Home>Discussions>ELECTRICAL & LIGHTING>How to repair roof trusses bored for electrical wiring?
11 posts / 0 new
Last post
gigi_marga
How to repair roof trusses bored for electrical wiring?

The roof in my garage was made with manufactured trusses constructed with 2 by 4 lumber and spanning 24 feet. Although the attic does not have any construction (any living space nor storage), and there is plenty of room to pass wires, the constructor decided to bore 3/4" holes through each of the trusses within millimeters of one of the lower end corners in the lower chord next to the metal connecting plates. Some holes where drilled slightly at an angle removing even more wood than a straight hole will do.

While the roof survived many years, every time I pass through the garage I feel I need to do something about the situation, even more so considering the increased storm activity in recent years.

I already rerouted the wires and I would like to reinforce the trusses to at least their original strength but I am not sure how to do it.

Please advise.

What makes the situation even worse is that my house is the first house ever build (his own house) by the creator of one of the most enduring home improvement TV shows, now airing next to "This old house" on Create TV. I really trusted I would benefit from the expertise and I was deeply disappointed having found countless examples of poor craftsmanship that have eaten away the last five years of my life fixing the place. This is one of the very last problems and I really don't know how to tackle the situation.

Please help.

canuk
Re: How to repair roof trusses bored for electrical wiring?

If I'm reading your description correctly -- where the bottom and top cord meet and joined with a connection plate is known as the heel.

Normally it's never allowed to bore holes or notch engineered framing components without approval from the manufacturer.
By the way --- running plumbing ranks number 1 for damage to framing with electrical being number 2.

If the bored holes are within the bearing point ( typically where the heel sits on the wall top plate ) there shouldn't be much concern. If the bored holes are not within but just outside ( or inside ) the bearing points and given the smaller size then it may not be much of a concern either --- depending on snow load conditions.

In this case I would think a 2X4 about 24 inches in length sistered onto the bottom cord so one end rests on the bearing point and extending outward ( or inward depending on how you look at it ) would suffice. An alternative would be attach 3/4 inch plywood in the same dimension ( glued and screwed ) on both sides of the bottom cord .
Either way should give you the peace of mind you need.

Gizmo
Re: How to repair roof trusses bored for electrical wiring?

Drilling through any engineered truss is a no,no...a (Cardinal Sin). In your case I really dont think you will ever have any structual problems unless you decide to use the attic area for living space or storage that will have a ton of weight on the ceiling cords.

dj1
Re: How to repair roof trusses bored for electrical wiring?

canuk,

Wouldn't running full length (from heel to ridge) sister rafters be a better and stronger solution?

Sombreuil_mongrel
Re: How to repair roof trusses bored for electrical wiring?

You repair it with a piece of paper called a "structural engineer's mitigation plan"; nothing else is accepted by the JHA.
Casey

Cougars1996
Re: How to repair roof trusses bored for electrical wiring?

Our modular had 2x4 trusses with 2x3 bottom chords. When we gutted the bathroom for renovation we found that one of the bottom chords had cracked and that is what caused the ceiling sheetrock to crack.

My solution, which has gone well for a year without anymore problems (knock on wood) was to sister a 2x4 to the side of each bottom chord. I used a good construction adhesive and screws and ran the 2x4 from the exterior wall to the house center wall (both load bearing) in the bathroom. In the end, this was the easiest, gave the most strength, and added additional surface for screwing sheetrock to.

I would do this if you have access to the whole space.

Good luck!!

canuk
Re: How to repair roof trusses bored for electrical wiring?
dj1 wrote:

canuk,

Wouldn't running full length (from heel to ridge) sister rafters be a better and stronger solution?

You could but that's overkill.
You could simply get away with a plywood gusset at the heel joint.
It's only a 3/4 inch bored hole.

WitchDoctor
Re: How to repair roof trusses bored for electrical wiring?
canuk wrote:

You could but that's overkill.
You could simply get away with a plywood gusset at the heel joint.
It's only a 3/4 inch bored hole.

A little common sense is a good thing ...;)

Nestor
Re: How to repair roof trusses bored for electrical wiring?

If these were my trusses, I'd:

1. Apply duct tape to both sides of the truss hole, but notch the tape on one side so that the nozzle of a caulking gun can be inserted into the hole.

2. Fill each hole with LePage's PL Premium construction adhesive.

3. Use a clamp to sandwich the hole between two small flat boards, thereby forcing any excess adhesive out the notch hole and keeping the adhesive flush with the sides of the truss.

4. Allow a day or two for the construction adhesive to cure sufficiently to remove the clamp and pull the duct tape off.

PL Premium will form a bond with wood that's stronger than wood.

Cured PL Premium is about as strong and hard as wood.

Since these holes are in a location where they don't weaken the truss very much anyhow, simply filling the holes with PL Premium would go most of the way (at least) in repairing the trusses.

jkirk
Re: How to repair roof trusses bored for electrical wiring?

almost all engineers will want a 3/4" plywood gusset glued and screwed both sides to repair the truss, it will strenghthen the portion drilled and lock everything together that much more where the damage was done

as for the electrician who drilled the truss, i hope to god it was a 1st yr apprentice other wise a real electrician would know better. the guys that never seem to amaze me when it comes to doing something stupid like this are hvac installers. they dont care what they cut or drill

Fencepost
Re: How to repair roof trusses bored for electrical wiring?

You could also make some drawings of the trusses showing rough dimensions and the location of the hole, then go to a local truss manufacturer and ask them their advice. Since every truss is supposed to be stamped by the manufacturer, you should be able to go to them. They may even have records for your particular house.

Since every truss manufacturer has a designer/engineer either on staff or available, you may be able to get solid advice for free or reasonable cost.

Sponsored Stories

TV Listings

Find TV listings for This Old House and Ask This Old House in your area.