do not have any answers to your question but there are lots of knowledgeable people here who do.It took me a year of trying here to be able to post pictures so you have done great .

Offline Mike W

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Sure that would stiffen the floor, based on your diagram that would put floor joists every 9 to 11" o.c. I would be more concerned with the added dead load to what appears to be an already taxed 8x8 spanning 16' unsupported with a significant amount of material removed from the 8x8 with those full seat notches.  Any way or can you live with adding a post to cut that span in 1/2?  also I would install additional joists to get to a standard layout such as 16" o.c. to simplify the subfloor installation rather then focusing on centering the new joists as shown, even if it was to sister a joist against the existing to get to a standard layout it would still help significantly to stiffen the floor.  

there is a really cool span calculator on this forum, its in the toolbox on the left side of the page at the bottom, check that out and run some #'s on that 8x8 for loading to see what type of deflection you are dealing with on that beam.

good luck with the renovation, historical work like that is always fun to do

welcome to the FF 

Offline Don P

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Is this the main or second floor? Can you post pictures of both floor systems and support members?
From the sounds of the spans the 8x8 girders and the joists are overspanned, stiffening the joists and adding more with finishes increases dead load and we live much heavier than our ancestors. Typically a 2x6 spans out around 8', engineered wood may be better but that doesn't fix the girder and is probably not deep enough. Can you add more supports? Can you accept more floor depth? I'm also wondering if there is a way to accomplish this without harming the fabric of what is there in case someone wants to do a restoration later.

I se mine didn't post this morn on the way out, some is redundant of Mike's but a few more questions.
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Offline scsmith42

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That siding appears to have been band sawn.  If it was period, it would have been pit sawn with variances in the saw kerf marks.
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Offline Tom King

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You've gotten good advice here, so far.

The only thing I have to add, right now, is that if it was built in 1720, chances approach zero that the foundation stone is Granite.  Sandstone comes in Many variations.  Some of it can even be more dense than Granite.  I forget when they first started quarrying Granite, but I think it was sometime around 1840's.

Offline Reiniken

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Sure that would stiffen the floor, based on your diagram that would put floor joists every 9 to 11" o.c. I would be more concerned with the added dead load to what appears to be an already taxed 8x8 spanning 16' unsupported with a significant amount of material removed from the 8x8 with those full seat notches.  Any way or can you live with adding a post to cut that span in 1/2?  also I would install additional joists to get to a standard layout such as 16" o.c. to simplify the subfloor installation rather then focusing on centering the new joists as shown, even if it was to sister a joist against the existing to get to a standard layout it would still help significantly to stiffen the floor.  

there is a really cool span calculator on this forum, its in the toolbox on the left side of the page at the bottom, check that out and run some #'s on that 8x8 for loading to see what type of deflection you are dealing with on that beam.

good luck with the renovation, historical work like that is always fun to do

welcome to the FF
Hi Mike, thanks for taking the time to respond. I didn't going into detail about much else in my original post because I thought it was too long. I agree that there is a significant amount of material removed from the 8x8, however it is straight as an arrow and level. This beam in the picture supports the attic floor. Directly below that 8x8 beam is a wall of wide plank boards, just like the exterior sheathing (2"x18"x87"). They literally can be pushed out with two fingers, as if there is no load on them. Directly below that 8x8 beam and wall boards is an 8x10 beam, same 16' length. Just like the 2nd floor, there is a wall of wide plank boards. Just like the 2nd floor, you can literally push them out with two fingers. There is a door opening on each end of the 16' run on the 1st floor, and one door opening on the 2nd floor 16' run. The 1st floor wall boards are supported by a 10x10 beam in the basement that is also 16' long. Underneath that 10x10x16 are two lally columns supported by a concrete floor.


 


 


 


 


 
I did not mention in the original post that part of my plan is to replace all of the wall boards on the 1st floor with a single 8x8 post and the same with the other 8x8x16 beam that runs perpendicular to form the 16x16 room. To attached them, I planned on using T-Rex adapters (T-REX - Timber Frame HQ). The inventor/owner lives within driving distance. I would prefer to use a traditional method, however money & time are the deciding factor.

