In my line of restoration work, I spend a fair amount of time straightening out the sags in a house that set in over time. Porch roofs are typical victims of gravity as the roof layers build up and the pier blocks below the porch columns settle. Whenever I’m called on to lift a porch roof back into its original position, I rely on simple built-up posts made of 2x4s to raise the roof. Sure, house jacks will do the same thing, but first you have to buy or rent them and then get them to the job. If you need a lot of jacks, the cost can add up fast. These 2×4 jacks are inexpensive, and they can be recycled into building components. Here’s how they work.

Let’s say the roof is 100 in. above the porch floor, and it needs to be 101 in. As shown in the first drawing, I prepare a two-piece temporary column that adds up to 101 in. One-half of the column rests atop its mate by way of a 2×4 block that is affixed to the side of the 2×4. The block should be about 1 ft. long and attached to the 2×4 with six 12d nails. The lower end of the block should be no more than about 2 ft. from the top of the post.

To lift the roof, I put the bottom half of the two-piece column where I want it on the porch floor. With the column half leaning toward me, I put the top of the other column half under the rafter that I want to lift. Now, as shown in the drawing, I snap the two halves together, lifting the roof. To stiffen the temporary columns, I secure their halves either with screws or with pneumatically driven nails. Then I add diagonal braces to the columns and the porch to stiffen everything while I install the permanent columns.

In my experience, this method is best used to lift a roof no more than about 1 in. at a time. But these columns can, of course, be used incrementally. For a 20-ft. porch, I use five temporary columns to make the lift.

Lon Marshall, Washington, DC

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