Jacking up a house 7

[Robbiee]

Hello,
A contractor wants drawings for jacking up a house. The attached sketch explains his and my ideas for how to do it. The contractor has done only one similar job for a farm building. The reason for jacking up is two-fold: 1- to replace badly cracked foundation wall and 2- to raise the basement height by 16". My proposed sequence of work is:
1- provide the shoring beams in the basement as shown. Don't jack-up the house yet.
2- install the temporary lateral braces
3- demolish and rebuild the foundation wall one side at a time to the current height.
4-Jack-up gradually and evenly about 1/2" at a time to a height of 6" above the final height. Temporary braces to be removed during jacking up
5- Install two additional courses of blocks to the new height.
6- three days after installing the additional courses of block, remove lateral braces and Lower the house to bear on new wall.
7- Drill and install new anchors.
8- remove jacking system.
I am doing this for the first time therefore any input from you will be deeply appreciated. Thanks

 

[Robbiee]

Oh, Sorry, Here is the attachment.

 

[MiketheEngineer]

Don't forget to un-hook the plumbing, wiring, sewer and HVAC first

 

[BAretired]

You are picking up the joists 4' from the outside wall or 7' from the central beam. What provides the required hold down force at the central beam?

I agree with disconnecting the utilities first.

BA

 

[BAretired]

The two short shoring beams don't seem to have any purpose. Why not eliminate them?

Also, removal of lateral braces in Step 6 could produce instability before the house has been set down on the new foundation.







BA

 

[Robbiee]

Thanks Mike and BA. BA,
I did not understand your question about holding down force. The joists are not continuous. They are spliced at the central beam. The short beams are supporting the existing central beam, which is bearing on the foundation wall that needs to be demolished. Also it is needed when the beam will be jacked-up. I guess they can be removed and replaced with a support and a jacking point at each end of the central beam.
The lateral braces have to be removed at some point to allow the house to come down 6" and bear on the new wall then the house will be anchored immediately.

 

[BAretired]

I realize the joists are not continuous. Each joist is 11' long, supported at two points, giving you a four foot cantilever and a seven foot back-span. At the end of the cantilever, you will have a point load from the weight of the roof and wall.

Each joist will have a downward reaction on the shoring beam and an upward reaction on the existing central beam. What prevents the joists from lifting off the central beam?

You don't need the short shoring beams. You can jack the central beam directly in locations of your choosing.

Removing the lateral braces before the house has been placed on the new foundation is risky and should not be done. You need a system where the braces can remain in position until the house is permanently attached to the new foundation wall.

I believe there is a better alternative, but I will await your response to the comments above.


BA

 

[ztengguy]

So are you putting two beams through the house, left side and right side, or are you haveing three, and picking up the central beam? With the shoring beam left to right as shown, can the existing central beam span from shoring beam to shoring beam, since its seems to be a three span condition now?

Kinda confusing drawing

 

[cooperDBM]

I think any required lateral shoring should be internal to maintain the integrity of the building in the case of it going out of level. The lifting system has to be robust enough to prevent the building falling sideways.

When I lifted my house the transverse lifting beams were extended beyond the walls to support them directly (joist ends had rotted). LVLs were run around the perimeter of the building attached to the bottom of the wall studs (balloon construction). Blocking was then placed between the top of the lifting beams and the bottom of the LVLs. I assume from your drawing that your transverse beams are also picking up the center beam.

I used a very experienced house moving company. They had quite a nice automated manifold system for their jacks. Piece of cake for them and reasonable in cost.

 

[Robbiee]

Thanks for the comments.
BA,
There is a wall that bears on the central beam. The wall extend from floor to the ceiling joists, which are connected to the roof rafter with vertical members. I know, I should have shown this load bearing wall on the roof sketch. But, now that you have mentioned this point, I am thinking of the 6 ft wide opening in this wall that I need to temporarily infilled with studs to create a continuous load bearing wall.
Ztengguy,
The shoring beams are 4; 2 short ones support 2 long ones in addition to supporting the existing middle beam which has 2 supports. when jacking up, jacking points will be used as shown.
cooperDBM,
The house has partitions with drywall still in place. Are you suggesting internal horizontal bracing to keep the corners square?
As I mentioned before the sketch is a combination of the contractor's and my ideas. When I was involved, the 4 beams as shown were in place. I am trying to see if this can work. If it doesn't, I will tell him so and what needs to be done.

 

[Brad805]

Are you confident this guy has the experience to do this? The cribbing and jacking equipment used to move our farm house kept the home very stable at all times. There is a lot of experience that goes into this type of work, and quite frankly, that is more valuable many times than an engineering procedure. If this guy does not have the appropriate insurance for the work, he should find someone that does. If not, you could end up being his insurance.

 

[Robbiee]

Brad,
I mentioned that he has successfully done one house in the past. I did ask him if he is comfortable doing this which he answered very confidently: Oh yeh. I have no idea if he has insurance. Thanks for the comments.

 

[BAretired]

Brad805 makes a good point. It is better to hire a contractor with experience.

Why is the existing foundation wall badly cracked? Was it the result of settlement, frost heave or other soil movement?

Are you planning to re-use the existing strip footing?

Will a masonry foundation wall be adequate to span an additional 16"? Have you considered a new concrete or PWF wall?