Thank you for suggesting the calculator. It's kind of funny, because I have been looking at calculators online for a while and that is really what prompted me to reach out to the forum. None of the spans and sizes work when using the calculators. So it got to a point where I was like, do I trust the calculators or 300 years of physical proof? I really don't want to mess with what has been working for centuries, even if all the calculators don't agree. The existing joists are spaced 18-22" (varies), so achieving 16" o.c. doesn't seem possible if I leave the existing joists as-is. That was why I initially thought of adding the 2x's to what already is working. I just wasn't sure if my idea was practical, or totally nuts.

Offline Reiniken

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Is this the main or second floor? Can you post pictures of both floor systems and support members?
From the sounds of the spans the 8x8 girders and the joists are overspanned, stiffening the joists and adding more with finishes increases dead load and we live much heavier than our ancestors. Typically a 2x6 spans out around 8', engineered wood may be better but that doesn't fix the girder and is probably not deep enough. Can you add more supports? Can you accept more floor depth? I'm also wondering if there is a way to accomplish this without harming the fabric of what is there in case someone wants to do a restoration later.

I se mine didn't post this morn on the way out, some is redundant of Mike's but a few more questions.
Is this the main or second floor? Can you post pictures of both floor systems and support members?
From the sounds of the spans the 8x8 girders and the joists are overspanned, stiffening the joists and adding more with finishes increases dead load and we live much heavier than our ancestors. Typically a 2x6 spans out around 8', engineered wood may be better but that doesn't fix the girder and is probably not deep enough. Can you add more supports? Can you accept more floor depth? I'm also wondering if there is a way to accomplish this without harming the fabric of what is there in case someone wants to do a restoration later.

I se mine didn't post this morn on the way out, some is redundant of Mike's but a few more questions.

Hi Don, thanks for taking the time to respond. Yes, I agree that everything is over-spanned and undersized. The house has been occupied by large families right up until I bought it and is documented back to 1720 (it's in the National Historic Register). I can guarantee that I've easily exceeded the dead load limits of the sized joists based on all calculators I come across online. During an addition in 1898, a post was literally cut off to make a room/ceiling larger. This means that the 2nd story girder on the East side of the house has been fully suspended over a span of 28', only held together by the joint with a 2nd story post, which is also directly under a rafter. So for the past 102 years, a 28' unsupported span has supported two bedrooms, a bathroom with a claw-foot tub and under load from two rafters, without any support other than the vertical plank sheathing and plaster/lath. I had the house inspected in 2018 by the now Executive Director of the Timber Framers Guild while he was an engineer at Fire Tower Engineered Timber and he said the house was solid as a rock. Obviously, he said 2-3 posts should be added for support under that span, but wasn't overly concerned because it last for 102 years and survived a direct hit by two large pine trees four weeks prior to the inspection (hence why everything is now exposed). Everything is way over spanned and undersized, but together, it somehow all works. The solid black squares in the pic below represent the rafters.


 


 


 
To help offset the added weight of additional supports, I've removed about 2,000 sqft of horsehair plaster. The previous floor system had 1/2" plank subfloor and 1.25" wide pumpkin pine floor boards in 16' lengths. My plan is to install a 4'x8' 3/4" subfloor with 3/4"x12"x16' pine on top. I also planned to add an equally sized post to the middle of all horizontal timbers on the 1st & 2nd stories and attach them with T-Rex adapters (T-REX - Timber Frame HQ).
As far as the floor depth, I'm considering 2x8's instead of 2x6's for the added supports. I'm also considering the 2x that my wife might whack me with when she notices the lower ceiling height! Here's a sketch up of the flooring systems for each story. All beams on the interior are currently supported by 2x15-18" wall boards and will be replaced by an 8x8 mid-span at the same location on each story.


 


 
I realize its kind of difficult to visualize my description, so I made this (see below). The red represents the post, and two other beams, that were completely cut out, with only stubs left.



