Notice to all readers: I am not a structural engineer. The statements made below is based on extensive research online and not made by an engineer professional. I am an architect with some basic understanding of structural engineering. Do not make design decisions based on this post without first doing your own research and speaking with an engineer.
With that being said, let's talk about collar ties.
The above picture shows one of the "collar ties" that was original to the construction of our home. These were installed every 4 or so rafters. My original intention was to keep these and wrap them in trim but i decided to remove them. Here is why.
First off, let me clarify what collar ties are exactly. Sometimes engineers design collar ties to prevent separation of the roof at the ridge due to wind uplift. Collar ties should only be required when there are no ceiling joists or structural ridge beam to serve the function. When collar ties are properly designed to resist wind uplift, the engineer usually will specify through bolts and spike grids anchored to the roof rafters. The hardware is required in order to properly connect the collar tie to the rafter; a few nails, as was the case in our house, won't do the job. Plus the "collar ties" were 2x4's. In order for it to be substantial to function as a true collar tie it would need to be a much larger member.
Most of the codebooks and construction textbooks today dont require collar ties or show them in details anymore. However, building codes do require that the rafters themselves 1.) need to be properly sized to accommodate roof load requirements and 2.) that the ceiling joists be fastened at lap joints to resist outward thrust from the weight of the roof.
If the design of roof framing does not allow for the roof rafters to be connected to ceiling joists, then collar ties and/or rafter ties would be required to resist the forces caused by gravity loads that otherwise cause the roof to pancake and push the exterior walls outwards. Rafter ties are required by code, unless the engineer designed the house so that there is a ridge beam that carries the load of the roof.
The sketch above shows the condition of our house. Typically, older homes had 2x8 or 2x6 roof rafters spaced 12"-24" o.c. Most newer homes nowadays have pre-manufactured roof trusses that don't allow for a vaulted ceiling.
The ceiling joists that run between the exterior walls alongside each rafter are being utilized to resist tension from the vertical forces, not collar ties. They are much better at resisting thrust provided they are fastened to the rafters as well as to the top plates of the exterior walls.
There should not be collar ties between rafters above the ceiling joists.... period!
The blue circles show the important connections between rafters and ceiling joists. The existing rafters were only being anchored to each other with long nails. I decided to buy 3" x 9" simpson gusset plates to nail to each rafter ridge connection. I used about 12 simpson nails at each pair of rafters. This was a small investment I decided to make for added strength / security. Ultimately, I don't know if this was actually required but it gave me piece of mind. You can also make the gusset plates out of plywood.
In addition, I fastened the rafters to top plates with additional nails. Any ceiling joists that were sistered together received additional nails and blocking. Again... piece of mind.
There's also the question about the actual weight of the roof from snow/wind/etc. causing the roof to sag. I've given this a lot of thought, but then I realized that our roof has been this way for 120 years. In addition, we were adding intermediate walls in the design that would be fastened to the rafters.
The next step was to insulate the roof... Stay tuned!
The process for designing our 3rd floor took a very long time. Mostly because my wife and I are both architects with strong design opinions. Our compromise for certain design elements is usually to go with the most expensive option. Needless to say this was a very costly renovation with no corners cut for materials and fixtures. With that being said, we decided to compromise by doing all. of. the. work. ourselves. It took about 9 months to complete.... but well worth it in the end.
The inspiration for the 3rd floor bathroom and master suite was to focus on contrasting, modern and well-built fixtures and hardware that would pop out against neutral natural materials. We knew we wanted the following:
-vault the ceiling to open the space. Big debate about whether or not we needed collar ties, a ridge beam, and what material the ceiling finish should be
-reroute and reframe the stairs to open the space up
-bathroom fixtures.... black or brass. no brushed nickel or chrome please and thank you! also no plastic parts
-built in warbrobe extended floor to ceiling. no soffits. no wasted space. need to figure out material, are these custom built, etc.
-tile floor to ceiling in the bathroom. no large format tile. no 12x24.... please.
-a huge shower with a linear drain and a prefab kerdi slope.
-a huge slim profile waterfall shower head. the biggest shower head on the market.
-custom linen cabinets. no melamine or MDF.
-insulated and rated ceiling
-heated bathroom floors
-built in book cabinets
-floating vanity with either soapstone or marble top
To name a few. Below are a few images we took inspiration from in the beginning.
Love the black shower hardware and the tub filler.
love the toilet, shower glass, shower fixtures, wall tile, mirror, pretty much everything...
love the tile... both the floor tile and wall tile
love the ledge near the tub
love everything is this photo
not sure why i chose this picture but i love the linens. is that parachute?
in this photo i was trying to see how people were exposed the collar ties.
the brushed nickel really kills this shower.
Maggie, at this point, did not know what she was getting into..... this is one of the first days of demo... and we are discussing everything that needs to be demo'd (which is everything)...
This is a photo of inside our closet after everything was cleared out. When we first bought our house we had the contractor run new shafts to the third floor--shown here--which we ended up completely re-routing for the third floor renovation. One of the temporary projects in this house was to install a partition wall with an access door into a separate space from our "closet"..... yeah, time to demo it all....
Our previous insulation in our ceiling / roof....... broad loom carpet scrap!!
Yes..... i saved every piece of bat insulation.... and trust me.... there was a lot of it!
Bathroom demo.... can wait to remove this raised floor. Why is it raised?? bout to find out.
Maggie demoing the shitty tile in the old bathroom....
The bathroom walls are gone.... and being stored in my garage....
This was a fun evening after work: stripping bat insulation from the roof rafters of the attic. Word of advice: wear a long sleeve shirt and gloves. Don't handle baby's afterwards.
Bathroom demo almost complete. Still have to remove the carpet, floor boards and collar tie.
Here we are dismantling the old stair. I built this railing with blocking that allowed me to remove the railing balusters separately from the rails... this allowed me to move material and furniture easily up and down the stairs. Ultimately, this was all removed...
I would say this is my final demo photo before the new construction started. All that was left was to remove the rest of the framing for the ceiling.... and make the one million trips downstairs hauling lumber and trash into the garage.. We didnt rent a dumpster for this project.... so we spent the next 6 months or so taking 10 plus contractor bags of trash to the curb... which we stored in a full garage in the meantime. We saved every piece of insulation and framing for this project. We de-nailed every stud and re-used it for the new walls---crazy but saved us a lot of money in the end!
Brandon E. Young