How to Feed Cable Through Insulated Walls
It's not as hard as you think. Here are a few handy techniques.
Drilling up or down and fishing cable through insulated walls is an inconvenience, but nothing more.
Sure, there are certain techniques you can't use through insulation, but there are always work-arounds.
What Are Insulated Walls?
What exactly are insulated walls? They:
- are mainly wall cavities filled with fiberglass batt insulation
- were used in nearly all homes starting in the early 1960s, usually in outside walls or in walls that divided "conditioned space" from unconditioned space
- are almost always associated with applications where in Sheetrock is used as the interior wall covering
This stuff is usually no problem; it just makes a mess when you make a decent-sized opening in the wall. You will often find it has all settled to the bottom of the wall.
Some newer homes have expanded foam in the walls. This is not impossible to deal with, but difficult.
Where to Drill
Regardless of whether you're drilling up or down in an insulated wall -- from an opening in the wall or into the wall cavity from above (through top plate) or from below (through sole plate) -- the place you want to aim for with the bit is in the corner of the wall cavity.
If you're drilling up from an opening you've made for an outlet or speaker in the Sheetrock:
- push the bit through the insulation, using short jabs, at an upward angle, toward either back corner
- if there is paper, foil or plastic on your side, just cut through it
- when the bit hits the back corner, walk the bit into and up the corner by giving the drill short bursts (forward or reverse, whichever works better)
If you're drilling down into a basement or crawl space from an outlet opening near the floor, use your drill guide to keep the bit in front of the insulation and aim it into one of the front corners.
If you're drilling into the wall cavity from above or below:
- try to make the hole near one of the corners. Sometimes the best corner to use depends on the insulation
- if there is no foil or paper backing, it doesn't matter much
- if the insulation has a foil or paper backing, then it may have been installed by stapling the paper/foil to the inside of the studs (see here).
If the insulation was stapled to the outside of the studs, then there is usually a nice open space in the center of the wall cavity. This makes fishing the cable up/down much easier.