We needed to demolish a chimney.
The cinder block chimney was built in 1950 from low quality materials and was falling apart. Officially condemned. Not usable. Fire hazard. Chunks of it were falling off onto the ground. The chimney had to go.
The cabin with the chimney is located in South Lake Tahoe and was built in 1927. More info on the cabin is here.
I like dangerous instructables that are bigger than me. That's why I posted this one.
So... should we try and yank down the chimney ourselves?
Step 1: Risks of DIY: Don't Get Crushed!
"Just stand far away, so you don't get crushed!" was not good enough for us. There were other risks besides getting crushed.
We decided on using a cost/benefit analysis.
1. Personal harm by crushing (easily contained by standing far away)
2. Damage to car
3. Creating a large, expensive hole in side of cabin
4. Destroying the really cool, historic, river rock fireplace inside the cabin (pictured)
1. Remove useless, ugly, cinder block chimney
2. Save money by doing it ourselves
3. Have fun tearing down a chimney with our car!
4. Install fireproof shingles and save historic cabin from forest fire
The cost/benefit analysis showed equal costs (4) and equal benefits (4). But the forest fire concern was more important than the other points.
We needed to reroof with new fireproof asphalt shingles. The old wood shake shingles were an extreme fire hazard. When there was a forest fire (guaranteed at some future point), the firefighters would flag the cabin as "do not protect" because of the wood shake shingles. It would be a lost cause.
The roofer said if we removed the chimney he would patch the resulting hole at no extra cost. (?!)
Step 2: Ask the Neighbors What to Do
One way to make a decision is to ask around. We asked around in the neighborhood.
"You need a front-loader [bulldozer] and a chain", said our neighbor. He had done it before and I believed him. He keeps a front-loader parked in front of his house and uses dynamite at his job. His name is X-ray.
"We did it with a Ford F-250 pickup and a steel cable", said another neighbor. I didn't see the actual demolition, but I had inspected the result and saw it cleanly pulled the masonry away from the 80 year old cabin with no damage to the cabin! We were impressed that you could just yank a chimney down and not damage anything (except the chimney).
Are you surprised that two neighbors have experience tearing down chimneys? We were, too.
But we didn't have a front-loader, and no chain, no steel cable, and no big pickup truck. So we got an estimate from a contractor. The contractor wanted to erect scaffolding and chop the chimney apart bit by bit, for almost $5,000! He was afraid of damaging the cabin by just yanking the chimney off. We were afraid, too.
Of course I also searched instructables for other "chimney yanking" projects before posting this instructable. I found one! It didn't seem related to my project even though I liked it a lot. They built a chimney instead of pulling one down.
We decided to just yank the chimney off ourselves, using a rope and my 2001 Honda CRV.
Step 3: Find a Strong Rope
We used a a 15 year old 90 foot double braid nylon boat anchor line from New England Ropes. We already had it so it was easy to find.
The rope is a 'dynamic' line, meaning that it stretches a lot when loaded. A steel cable or 'static' line does not stretch (unlike the dynamic rope we used). The anchor line we used has a very similar load and stretch specifications to a climbing rope. In fact we used that same rope for rock climbing many years ago when we couldn't afford a proper climbing rope. I think it was $40 from West Marine around 1994. I'm not sure of the size, but you can see the pictures. It is easy to tie good knots with this rope.
Knots are important, but are an ancient tool and not the focus of this instructable, so they are not explained here. Besides, any knot will probably work as long as it does not come undone and you don't want to untie it later.
Another rope you might be able to use is the ubiquitous yellow plastic three-strand polypropylene rope. This is a very common, strong, and cheap rope that you have probably seen before. I opened my closet and took a picture of a length of 3/8th inch wide rope, which I happen to have. We didn't use this rope. I think it would work too, though, if you doubled it up. It is a static line and does not stretch much, so you might risk tearing the bumper off your car? I would have risked it anyway, if I had needed to, and just drove very slowly. Of note, it is hard to tie good knots with this type of rope, but its super cheap. I got mine free somewhere so I don't know how much it costs.
Make sure the rope is long enough so that the chimney does not fall onto your car when you pull it down. If you decide to use a rope that is too short, please make sure you record it to video and post it on instructables!
Step 4: Remove Metal Flashing With Claw of Hammer
Peel back the flashing and tar of the cricket.
Step 5: Tie the Rope to Your Car
We wrapped the rope high on the chimney. We were worried that the sharp corners of the cinder block might cut the rope (not a problem). The knot we used was a figure-eight on a bight at the end of the rope to make a loop. Then we fed the entire length of the rope through the loop to make a modified girth hitch around the top of the chimney.
We used a bowline to tie off to the Honda.
Step 6: Drive Away With Rope Attached to Chimney
I drove slowly into the woods behind the cabin to tension the rope, only 2 or 3 mph. I stopped when I felt the rope pull tight. I didn't want to destroy the cabin, or my car! The rope was now quite taught.
I began revving the engine over and over, driving forward a few feet, and pulling the rope even more taught each time. When I released the gas pedal, the springiness of the rope pulled my car backward to its original position. I did this 10 times or so, giving a little more gas each time.
A dynamic rope is quite stretchy, like a rubber band. Although my car was only ever in the forward driving gear, every time I let off the gas my car would go backward about 2 or 3 feet. Back and forth the car rocked, like trying to get a car un-stuck from mud or snow.
Step 7: Timberrr!!!
I got back in the car and tried a few more revs and the chimney finally popped off cleanly. No damage to the cabin, except for hole left behind by the missing chimney!
It cost $200 to have the debris hauled away. We theoretically saved $4,800 over the cost of the contractor, and had some excitement. I think the demolition hammer rental was $60, but we didn't even need that.
Amazingly, we were able to untie the bowline knot in a few minutes of struggling. I never got the figure-8 on a bight untied, but we continued using the rope for other projects anyway.
Step 8: More Info About the Chimney Demolition Project
In the end, it felt a lot better tearing the chimney down with an old rope and a honda, rather than pay a contractor $5,000. Maybe we were lucky that it all turned out OK. The main thing is to not get hurt, and no one did, so it was a success!
Before trying to yank the chimney off, we spent a few hours chipping away at the spot where we thought the chimney would crack off. We even rented a demolition hammer, which is like a mini electric jackhammer. DO NOT BOTHER WITH PRELIMINARY MASONRY DEMOLITION. When we pulled the chimney down, it cracked off in a completely different spot than we had planned.