Offline Reiniken

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That siding appears to have been band sawn.  If it was period, it would have been pit sawn with variances in the saw kerf marks.
Hi scsmith42, thanks for responding.
Here in colonial New England, water powered saw mills were commonly used from the mid-1600's on. A little back story on the house. It's on the National Historic Register (the builder's sister was one of the afflicted girls in the Salem Witch Trials, sister is known as the girl who taught Tituba to make "witch cakes", daughter/family was portrayed in the "Salem" HBO series, family is acknowledged in the Salem Witch Museum, the father of the builder was a Capt. in the Salem Militia and friends with Roger Williams, family was banished from Salem after the trial/hangings, the builder's son fought in the Revolutionary War & his uniform was pulled out from under the floor boards). Interestingly, and somewhat creepy, the wide plank interior wall boards have "W" written all over some, as well as drawings depicting women in dresses shaped like an Aunt Jemima bottle with creepy characters on each side with dark heads and arms stretched out. These boards haven't been visible for well over a century, if not two.
The builder was the owner of a water-powered sawmill, located approx. 150 yards from the house, that pre-dated the house. When he built the house in 1720, the 32 acres were actually part of the Massachusetts Bay Colony. In 1745, he built a second nearly identical house about 100 yards from my house (my neighbors are sleeping in it right now). In 1746, Massachusetts Bay Colony sold the land to Rhode Island and the town of Cumberland was formed. The builder of the house became one of the first four town council members. In the Town Hall, my house, and my neighbor's house, appear on page 1 of the original land record book as residences pre-dating the town. I was also shown a map of the town, dated 1870, that has my house marked with the family's name & "1720". I have had local historians and the historical society verify it is first period construction. I was also informed that the oldest house in Rhode Island (1691) confirmed by dendrochronology consists of all water mill-sawn timbers.
If this house were built anywhere else other than Colonial New England, or Jamestown, I'd totally agree with the pit sawn theory.

Offline Reiniken

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You've gotten good advice here, so far.

The only thing I have to add, right now, is that if it was built in 1720, chances approach zero that the foundation stone is Granite.  Sandstone comes in Many variations.  Some of it can even be more dense than Granite.  I forget when they first started quarrying Granite, but I think it was sometime around 1840's.
Hi Tom, thanks for taking the time to respond.
While there is sandstone mixed throughout (different color variations, some pinkish, some tan, some like marble), much of it is gray granite. I probably should have been clearer in my original post. I was just trying to give some info for viewers to visualize a typical first period colonial Massachusetts house. My stairs that go from the basement to the 1st floor are massive granite rocks approx. 50" wide, 8" high and 9" deep. They aren't cut. The center of the basement has a large granite stone foundation with limewash that supports the 6'x9' central chimney, as well as supports the central interior beams/posts. The perimeter foundation (28x36) is a mixture of sandstone and granite with limewash. They aren't giant granite stones like the Pyramid of Giza. They are approx. 8-18" high, 2-4' in length, various shapes, not square or cut. There is 7' height clearance in the basement. I have personally visited several period homes that have large, central chimneys in RI & MA with a similar foundation. I'll try to get some clear shots when I'm over there next week.

Offline Don P

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What a cool house!
Of the group here Tom is the old house guru, I'm just throwing some thoughts out.
I'm guessing the sawmill was a sash saw? My far less than perfect understanding was that the colonies were prohibited from having water powered mills to avoid industrial competition with the motherland. They were at the time envisioned as a resource to be exploited rather than a competing power. I'd sure like a better education there though.

It looks like the removed post was in the exterior wall, if I'm seeing that all correctly that is less concerning, the wall itself has become a uniform load path for that beam, it really isn't spanning but is uniformly supported.

Calcs use "allowable" design values for strength and stiffness and are based on the lower 5th percentile of sampling of the current timber resource. You just saw two big variables as compared to your timbers. The small sections in your pics appear to be high grade and the resource has changed from what was originally available. On my mill I often see that I'm well above the middle of that bell curve yet am sizing based on the lower tail. I'd be comfortable with the onsite engineers assessment. I'd also retain them for this remodel.

Although your plank walls appear to be unloaded, the building is unloaded, be careful with that assumption. Assuming those are good... To get more joist stiffness and strength I'd try very hard to go up to 7-1/4" joist depth. If you can take the depth out of the 2nd floor I'd put a ~2" plate on top of the girders and use top mount hangers fastened to that "shim", avoiding face mounting to the originals. The joists could be TJI's which are stiffer and lighter than solid sawn. The existing joists could then be shimmed to flat. You could also split the depth difference using a 1" shim above and 1" below. This would limit your holes to edges that have already seen nails.

