My house was built in 1910. A few weeks ago while I was in the basement, I noticed one of the floor joist above me was not parallel to it's sister, but about 3/4" below it. The wood had split. I noticed that the portion behind it (about 2' to the wall) had an odd floor pattern with sloped joists running the opposite way, and realized that it was under the hearth. Ok, I'll have to jack that up and figure out how to reinforce it - the house IS old - so I got a jack, and after 3 weeks of half turns, I noticed the wood is constricting under the jack, not raising. So now that I'm actually paying attention... The sister joist also has cracks, but is not bowed. I start to really look at the fireplace construction. The chimney of my fireplace straddles the foundation, meaning on the inner portion there is no additional masonry underneath. The odd floor joist pattern is under the fireplace. Is this ok? My fireplace has always worked properly, the chimney doesn't lean, and I've never seen a crack. I have no idea what to do, and I don't have disposable income right now. (of course I can't let my house go to pieces either! I can't find any example of this type of construction, or how it was corrected.
Fireplace Foundation, or Lack Thereof
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WoodyIsGoody
Minister of Fire
The wood is crushing under your jack pressure because you didn't properly distribute the force along the joist. You need an I-beam (or at least a bigger timber) between the jack and joist(s). It's important to raise it evenly so you may want to consult someone more experienced.
Squirrely
Feeling the Heat
A jack is a good idea. A scrap of 4x6 long enough to reach to each adjacent joist will act as a guide so that when you raise the jack, only the sagging joist will come up to the level of the others. To spread out the force of the jack head to keep it from gouging the wood, try a small scrap of 3/4 plywood. It should work pretty good because it's a compressed product. Or better yet, a small 1/4 inch thick foundation plate from Home Depot will do the trick. It's just a 3 x 3 inch piece of steel with a hole in the center which will be smaller than the jack head.
For a permanent post, this one is $40 from Northern tool. It reaches from 4 to 8 feet.
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Greg
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Ashful
Minister of Fire
Old joists also sag and crush when they're rotten, or infested. Time for some photos, so we don't need to read your mind's eye.
You should have no wood under your fireplace or hearth extenstion at all. I would say it is time to have a pro look at it
We get the impression from your many comments that you are under the belief/practice that ALL chimneys & fireplaces have to be brought up to today's current codes -- or be abandoned?
If we were to apply such strict code application to wiring, or earthquake, or wind-related, or insulation codes, or fire code -- the majority of us would have no place to live!
No that is not true at all. But once you start working on it then it does need to be brought up to code. And there can be some serious safety issues involved so having a pro inspect periodically is a good idea. For example in this case ehen things start to sag cracks can open up allowing coals to get down to that wood underneath causing a fire. I have seen it happen and result in a fire.
So no i dont care if everyone brings their chimney up to code. I do care that everyone makes sure their system is as safe as possible.
You do realize i work on chimneys every day and when cleaning we see all kinds of code violations. We inform the customer let them know the risks and it is their decision from there. There are some cases where there is a clear and immediate danger and we will in those cases say it should not be used. But that is rare. In most cases we give them the report detailing any issues. From there it is up to them
Ashful
Minister of Fire
Not arguing with you at all, but this is a catch-22 situation, as it can escalate the cost of a small repair by orders of magnitude. My house isn't unusual for an older house, in that I have a timber foundation under my firebox, and FOUR stories of masonry stacked atop that. It has held fine for at least 240 years (possibly 280 years), and I suspect it will be around long after most of these "to code" installations have failed.
Yet, there was a need to extend my hearth, as the wood floor ran right up to the front of the firebox (also heavily used and totally fine for 240+ years). Would I want to chance causing a failure in 4 stories of structurally-integrated masonry, to replace that timber foundation, in the name of bringing it up to code when extending my hearth?
What about the thousands (tens of thousands?) of old houses around with wood lintels in their fireplace? Once you need any repair to that fireplace, are you forced to change out a wood lintel that has been operating just fine for 200 - 300 years? Evidence of many restored homes and restaurants in my area indicates this is never done, even if it is a code violation.
I bought a house built in 1906. Same thing with the hearths in my house. I have four and they were basically sitting on wood shelves. Two of the shelves were rotted away, the mortar was holding them up.
The two rotted ones were taken out by tearing out the bricks and then removing the old wood. I built a box with cinder blocks on a concrete foundation. I filled that up with gravel and compacted it. Then I made a 3 inch concrete slab on each one and laid half bricks in a Williamsburg pattern on a coat of thinset mortar. You do not have to worry about a mortar joint between the bricks. Just fill the cracks between the bricks with fine sand.
I mixed all the concrete in a wheelbarrow. It took about a week for both with setting and curing time included. It cost about $400. The two hearths still on the wood shelves are not used, I will fix them one of these days,
One of the hearths I fixed has my stove sitting on it.
The two rotted ones were taken out by tearing out the bricks and then removing the old wood. I built a box with cinder blocks on a concrete foundation. I filled that up with gravel and compacted it. Then I made a 3 inch concrete slab on each one and laid half bricks in a Williamsburg pattern on a coat of thinset mortar. You do not have to worry about a mortar joint between the bricks. Just fill the cracks between the bricks with fine sand.
I mixed all the concrete in a wheelbarrow. It took about a week for both with setting and curing time included. It cost about $400. The two hearths still on the wood shelves are not used, I will fix them one of these days,
One of the hearths I fixed has my stove sitting on it.
And we work on lots of old houses with old wood lintels and yes we pretty much ignore them but we will not rebuild any part of them because it means we are taking on the responsibility for that fireplace. And yes many have been there for 100+ years but how many burnt down in that time? They also used to run single wall pipe up through the house to a chimney built on the attic floor. And they used to have wooden chimneys with just a parge coat inside. I understand what you are saying but that doesnt mean there is no potential safety issue
There's a good reason to keep wood away from high heat. My wife grew up in an all chestnut log inn that was made during the chestnut blight in the great depression. It had no central heating, just a large stone fireplace on the main floor and a matching smaller one above in a bedroom and a kerosene heater. The place wasn't really designed to be a year round residence but by the time her parents bought the place it was used as such. All was well until one very cold winter storm when we had both fireplaces going strong. About 3am folks in the upstairs bedroom smelled smoke. The stones had heated up enough and perhaps embers made it through a crack and pyrolysis started cooking the timber supports. Fortunately for all the fire was dying down and we were able to put out the smoldering timber with water, but it could have been much worse. That is the funny thing about pyrolysis. It is a ticking time-bomb and one never knows when conditions are right for ignition.
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