how can i lift a porch roof in order to replace the cloumns and the t&g flooring, the porch is 24'w X 8' deep, there are 4 columns, should i lift the entire roof or a couple at a time.
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It depends on how well the elements of the roof structure is connected. ( I removed the trim from one porch roof edge and found the 'structure' was a series of unconnected beams spanning from column to column. ) I've seen roofs raised two ways. One used 4x4 temporary columns with bottle jacks to lift the 4x4. These were based on the porch floor and the floor work was done around the jacks which were later removed and the floor finished. One used built up temporary struts set at an angle and based on the ground with boards set at a slope below the strut ends. The struts were driven down the inclined surface, bringing the struts to a more vertical position and raising the roof. T
We do this fairly often for customers. Every case is a bit different. If the porch roof is wrapped with aluminum flashing (usually the case we come across), it can be difficult to prop up the roof without damaging the aluminum.
Anyway, you neeed to find a solid place along the roof edge to place your jack. There should be a built-up beam along the front edge. Make sure you are jacking aginst the beam, not just the facia. Make sure the jack will be supported well on the floor underneath this point. You may have to place props under the porch to insure the jacking point is solid. You can use a second jack underneath, pressing against a suitable heavy board laid on the ground.
Cut a 4x4 prop to the correct length, and jack the roof structure up just enough to slip one column out. You don't need much. A small hydraulic jack is all you need in most cases. The column should just be toe nailed in at the top. If it resists pulling free, cut the nails with a recip saw.
Remove the column and the flooring underneath it. Replace the floor boards in that area, and place the new post. Then remove the old flooring up to the next post, and repeat the jacking. This way you only have one column removed at a time.
However, be aware that is the floor is failing, the under structure is often rotten, be ready to replace joists if needed.
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