One thing I've been cautioned about with horsehair plaster is it often came from the local tannery that may have used some pretty harsh chemicals to help remove the hair, arsenic being one. This may predate that but be very self aware working on old buildings, there may have been some pretty bad things in their history. Suit up and clean up well.
A laborer works with his hands
A craftsman uses his brain and his hands
An artist uses his brain, his hands, and his heart

Offline Reiniken

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What a cool house!
Of the group here Tom is the old house guru, I'm just throwing some thoughts out.
I'm guessing the sawmill was a sash saw? My far less than perfect understanding was that the colonies were prohibited from having water powered mills to avoid industrial competition with the motherland. They were at the time envisioned as a resource to be exploited rather than a competing power. I'd sure like a better education there though.

It looks like the removed post was in the exterior wall, if I'm seeing that all correctly that is less concerning, the wall itself has become a uniform load path for that beam, it really isn't spanning but is uniformly supported.

Calcs use "allowable" design values for strength and stiffness and are based on the lower 5th percentile of sampling of the current timber resource. You just saw two big variables as compared to your timbers. The small sections in your pics appear to be high grade and the resource has changed from what was originally available. On my mill I often see that I'm well above the middle of that bell curve yet am sizing based on the lower tail. I'd be comfortable with the onsite engineers assessment. I'd also retain them for this remodel.

Although your plank walls appear to be unloaded, the building is unloaded, be careful with that assumption. Assuming those are good... To get more joist stiffness and strength I'd try very hard to go up to 7-1/4" joist depth. If you can take the depth out of the 2nd floor I'd put a ~2" plate on top of the girders and use top mount hangers fastened to that "shim", avoiding face mounting to the originals. The joists could be TJI's which are stiffer and lighter than solid sawn. The existing joists could then be shimmed to flat. You could also split the depth difference using a 1" shim above and 1" below. This would limit your holes to edges that have already seen nails.

One thing I've been cautioned about with horsehair plaster is it often came from the local tannery that may have used some pretty harsh chemicals to help remove the hair, arsenic being one. This may predate that but be very self aware working on old buildings, there may have been some pretty bad things in their history. Suit up and clean up well.
Hi Don! Thanks for all of the info and suggestions. I really do appreciate it. I feel relieved about that missing exterior post not being as big a deal as I was thinking. I think your idea of adding the top plate on top of the girders is spot on with my plan "B", which will now become "A". I had initially thought of going with a full 2x8 so the bottom of the joists would be somewhat level with the bottom of the existing joists, without changing the ceiling height of the 1st floor. I would lose 2-3" on the 2nd floor, but that is ok, because the ceiling height of the 2nd floor was 2" higher already. The two main reasons I didn't make that my plan "A" was because I wasn't sure what nail length would be best to attach the 2" plate to the girders, or if it would compromise the strength of the girder. A timber contractor had thrown out the idea of sistering every joist with full length 2x8's/lag bolts (after adding mid-span supports) to create a level surface for the ceiling/subfloor, and then support them with custom steel top mounted joist hangers to accommodate the new joist width. I thought it might be a sort-of good idea, but I really wasn't comfortable with the number of bolts and size of bolts that would go into the girders. I'm much more comfortable with your idea. Thank you very much for your input, I really do appreciate it.
As far as the plaster, I cut out a 4"x4" section and had it tested first. It was chemical free. I found there was two different types of plaster, one on top of riven lath and one on lath with circular saw marks. The plaster on the circular saw lath was thick, 5/8's or thicker. Walls that had this plaster took about 15 minutes to clear the entire wall of approx. 80 sqft. of plaster. On the walls that had riven lath, the plaster was much thinner, 3/8's at best, yet was like 10x harder/stronger. It took 10 minutes to clear about 1 sqft. I used everything from the typical plaster scraper (which was totally useless on this plaster but great on the other plaster), to anything that would provide blunt force (hammers, sledge hammer, dull axe, pry bar and anything else available). The only way to clear it was prying the ends of lath up and pulling 3-4 strips by hand at a time, and the plaster still barely came off the lath! Clearly whatever they used was far superior to anything that came afterwards. The riven lath was about 3/8's or thicker, compared to a 1/4" for the circular saw lath. I'm not sure what to do with the miles of lath I have, but the unpainted lath looks like it would make nice America flags for the 4th of July to stick in the ground or hand on a wall when I rotate sides (see below). Obviously I'd have to cut them down to the proper dimensions and add a little translucent blue, but I could probably make about 500 of these!


