How to Run Plumbing Pipes under Joists

What You'll Need
Foam Insulation

When you are plumbing pipes, you may find that you need to trail the pipes under the joists of your house. Some plumbers consider it perfectly alright to fit the pipes through the joists, and many people with older houses will see evidence of this practice, but if you want to put your pipes under the joists, so that they can carry water, or sewage, to and from the home, then you will need to work out how you can fit your pipes without damaging the structure of your home. You can easily create a support for your pipes without penetrating the joists by following these guidelines, and with a few simple household tools you should be able to fit your pipes around your architecture easily.

Step 1 - Fit the Pipes

Fit the pipes around the joists as though you were plumbing the pipes around any other part of the home. You may need a few joint pieces in order to keep the pipes in line, but you should not have too much trouble fitting the pipes into place. Use a wrench or screwdriver to tighten the pipe fittings around the edges of your pipes, and make sure that the entire system is leak free before you proceed to any of the other steps. Run water through the pipes as often as you need to in order to ensure that you are completely dry on the outside of the pipes.

Step 2 - Build an Enclosure

In order to support the pipes in their place, you will need to build yourself an enclosure. These parts of the pipe around the joists will be covered with a layer of wood which will hold them in place, prevent them from jutting out and being a nuisance, and keep them safe from other damage. Lay your wood out, and saw to fit the area around the joists if necessary. Install the first piece against the wall using brackets and screws, and then fit the rest of the wood around it until you have a completely sealed box. Make sure that the outside of the box is covered in a waterproof sealant such as caulking, except for a small area at the top.

Step 3 - Add Foam

You will now need to use a foam insulation in order to protect the pipes. Press the nozzle into the gap which you left in the top of the enclosure, and squeeze the foam into it until it breaks through the surface and you can see that the enclosure is full. Allow the foam to harden, and then use the insulation again to ensure that everything is filled with the foam. You should then seal over the edge of the enclosure using a piece of duct tape, and sealing that into the surrounding structure using more caulking.