Can I modify attic trusses for storage or do they have to be replaced?

It is illegal to modify an engineered product with out having it evaluated by a structural engineer. Furthermore any approved alterations by said engineer will require a permit from the local building department. Failure to obtain the necessary paperwork could be catastrophic. If you alter the trusses and they fail and someone is injured you will be in a mess of legal trouble.

If you can't afford to do this properly then how do you plan on affording the repairs, potential fines and judgments. Not to mention someone may notice what you are doing (like maybe a contractor working in the area who see's structural materials and no permits) and turn you in to the building department. This could result in a stop work order, temporary condemnation of the structure, daily fines for failure to comply with building ordinances, increased engineering fees to fix errors that may not have occurred otherwise, and so on. If you don't think it can happen let me assure that I have made such reports to the building department when working on jobs and know other contractors who have as well as nosy neighbors and HOA's.

Last but not least the fact that you had to ask this question means you are not qualified to do the modification. If you lack the knowledge, tools, and ability to do the work you will most likely spend more than if you saved the money and paid someone who does.

We have modified regular trusses and created rooms in them.

First look for a residential architectural company and call them and explain the situation. Usually they either have an engineering degree or know a friend who does.

Explain what your budget is and possibly (to save them some time) e-mail them some pictures of the existing trusses using a good cell phone camera.

I can tell you what we had to do:

We installed a temporary wall under the center of the existing trusses bottom cord.

We than had to run 2" x 8" boards along and up against 1 side of the bottom cord of the existing trusses. The 2" x 8"s had to extend 4' past the width of the room above on each side. So a 12' room above required 20' pcs. of 2" x 8". We then had to install an upright laminated 2" x 8" along the ends of these new 2" x 8" bottom cords and then use joist straps to go around the existing bottom truss cord and the new 2" x 8" board. Remember you are resting the 2" x 8" laminated beam sits on top of the end of the new 2" x 8" sister joists. The joist straps slide under and attach to the flat side of the laminated beam. We used heavy gauge rolls of 1+1/2" hvac strapping pulling them up tight with vise grips and then screwing them into the beam.

You also then have to install a vertical pc. on every truss from the side of the bottom cord up to the top angle cut of the top cord. This runs plumb and you screw it into any web truss cords that it crosses. Snap lines to keep these all straight as this is your wall line also. Do this on both sides of your new room. These go on the opposite sides of where you put your new floor joist *2" x8". The last thing we had to do was to run a 2 " x 6" along side the top cord from the ridge peak down 4' past the new vertical boards you just installed. Glue and screw into the existing truss top cord. This goes on the other side of the truss so you don't hit the vertical board at the end.

Now just make sure you do not drill any holes for wiring,plumbing in any of the trusses or the new boards you installed. Figure about $28 per truss for lumber and add $ for some tubes of H.D. Liquid nails.

Now cut out the truss webbing to open up your new roof. Then take down the temporary wall under the trusses. This was designed by structural engineer , but it may not meet code in your area. Roof pitch was 9/12

Room In Attic Truss

M G, Most all the answers here are to me- very good information needed to answer your question properly. I`ve done many jobs like this in the past and not to repeat these other answers again, You need to have the modification's engineered and stamped for approval before starting this big project. All trusses are engineered to carry the roof loads(live,dead,snow,etc.) for your area. Modifications can be done-(Yes), "if'" they are "engineered". You should have a set of your house blueprints. Take them to a local engineer and have he/she look at them and see if this project can be done within your budget. This 'first' step will get you closer to seeing if you can do this project. If so, he/she can "design" what your looking for. Give all the info. to this engineer and explain what direction you want to go. Having good experienced carpenters in your family is a big plus for you here. That should bring peace to your mind, but they probably already told you what needs to be done. You don`t need to take anything to a designer, take the blueprints back to the one who drew them up. Hoped this helped make this big decision less stressful. Good Luck...

It can be done with the proper modifications to the existing trusses. This will include adding supports and may require additional stiffening of the beams. You really need to have the engineer review you existing set-up and make the required calculations for the modifications you want to make.

I don't have an attic. I have a basement. I actually live in my basement. We don't use it for storage. I live in an American town house. A basement is kind of like an attic except its below the house, not above it. They're useful for tornadoes because basements are underground.