If you have a continuous soffit vent in your attic which needs replacing, you can either get one which is a similar size, and fit it in the same place, or you can get a smaller vent and repair the larger hole. Which you choose depends very much upon economics, and how much you want to ensure that the soffit vent you have choosen is a good stand-in for the one you are replacing. You could also see the advice of a professional in order to find exactly the right soffit vent for your needs. Replacing a continuous soffit vent is not very difficult, and can be easily accomplished by following some basic instructions.
Step 1 - Remove the Old Continuous Soffit Vent
You should begin to take down the old soffit vent by removing all of the screws which are holding it in place. If you have any screws on the internal part of your vent, then remove them first, and then take out the ones on the soffit itself. Use a drill, and simply put it into reverse in order to extract the screws. Once this has been done, you can then remove the caulk around the edge using the tip of a knife. Scrape away enough to prevent the soffit vent from hanging onto the eaves, and then use your crow bar to pry it off. It is a good idea to have friends to support the weight of the soffit vent as you use the crow bar.
Step 2 - Measure the New Vent
Carefully measure your new continuous soffit vent. Compare the size of the new vent with the hole left by the old one. If there is a significant difference, then you will need to repair this hole. Cut down some lumber, and place it over the hole from the attic side. Nail these boards down until you have covered over the gap. Don't add too much lumber, as this will impede the movement of air from the new vent.
Step 3 - Fit the New Vent
Hold up the new vent against the remaining hole. Screw a screw into each of the corners, until the soffit vent is secure. You can then proceed to screw in the rest of the soffit vent, with holes around every foot, or in the pre-drilled nail holes. If you can use the holes which you had used for the previous vent, so much the better.
Step 4 - Finishing Up
Once you have screwed the vent into position, you can then apply a thick layer of caulk to ensure that it is watertight. If you have added any lumber or similar materials then add caulk to this area, too, to prevent water from pooling in these gaps. When the caulking is done, leave overnight to dry, and then check that the soffit vent is fully watertight.