 
It also made the beginning of a cool lemonade stand for my toddlers (obviously not finished).


 
Thanks again Don!

Offline Reiniken

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What a cool house!
Of the group here Tom is the old house guru, I'm just throwing some thoughts out.
I'm guessing the sawmill was a sash saw? My far less than perfect understanding was that the colonies were prohibited from having water powered mills to avoid industrial competition with the motherland. They were at the time envisioned as a resource to be exploited rather than a competing power. I'd sure like a better education there though.

It looks like the removed post was in the exterior wall, if I'm seeing that all correctly that is less concerning, the wall itself has become a uniform load path for that beam, it really isn't spanning but is uniformly supported.

Calcs use "allowable" design values for strength and stiffness and are based on the lower 5th percentile of sampling of the current timber resource. You just saw two big variables as compared to your timbers. The small sections in your pics appear to be high grade and the resource has changed from what was originally available. On my mill I often see that I'm well above the middle of that bell curve yet am sizing based on the lower tail. I'd be comfortable with the onsite engineers assessment. I'd also retain them for this remodel.

Although your plank walls appear to be unloaded, the building is unloaded, be careful with that assumption. Assuming those are good... To get more joist stiffness and strength I'd try very hard to go up to 7-1/4" joist depth. If you can take the depth out of the 2nd floor I'd put a ~2" plate on top of the girders and use top mount hangers fastened to that "shim", avoiding face mounting to the originals. The joists could be TJI's which are stiffer and lighter than solid sawn. The existing joists could then be shimmed to flat. You could also split the depth difference using a 1" shim above and 1" below. This would limit your holes to edges that have already seen nails.

One thing I've been cautioned about with horsehair plaster is it often came from the local tannery that may have used some pretty harsh chemicals to help remove the hair, arsenic being one. This may predate that but be very self aware working on old buildings, there may have been some pretty bad things in their history. Suit up and clean up well.
Hi Don! Thanks for all of the info and suggestions. I really do appreciate it. I feel relieved about that missing exterior post not being as big a deal as I was thinking. I think your idea of adding the top plate on top of the girders is spot on with my plan "B", which will now become "A". I had initially thought of going with a full 2x8 so the bottom of the joists would be somewhat level with the bottom of the existing joists, without changing the ceiling height of the 1st floor. I would lose 2-3" on the 2nd floor, but that is ok, because the ceiling height of the 2nd floor was 2" higher already. The two main reasons I didn't make that my plan "A" was because I wasn't sure what nail length would be best to attach the 2" plate to the girders, or if it would compromise the strength of the girder. A timber contractor had thrown out the idea of sistering every joist with full length 2x8's/lag bolts (after adding mid-span supports) to create a level surface for the ceiling/subfloor, and then support them with custom steel top mounted joist hangers to accommodate the new joist width. I thought it might be a sort-of good idea, but I really wasn't comfortable with the number of bolts and size of bolts that would go into the girders. I'm much more comfortable with your idea. Thank you very much for your input, I really do appreciate it.
As far as the plaster, I cut out a 4"x4" section and had it tested first. It was chemical free. I found there was two different types of plaster, one on top of riven lath and one on lath with circular saw marks. The plaster on the circular saw lath was thick, 5/8's or thicker. Walls that had this plaster took about 15 minutes to clear the entire wall of approx. 80 sqft. of plaster. On the walls that had riven lath, the plaster was much thinner, 3/8's at best, yet was like 10x harder/stronger. It took 10 minutes to clear about 1 sqft. I used everything from the typical plaster scraper (which was totally useless on this plaster but great on the other plaster), to anything that would provide blunt force (hammers, sledge hammer, dull axe, pry bar and anything else available). The only way to clear it was prying the ends of lath up and pulling 3-4 strips by hand at a time, and the plaster still barely came off the lath! Clearly whatever they used was far superior to anything that came afterwards. The riven lath was about 3/8's or thicker, compared to a 1/4" for the circular saw lath. I'm not sure what to do with the miles of lath I have, but the unpainted lath looks like it would make nice America flags for the 4th of July to stick in the ground or hand on a wall when I rotate sides (see below). Obviously I'd have to cut them down to the proper dimensions and add a little translucent blue, but I could probably make about 500 of these!

(Image hidden from quote, click to view.)
 
