Can roof trusses support a 40 hot water heater?

Hello All,

Based on my knowledge of roof trusses they can only support about 250 lbs. They should not be altered unless redesigned by a structural engineer. Last, not suppose to store anything on them.

Just left a home inspection with 2x4 trusses holding up a 40 gallon hotwater heater, gallon of water is 8 lbs x 40 gallons = 320 lbs + the weight of the water heater.

In addition, gas furnace was installed, one truss was in the way, it was cut, no additional bracing.

Can this be done?

Any and all input welcome.

Thank you,



Sure, anything can be done!! Is it right? No. This kinda stuff keeps us employed! But never, never ask if it can be done, because we all know anything can and will be done, right or wrong.

I also see you are in New Hampshire. Gets a bit nippy there, no? A water heater in the attic probably isn’t the best idea.

Looks like the water heater is sitting between the trusses. Need to know what’s going on below. My guess is there is a load bearing wall supporting the water heater. I’ve never liked an attic location for a water heater, but I do see it here from time to time.

I’d like to know why a W/H is situated in the attic in the first place.

Frozen pipes are imminent…

Hi Steve,
I think answer lies in what is supporting the “floor” that the water heater is sitting on. I also think water heater in attic is crazy in cold climates (assuming it is unconditioned space). If this is a cold attic I would warn client about risk of freezing and heat loss.

Steve, obviously a cut truss to allow furnace install is incorrect. I don’t see any insulation? Also furnace and hot water heater produce heat that can add heat to the attic in winter months…seen a lot of snow melt and associated ice dam formation with this kind of set up. Increases need for proper attic ventilation in my opinion. Would this be some type of camp or 3 season property that is now converted to year round use?

Doesn’t say where he is located, and I would be curious as to where he got the 250# capacity for a wood truss.

Also this one shows a flooring on the bottom of the truss,. Was that truss designed for the furnace and water heater and additional storage?

Mark, Flooring consists of loose planks across 2x4s.

Marcel, With regards to 250lbs weight load, read it someplace on roof truss lower chord could only support 250 lbs due to gusset plate failure and strength of 2x4. Also quick call to a structural engineer said they are not designed to support weight loads within the framing members.

Joshua, I agree, it’s not correct. However, I heard the usual comment from the sellers realtor “well it been like that for 45 years”. I calmly explained even though it hasn’t fallen through the ceiling does not make it correct.

I didn’t state this but thought it, if I don’t call it out, the client may have legal recourse at me for not doing so.

The other issue I failed to mention is the attic is loaded with mildew(can’t call it mold because I didn’t test it). Not surprised because there is an gas open flame furnace and a gas hot water heater warming up what should be a cold attic space.

I explained to the client what 1 bathroom fan can do to an attic space. Therefore, not surprised these two items have caused that problem.

Bottom line, should not be there, unless a structural engineer redesigns the trusses to handle the load.

Found this, note what it says about any alterations.

Thanks for the feedback.




Trusses can be designed to support any load.

If the bottom chord is 2X4, it has not been designed to support any additional load other than the roof-structure.

What about freezing pipes/tanks/components in the “balmy” New Hampshire winters? Did they say anything about problems associated with that?

Jeffrey, My point exactly, bottom cord 2x4 is not designed to support a load. Granted it’s up against the house wall, but should not of been done.

Joshua, appears the heat generated from the hot water heater and the furnace keep the attic nice and warm.

As I mentioned, 75% of the attic space is covered with active mildew 23%+.

Thanks for the comments,


The question is what is underneath the truss helping to support the tank if anything. Truss span, local snow loads, pitch of roof, type of lumber used to manufacture the trusses, truss plate sizing. Assume a dead load of TC and BC at 10lbs/sqft. In short this sort of thing needs a quick look and some calculations of a structural engineer, heat loss and pipe freezing concerns aside.

As mentioned above there is no “maximum” load that a truss can handle. Trusses can be designed for any dead/live load combination.

For a quick and dirty on the forces involved in a truss take a look at this link:

Sure, but I don’t see a hot water heater in this photo because it does not exist. It’s a water heater!