BA

 

[Robbiee]

BA,
A big tree near the house was partly the reason for the cracks. The footings are 4 ft below grade. new height of the basement is 7'. The existing strip footing seemed to be in good condition and the new foundation wall will be reinforced. It is not my choice to hire a contractor. I am doing this for a contractor who is at the same time the owner of the house. Masonry is his choice. Thanks again for your comments.

 

[Hoaokapohaku]

I'm not an expert at this, but I have raised two houses, both for very similar purposes as your project. One was lifted with jacks, the other with a crane. I've also been involved in the transportation end of a couple moves performed by professional house movers. Also, I think this is the first time I've ever said "watch TV" for a solution, but in this case there have been some very good shows on house moving by experts. There have been episodes of "Modern Marvels" showing this, as well as "Heavy Haulers." With a little searching on Hulu or Netflix, you can probably find the episodes. For and example of how NOT to do it, the very latest episode of "Ice Road Truckers" showed a house move of a building very similar to the one in your drawing being lifted and moved across the city in Fairbanks, AK. They threw a couple beams under the house, got forks from a forklift under them, lifted the house with the forklift and backed a truck under - very dicey.

One thing typical of other structure lifts that is different than yours is that typically all the shoring beams run in the same direction perpendicular to the floor joists. Seems to me that this is simpler and there are just less ways for things to go wrong. One potential problem that I see with the present scheme, is that it possible to jack the longer beams higher than the short ones and lift the long beams off the short beams - not good. This probably wouldn't happen if you have the kind of hydraulic manifold system like Cooper mentioned above, but since both you and the contractor are trying to figure this out, I'm assuming you probably don't have that kind of equipment and will be forced to manually operate each individual jack. I would consider placing two additional long shoring beams placed just either side of the central existing beam. Then, relocate the short shoring beams perpendicular to and underneath the four lengthwise beams, and place all jack locations under the short beams. I would put 4 jack locations under each of the two short shoring beams in locations so that any two jacks located on opposite sides of the building central beam are capable of carrying the load of that beam even if the other two jacks were not there at all - 8 jack locations in all.

If you don't have the manifold type hydraulic jack system, use screw jacks instead of hydraulic jacks. They have plenty of lifting capacity and allow very precise control so that you can raise them in very small equal increments, allowing you to raise them one at a time (applying common sense to the order) while moving the structure out of level only a tiny amount.

I wouldn't bother with the temporary bracing. Instead, design the cribbing to provide safety. I would think that if the cribbing is designed and placed in like manner as would be done to support a crane, that should be more than a sufficient safety factor and that house won't be going anywhere during the construction unless there is a hurricane, tornado, major earthquake, etc. Any of those occurrences would probably treat the temporary bracing as so many toothpicks anyway. Crane cribbing must be designed so that the entire weight of the crane and load can by supported by any one of the outrigger supports. By the way, the cribbing as presently drawn would not be considered adequate for a crane. Assuming the cribbing has adequate ground bearing area for the load, the timbers must still be placed side by side the entire width of the cribbing in both directions. In other words, fill in the empty space between the 8 x 8's with more 8 by 8's.

 

[Brad805]

One small project is a little different, but I will assume you know his character.

For my project they used 20" diameter pipes from end to end of the home. They had cribbing stacks approx. 6' square in plan (maybe six per side of house) that extended from the slab to within 6" or 12" of the underside of the pipe. The pipes were kept spaced apart with steel and cabled together with chains and boomers. Once all the cribbing and jacks were in place they hooked all the jacks up to the hydraulics, balanced them, and slowly lifted. They also had a manifold system to lift all the hydraulics together. They lifted to the full extension of the jacks, added cribs and repeated until it was to the height as needed. This house was around 1800sqft and weighed in at about 80,000lb once it was on the truck and they got the weights from the trailer load cells. That was the best $18k I spent.

Have you sat down with him and went over his ideas? The amount of cribbing and materials to lift the home may surprise him, so knowing his intentions earlier will help avoid re-doing the plan many times. This will also serve as a test to understand how this might proceed. Insurance for this type of project is not too easy to come by (and has interesting restrictions/coverage), so you should make sure you understand his reasons for getting you involved.

Good luck

 

[cooperDBM]

Ailmar,

Here's a link to the pictures of my lift, "

https://www.facebook.com/media/set/?set=a.134854857285.108927.639807285&type=3&l=5b113764d2".

The actual lift starts about picture 35.

For lateral bracing, the house itself needs to resist racking and differential movements. This is best done internally or on the outside of the sheathing if the cladding is removed. The internal walls will do a lot but it may still be worth placing diagonals on the walls and across openings (screwed into each stud) particularly if it's more than a bungalow. The lifting system itself needs to be laterally stable for the conditions you expect to have. With that the external lateral bracing shouldn't be required. There's always increased risk during the actual jacking but at least you can pick you time for that when conditions are good.

My lift was also about $18K. Everything else was a small fortune.

Good luck.

 

[BAretired]

What a great series of photos, cooperDBM.

BA

 

[Robbiee]

These are way more generous comments than I expected. I have incorporated many of your comments into the sequence of construction. Thank you all for that.
cooperDBM:
Like BA said, these are indeed very great photos. Very similar to what we will be doing.

 

[charliealphabravo]

Wow, that's impressive.