Home Plans And Home Designs - 2x4 for joists?!

My house has a one story addition built in the 60’s or 70’s that’s a dining room/ garage on a slab. The entire unit is about 700 sq. ft (33 x 21).

The roof is supported by a truss.(http://biytoday.com/roofTrusses2.jpg See “Extended Tie”).
The joists running across the attic floor are 2x4’s spaced 16 inches on center…running the full 21 feet.

Is this safe? Was this considered to be up to code at the time? Is it safe to walk up there?

I don’t know much about structure but how is a 21 foot 2x4 able to support the roof, ceiling, my weight when walking in the attic, etc? There are no support columns or support beams under any of the 2x4’s.
I’d have expected at least 2x6’s if not more.

Hi there,

I'd assume that is the same house we discussed?
http://forum.doityourself.com/general-law-legal-advice/403700-new-home-without-permits.html#post1627792

As I stated previously, you should follow the specifications of the building permits. If the house was built following a BP, then you can be sure that it is safe
If you have not a permit and if you are not an civil engineer, I'd suggest to contact the building department, get the house inspected and get a building permit

Certainly, trusses and structuures are not a DIY job

Hi HG, you are fortunate that you looked. There are trusses I would not walk on. Even if they won't break, your chances of popping some nails/screws is high. I'm not sure if design standards have changed or not, but trusses can often push the limit of ones imagination :).

If you have to work up there, consider some boards spanning many joists.

Bud

If you have not a permit and if you are not an civil engineer, I'd suggest to contact the building department, get the house inspected and get a building permit


A permit was taken out for this job however, there is no confirmation that I was inspected as records previous to 1980-something were migrated over to a newer administrative system. So, I don't know if it's valid.

Would I get the building department to inspect it or an independent third party?




If you have to work up there, consider some boards spanning many joists.

Bud

Yes, I already have plywood across the joists. I'll refrain from storing heavy items up there at least.

Just for general information, as already stated by the others, manufactured trusses aren't built to hold a load from above. They barely can hold up sheetrock, although they are engineered to do so. So be careful with the long span.

I will agree with the other posters that said that the 2 x 4 truss was only designed to hold the roof up and the ceiling up.

There is too much span and too much movement for them to be used to hold any significant amount of weight - especially someone walking on them.

I have a cousin that has what we call a Patwell home - they were a home manufacturer that threw up a lot of cheap houses back in the 70's.

My cousin was in the attic for what ever reason and he slipped and stepped on one truss and put all his weight on that truss and it broke. There is a big gouge in his livingroom ceiling from where the drywall broke.

My suggestion to you is to take down the ceiling in one room where it will give you access to the attic and then sister 2 x 8's to the 2 x 4's and then put the plywood back into the attic.

It might take you a whole month to do it right, but at least you will know that it was done right.

I would also pay careful attention to how I supported those 2 x 8's at the edge of the walls.

Newtons law - what goes up - must come down.

If you have a fire or a earthquake or a tornado - where do you think all that heavy stuff in the attic is going to go?

Down on your head!

They barely can hold up sheetrock, although they are engineered to do so.
What’s irritating is it was built with pull down attic stairs, thus inviting any lay person to walk around up there and encouraging them to store materials. I can’t imagine how an inspector allowed this.


My suggestion to you is to take down the ceiling in one room where it will give you access to the attic and then sister 2 x 8's to the 2 x 4's and then put the plywood back into the attic.

There is a single 2x4 on top of all the joists running perpendicular. When I eye-ball it, there is a slight depression of about one or two inches. Is this just normal settling?

If your trusses were supplied by a reputable truss manufacturer, then they were also designed by a licensed structural engineer. Also assuming they were handled properly and set properly, then I would say what you have is OK. Please note that trusses are not designed to take any kind of storage unless they were specifically designed to do so; if I remember my "Basic Truss 101", the bottom chord is designed to support a ceiling and insulation to a maximum of something like 5 or 10 PSF. If someone put in one of those pull-down attic stairs and the truss was not designed for attic storage, well... Certainly not something I would do.

I would also not waste my time looking to see if the inspector at the time inspected the trusses. Inspectors cannot look at a truss and tell if it was designed properly. It's an engineered product, all they would be interested in is if it was designed by a licensed engineer or if it had obvious signs of mishandling that weakened it. If an inspector looked at it now, probably the best he could do is say something doesn't look right, you need an engineer.

Finally, I would be very cautious about attaching anything directly to the trusses. When you do, you change how the forces work on the truss. If it were me, I would keep any additional framing completely independent of the trusses. I don't know what you want to do in the attic, but 21' is a REALLY long span for even a 2x8; in fact, can you even GET a 22' 2x8??

In fact, the more I think about it, the more I think it would be in your best interest to bite the bullet and hire a structural engineer to look at everything. It might cost you a few hundred dollars, but it would be cheaper than guessing about something based on what I or someone else is also guessing, and then be wrong.

Hi Bruce,

Just a note regarding my comment about the inspections--> it is related with the post I linked

Just a few more comments on trusses:

The company I work for manufacturers roof & floor truss. Bruce is entirely correct when cautioning against sistering to an existing truss. It WILL modify the engineered characteristics of the truss and may make it less safe - not more.

Roof trusses can be engineered and built to carry storage loads, even room additions, but the bottom chord is always more than a 2X4 - sometimes as heavy as a 2X10 for attic rooms.

A structural engineer (as suggested) is the only way to know for sure the limits on storage in your attic.

BTW Bruce, 22' 2X8's in Pine are available in my area. Same should be true of Doug & Hem Fir out west.