Replies

1. 
   jimblodgett | Jul 07, 2004 01:52pm | #1

   Take it slow; you'll hear it popping and creaking as you lift.  Once you get a little tension on your jacks, crawl out and take a look around.  Look at reveals around doors, cracks in wall coverings, maybe lay a level(s) here and there carefully noting the change in bubbles as you lift.

   Above all, be careful.  Jacking a building is pretty straight forward, but the dangers are obvious (and not so obvious).  I've always thought screw jacks are safer than bottle jacks because a hydraulic bottle jack can rupture and fail.  We rent big screw jacks at our local yard that work well, but they ARE slower than hydraulic jacks.

   If you think you need a 10 ton jack, use a 20.  But there's really no way you should be lifting that much weight at any single point - use several jacks in a line instead of a single jack relying on a structural beam.  "Redundancy" is what I generally try to keep in mind when choosing jack placement points.
2. 
   JerBear | Jul 07, 2004 01:54pm | #2

   A little at a time usually.  Mostly it depends on the house.  Are the walls plaster? (less flexible).  Are there doors or windows that could get knocked out of square?  Just remember that when you jack something, especially a main beam, you are transferring stress loads so be aware that you may need to jack it in more than one place.  I usually go maybe a half inch up after you have reached the heavy tight point and let it set for a few days,  creep it every few days from there.  Then again it may go right up without any real problems.  Also, listen for the creaks, groans and gives in other areas, if you hear a loud "crack", back off a little and check things out,  that's the stress transferring...you know, like when you get up in the morning, or when the spouse tells you your birthday is being spent at the inlaws.

3. 
   billyg | Jul 07, 2004 02:20pm | #3

   Also, be careful what you use as a foundation for the jacks.  Use big timbers and/or steel plates placed over heavy framing members.  Distribute the load.  One time I was jacking a large house from the basement.  Suddenly the concrete slab under the jack failed, sending the jack and support post flying like missiles.  Luckily no one was standing in the flight path.  Take it slow and think about what you are doing.

   Billy

4. 
   RenaissanceRestorations | Jul 07, 2004 03:21pm | #4

   1/4" - 1/2" max per day is the rule I used last time I had to jack up an 1880's carriage house. Granted it's not much of a move, but it gives the building time to "adjust". Chances are you will get some cracks in plaster, maybe a door that won't open/close anymore, and will need to be shaved. Use lally columns in conjunction with the jacks in case a jack fails.

   JoeF

   Renaissance Restorations
   Victorian Home Restoration Services
   http://www.renaissancerestorations.com

5. 
   DanH | Jul 07, 2004 05:20pm | #5

   A lot depends on the structure above, but 1/4 to 1/2 inch per day is probably the ballpark. Do expect some cracking of plaster, trim popping loose in spots, etc, but with luck this will be minimal.

   It probably helps to be doing it in summer when humidity is high. Turn off the AC and let air into the house to humidify things.

6. 
   csnow | Jul 07, 2004 06:02pm | #6

   Spread the load if you can using several jacks.

   Once the structure starts to resist, go slow.  Great if you can do just a little incremental lift per day over time.

   Do not leave weight on hydraulic jacks for very long.  They may lose their lift over a few hours.  Use some sort of screw jack or bracing to hold your progress.  Or, simply use screw jacks in the first place...

   I'm a big fan of these clever jacks for this purpose.  I just bought a bunch more for a couple of sill replacement projects I have going. Very convenient to use, and reasonably priced.

   http://www.gearshop.com/acb/showdetl.cfm?&DID=21&Product_ID=1297&CATID=22

1. 
   DanH | Jul 07, 2004 07:38pm | #7

   Yeah, those look nice.

7. 
   JohnSprung | Jul 08, 2004 02:13am | #8

   First, minimize the transfer of stress to plaster surfaces.  Pull the baseboards in the affected area, and rake out the bottom of the plaster to maybe 1/2" above the top of the sole plate.  If you have existing cracks in the plaster, rake them out an inch or more wide.

   I've done this using one bottle jack and lots of cribbing and blocks and wedges.  I'd build up a stack of blocks and wedges alongside the jack at each point, and keep it up close in height to catch the load if the jack let go.   Then transfer the load to the stack, and move the jack to another lift point.

   -- J.S.