Hi,
I recently purchased an old house with structural issue – the floors have sagged about 4″. The house is probably 100+ years old. Dimension is 22′ x 45′. It has 2 levels and attic. The foundation walls are built of fieldstones. I have water in the basement & I am working on a solution. There is an open sump pit in the non conforming basement.
My question is how much does the house weight? I have hardwood floors & wooden siding. When I plug in the numbers on this site, it comes to 71 tons. Is it safe to assume the weight of the house is 90 tons?
There are two beams on the driveway side, they don’t run the entire length. The purple color lines show rough position of the two beams. Beam on the left has rotted and sagged. I have added the adjustable posts to keep it in place as the current support posts are deteriorated.
Q1. The beam on left is 20ft long. Can I support it with adjustable posts only (marked green in the picture)?
Q2. How much load will be on each of the three new posts (marked green in the pictures). Each of these jack post has working stress 8090 lbs. and factored resistance 11,650 lbs. Do I need more jack posts or three is enough? I want to remove all other existing support posts marked red.
Q3. I am planning to use bottle jacks to lift the house. What should be the capacity of the bottle jack? 10 tons or 20 tons?
I would highly appreciate it if you could take a look at the picture and share your thoughts, suggestions & recommendations.
Thank you for your time & feedback, have a great day!
Replies
Before you start worrying about post capacity you need to think about what they will be sitting on. You can't just put those posts on the basement slab. You need footings sized for the load and soil type.https://www.dli.mn.gov/sites/default/files/pdf/ms_soils_classification_and_bearing_table.pdf
Good point, thanks for sharing the link. I will get the footing sized for the load and soil type. Thank you.
It's a good call to estimate the house's weight at around 90 tons given its age and materials. For the 20ft beam, make sure the adjustable posts are spaced properly to distribute the load evenly, and it's wise to consult a structural engineer for precise guidance. Three jack posts with the specified working stress and resistance might suffice, but it's always best to double-check with an expert. When it comes to the bottle jack, opt for a 20-ton capacity to ensure you have ample lifting power.
You need to engage a structural engineer NOW! This is not some trivial thing happening to you, and there is only one engineer on the site
Thank you for your feedback. I did contact some structural engineers before, they didn't seem interested, as my plan is to add new beam, not to replace the existing one.
I will consult with structural engineer before I proceed. Thank you!
even if you pull all the plaster and lathe off the walls, you might not be able to lift the building to level unless you do this over a long period -- weeks or months maybe.
the plumbing and the chimney need to be isolated from what's getting jacked.
if you use bottle jacks, then use them to lift, but have adjustable shoring posts [or at least adjustable lally columns] taking up the slack as you lift.
the beam rolling under load is a big concern.
good luck, but's that no substitute for experience -- might consider hiring someone who does shoring and house-moving for a living. they will have the proper equipment to shore up the building while you do the work of pouring the new piers and installing new beams and posts.
1. You need to post more photos of the connection of the post to the beam and floor diaphram.
2. Has the beam deformed, not straight? If so, Jack it up slightly and even wet it to allow to deform (but only after following shoring steps below first)
3. Where is the sag, directly at the beam locations?
The lally columns would be fine, the 12k lb load will work if it's just the floor load above for sure. Are there walls above that stack, and or walls above that might take roof load from above? If so, prepare to beef up and upsize the lally columns. If you're going to tackle this you need to over engineer if you don't have structural sheets stamped. That's the method of carpenters when shooting off the hip, if you have to sharpen calculations, you're under sized..
4. Can you visualize 100% the load paths? If so, ensure you have temp shored up all loads before displacing anything. Ask if you're 1% unsure of anything.
5. Pour footing pads thick enough and wide enough to distribute the loads. The answer is 12" thick x 36"x36" for standard overkill. You can do it right in the slab, or saw cut the slab first. Either will work if you have no plumbing underneath.
6. Are the joist framed flush with the current beams? If so are there hangers or are there pressure blocks between the joists that the joists are nailed into? Replacing the beam is way easier because all you need to do it shore up the joists fully with braced 2x4 walls all the way, and mind whether there are point loads from above directly on the beam currently so you can deal with that first, then cut out the beam and slide a new beam in its place.
If you're set on adding a new beam underneath, make sure it's wide enough to pick up the joists from either side with plenty of bearing 3" min, and put it in place after shoring all joists up.
Do you understand all of the above?
You say that "the floors have sagged about 4″." I would ask that you clarify that statement:
- Is it "sag" (along a beam or joist span) or is it "settlement?"
- Have you pulled a string along the beams to evaluate their profile?
- You say there's a water problem - perhaps that may have contributed to the post's concrete pads to sink deeper into the soil.
You cannot evaluate the loads and forces involved simply by guestimating the total weight of the house. That is only the dead load. Whatever permanent solution for the issues you have also has to consider the Code mandated live load.
- There is more at play here than what you're considering. You HAVE to understand the load path from roof down to the ground that the structure sits on.
- No one on here can (or should) try to calculate the load on any given joist, beam or post without understanding how the loads from the upper levels get there (the load path).
- Using adjustable posts may have Code restrictions. Some manufacturers required that the adjusting screw be totally encased to concrete to meet Code.
- As far as bottle jacks go, there's no such thing as too much capacity. They need to at least be able to handle 3x the estimated/calculated load (for safety). As stamant noted "if you use bottle jacks, then use them to lift, but have adjustable shoring posts [or at least adjustable lally columns] taking up the slack as you lift." The total cylinder extension (stroke) of the bottle jack may not be enough and you'll have to add to the cribbing it sits on at some interim position, hence the stamant's comment about the shoring posts.
Can you ultimately eliminate the "sag?" Not at all likely unless you perform the work over a looong period of time. Probably somewhat, but doubtful you'll get all floors level. After all, it took a century to get to where it is. See stamant's comments above - especially the 2nd paragraph.
The walls above, perhaps some cabinetry, door frames, ceilings, etc. all have adjusted to the movement over 100 years. Various modifications/alterations over the years likely just accommodated the sag, out of square, etc. You may be forced into redoing/repairing that work due to damage from the lift. More than likely you WILL be patching plaster/drywall.
You will need to provide proper foundations for all of the new posts (possibly the existing ones as well).
Your #1 goal should be to insure that the structure is safe for all loading conditions. Whether or not it is feasible to eliminate the "sag" should be secondary.
All very good comments above.
Consider that there will be unforeseen circumstances that you will have to resolve "on the fly." Best to have a licensed structural engineer involved before you even start acquiring materials. FWIW, most engineers do not want to get involved in this kind of challenge as it consumes way more site visits and design/analysis time than major commercial or new residential work. Most homeowners would cringe if they were billed for actual time involved. As the owner, your liability ends when you sell and move on to the next rehab project. An engineer's liability continues well after that.
[CT licensed structural engineer]
Not a pro, but have you considered shoring up the current beam (appropriately sized footers and columns), removing the relevant floors and ceilings, and then sistering joists and shim+strap the ceilings to bring the new floors and ceilings to level?
This has the advantage of not disturbing what's settled: not having to replace or adjust every door and window, not popping all the plaster walls, not tugging the mechanicals, and not pushing loads onto parts of the house that haven't dealt with loads/strain. All that would have to happen even after you've spent months slowly raising the beam back up.
Again, I'm not a pro, but what I've seen in New England where all older homes have settling is shoring, sistering, and either full replacing the ceilings + floor, or (more commonly) shimming and layering on a new floor. Happens in "inexpensive" homes and $1.5MM+ homes alike.