Placing too much stress on ceiling?

[Don Morris]

When we renovated our home, we added about 100 sq ft to the size of a family room which sat to the side of the home by extending it. it is very long and narrow. Now it's just more long and narrow, but with more light because of 5 side by side windows added with the extension. The roof line was just made higher by adding a new roof over the old roof. There is about 6' of head room at the highest point in the new roof over the old roof. I thought "Oh boy, more storage area". Well, putting things on the old roof is a PITA because it's at the slant of a roof. Everything wants to slide down/or tip over, even though the shingles have some gripping power. When I put things on the shingles of the old roof, I wasn't concerned about the old roof taking the weight of what I put on it. There wasn't anything under it. In looking around for a flat area to place things, one possible solution I can come up with is to put shelving on the vertical supports that run from the base area to the rafters of the new roof. That way I could put things on shelving and not have to worry about them tipping over as has happened when I put things on the old roof. However, there is a ceiling under the base of those vertical supports. I really don't want to have ceiling cracks because I put too much weight on the vertical supports. Does that look like it might happen if I did? In one photo you can see the side of the old roof line through the entrance door from the main part of the home. The other photos are the exterior view of the addition, the ceiling below the attic area in question and the vertical 2 x 4's supporting the rafters on the new roof. I could design a horizontal shelving system off those vertical struts without difficulty, but...is that a good idea? Thanks for your thoughts.

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Don M

[Lee Schierer]

What size are the ceiling joists. What is their spacing? Which way do they run and how long is the span? That Knee wall looks like it was intended to square off the space for dry wall, nit for holding up the roof or supporting a load of any kind. All the weight is going to be transferred to the ceiling joists, so you need to determine their load capacity.

[Alan Caro]

Don Morris,

It's impossible to predict the kind of deflection that the added loads of the storage structure and of course, the weight of objects stored there might induce. My concern is more that the ridge of the new roof will sag with the vertical point loads of the vertical, i.e. hanging attic floor supports. It's possible the old roof structure will transfer the load to the outside walls and protect the new ceiling, but without seeing more of the details, the preferred solution in my view, would be to intersperse and nail 2 X 8 shaped blocks next to each of the sloping roof joists over the portion of the volume intended for storage, if possible so they might extend to bear on the top plate of the wall. Then, run (level) 2 X 8's as floor joists that bear on the new shaped blocks and are nailed into the rood joists over the intended area and add a 3/4" plywood floor. The blocks strengthen the lower portion of the roof joists- reduce bending- and transfer the load to the walls. As the new floor joists are attached near the base of the roof joists, they will act as roof ties to maintain the level roof ridge and the floor will also disperse unequal loads over more of the joists, are by their lower position, more directly transferring the load to the vertical walls. In fact the new storage floor structure could do a lot to make the long, narrow structure much more rigid by acting as a diaphragm. Long, narrow structures that are also quite tall- as I imagine this may be the case here because of the original roof structure is adding height, and this is a recipe for what in structural is termed "floppy".

I am a bit over-cautious in this way after thirty years of design houses in seismic zones in California.You're wise to consider the situation carefully. A typical floor design weight is 46 lbs. /sq. ft. and 2 x 4's unless short and close are not terribly good at it. It's possible that the floor joists could be 2 X 6, depending on the length and spacing and you can obtain that information using a Type V sheet from the local Building and Safety (and they may be posted online).

Looks like a very nicely done remodel / extension- good job.

Alan Caro