It also made the beginning of a cool lemonade stand for my toddlers (obviously not finished).

(Image hidden from quote, click to view.)
 
 
(Image hidden from quote, click to view.)
 
Thanks again Don!

Offline Reiniken

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I threw this mock-up together today. It's a 1:12 scale. The red indicates what was cut out in 1898 and is completely missing right now. The rafter ends are birdsmouth, not crowsfoot, and as expected are split on the ends.


 

 

 

 

 

 

 

 

 

Offline Don P

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You were busy! I don't know why but that sure makes it easier to visualize.
I forgot to ask, what does the yellow indicate in your drawings above?

Looking at the split rafter ends, are any running up through the piece getting ready to break it? One possible repair is to run structural screws from the bottom up. Usually a prebore in the lower half so it is just free of the screw and dead into the upper half.
That rafter detail is one that should be dropped to the wayside by builders going forward.

There are a number of very good timberframers in your area. With the frame open and with the historical significance of this house you might want to consider inviting the Guild over to have a TTRAG tour and brainstorm session.
A laborer works with his hands
A craftsman uses his brain and his hands
An artist uses his brain, his hands, and his heart

Offline Nebraska

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That is so amazing. If it could speak...

Offline Don P

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That is so amazing. If it could speak...
It would say "She turned me into a newt"
A laborer works with his hands
A craftsman uses his brain and his hands
An artist uses his brain, his hands, and his heart

Offline florida

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Fascinating house and topic! I wish I had anything intelligent to say. YT has fed me videos from this German guy who repairs old timber frames like yours. Some of what he does surprises me but I assume he knows what he's doing.

Matthias Burger - YouTube
General contractor and carpenter for 50 years.

Offline Reiniken

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You were busy! I don't know why but that sure makes it easier to visualize.
I forgot to ask, what does the yellow indicate in your drawings above?

Looking at the split rafter ends, are any running up through the piece getting ready to break it? One possible repair is to run structural screws from the bottom up. Usually a prebore in the lower half so it is just free of the screw and dead into the upper half.
That rafter detail is one that should be dropped to the wayside by builders going forward.

There are a number of very good timberframers in your area. With the frame open and with the historical significance of this house you might want to consider inviting the Guild over to have a TTRAG tour and brainstorm session.
Hi Don, glad the mock-up made things easier to visualize. The "yellow" areas on the computer-drawn image represented areas where I had expected to find rot/insect damage with the sill & sill/post joints, however it was much better than expected.
Here is a picture of one rafter with the split end. The heel on the inside of the top plate is just resting against the beam, as I can drawn a continues line downward between the split without any break in the line. I imagine the rafter seat is notched into the top plate to a specific depth, which I haven't had the chance to inspect yet. This particular rafter in the picture took a direct hit from a large Pine tree that fell onto it during the back-to-back-to-back Nor'Easter storms in March 2018. It shattered the horizontal purlins on each side of the rafter, as well as the vertical wide-plank decking spanning two rafters. I added a picture below with the area circled. The sprocket that is notched into the top plate next to the rafter was also shattered. Surprisingly, the 8x6 rafter appears to have held its own, even with the split end. The adjoining rafter to the other side of the house appears to have failed. Fire Tower Engineered Timber indicated that the tree fell in the opposite direction of the wind on the blow-back and the excessive wind possibly could have caused the other rafter to fail, however there is no way to know for sure.


 


 
Given the split rafter ends, at least one failed rafter, damaged decking and purlins, my plan was to replace all rafters and cut new rafters of the same size (8x6), double the number of rafters to reduce the span from 8' to 4', add pegged collar beams and a proper ridge beam for additional support. I figured I would cut the rafter ends to match the existing seats. The new rafters would have identical ends cut and seats notched in the top plate. Directly underneath each new rafter end at the top plate would be an 8x6 vertical support added on each floor down to the sill. Obviously, I'll consult with Fire Tower first, but that would be the plan.

Offline Don P

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That "split" appears to just be a vertical seasoning check and doesn't really affect the rafter strength if I'm seeing things correctly. The split that would concern me is one that runs out of the re-entrant corner, especially if it is running out of the rafter like this one;





 What is the reason why you are contemplating replacing the rafters?

A laborer works with his hands
A craftsman uses his brain and his hands
An artist uses his brain, his hands, and his heart


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