How to Jack and Repair Antique Structures
No.1 The process to lift and repair this building is explained in this short pictorial primer. The damaged arias are located and exposed and the size and extent of damage is determined. If you are not sure, take a hammer and pound on the sill. It you get a high pitch dead blow sound the sill is solid. If the tone is low with a bass sound you most likely have a sill to replace.
No.2 Measurements are taken off the building and a field drawing is made. The drawing allows the measurements to be transferred to the horizontal lifting plates. All lag holes are then laid out, checked for accuracy and drilled in preparation to install the plates to the second story spanners and first floor wall studs.
No.3 The jacking plates are lifted by two men carring them up a ladder and setting them in place temporarely. They are lifted to the final location and timber locked to the wall.
No.4 when the plates have been alighaned properly the final 1/4inch pilot holes are drilled and the plates are lagged to the wall.
No.5 At this point the ground pads are located and the angles set. The angle of the pads is crital and may have to be set a few times until they are stable. The blocks and jacks are installed next and the post are measured and measured for length and cut. The posts are installed and light pressure is taken up in them.
No.6 Oak 4x4s are installed under the floor parallel to the foundation.Posts and jacks are installed vertically to support the floor are its proper height and to allow the house to be used with out interruption.
No.7 With the jacks in place and under load the weight can be taken off the foundation in order to remove the damaged sills. The floor frame work is measured for length and depth and all detentions are recorded on a field drawing. From there the measurements are transferred to the new sill timber and laid out accurately. The mortise and tenons are cut as well as joist housings as necessary in the sills. This work is preformed with skill saws and, Fostner bits and old fashioned chiseling. This phase of the project takes time.
No.8 The sill is moved into position to the inside of the jacking posts and set on to blocking at the same height as the foundation. The first fit is made to see if all the dimensions match each other. It is inevitable given the condition of multiple variables that all inside and outside dimensions will be perfect. The sill usually has to be backed out onto the blocking and turned up if necessary and have the adjustments made. Once the adjustment has been made the sill is turned and reset on the foundation. This is typical in every insulation
No.9 There are reoccurring situations that require removing a piece of the leading edge of a joist housing to stop it from binding on the joist or girder end. The condition is more prevalent on the beginning joist than at the end because the angle is less as the sill goes into place. Occasionally, a housing will be too shallow or a tenon too long by a bit. This is field work and there are a lot of adjustments to be made to get old buildings to accept new sills. Kind of like new shoes. It’s good to check and check again. These buildings were made by hand. Every piece of wood was hand shaped and custom fit. We have to do the same process only in reverse.
No.10 When the work is completed the sill should be properly sealed with a good oil bias product, lagged together and all post, wall studs, girders and floor joist should be a good fit and soundly connectee to the building. Remember that you only get one chance to do it right in 200 years.