Warranties are only good if the contractor is still in business. Structural problems will not show immediately they will start to show as cracks, unlevel surfaces, etc. Also as a structural element there could be a structural collapse. The $500 is cheap relative to the cost of a redo. Have the engineer come out, document and sign/seal as suggested earlier. I would also suggest you get local inspectors looking at the work. Where I live if you don't get permits and it�s noticed you will be asked to pull the permits with the inspector having the right to do a tear down to inspect.

The problem is with the approach. Adding steel at the BOTTOM of the joist THEORETICALLY increases the area moment, ONLY if the steel is jointed intimately to the wood, thereby putting x-section of the steel in pure tension. The problem is that, in practice, joining the steel intimately to the wood is not really doable, no matter how many nails you used. The nails are put in a shear loading, the wood is not stiff enough, and metal just slides on the surface of the wood and never gets put into a tensile load. The better approach would be to install steel on the SIDES of the joist, oriented vertically. The taller the piece of steel, the greater the area moment, and the more it will resist bending ONLY if it is kept from buckling. This is where the wood comes in. Fastening the steel securely to the sides of the wood will keep the steel from buckling, and thereby increase the stiffness of the joist by an amount equivalent toe the area moment of the steel multiplied by the modulus of elasticity of steel, divided by the same for wood. The fastening system works here because the fasteners are put in a tensile load, and very little at that since the steel does not buckle. For example, a wood 2x4 (actually 1.5 x 3.5) has a modulus of around 12.5 and a area moment of around 5.36 inches cubed. Steel strap 3.5 inches wide and only 0.095 inches thick has an area moment of only 0.338 inches cubed, BUT steel has a modulus of around 200. So, if you use the formula for simple deflection, it turns out that steel that is only 0.095 inches thick and 3.5 inches wide is just as stiff as a wood that is the same height, but 2 inches thick. The trick is to keep the steel from buckling, which can be avoided by fastening every few inches with nails, screws, or bolts. The fasteners are under practically no load as long as the steel does not buckle, and of course it will not under such small deflections. Yours truly, S. Lucas Valdes, PEME, Cal Poly, SLO, 1984

Just a follow up: Found a old-time hardware store that had boxes of old "cut thread" tapered wood screws. Flat head not fun to install but job is done and couldn't be any happier. Now measured deflection with a dial indicator under the joists is .030" with a 290lb load walking across it (230lb guy carrying 60lb bucket of joint compound). Forgot to do before and after measurements but walking on it is night and day different.

Transnationalq- we are removing the load bearing wall on the parlor floor to have a large living/dining/kitchen space (open floorplan, for shame!) and are using a series of posts hidden in a powder room and pantry wall, plus one exposed post. Our townhouse is 21' wide, which is too wide to span without the posts. If your rooms are not as wide, you may be able to just use steel footed in the front and back. The other two floors will have posts in the same locations but hidden in bedroom walls (the current load-bearing wall is actually being completely removed, posts added top to bottom and then the walls will be built back in a slightly different space to make for wider hallways.) Our project is a complete gut plus an extension, so the whole thing is costing a fortune but the steel is not a small portion of the project. We likely could have gotten away without steel at all if our span was only 16' or less, but alas...the wide house needs the beam and the concrete footings. I don't have any pics that actually show the sagging in any capacity, but my profile picture shows the stairs which you can sort of see are pitched to the right (towards the center of the house.) We lived in the house with the current state of the floors (stadium seating) and it wasnt the worst, but it was pretty obvious in some rooms. On our top floor, the corner of one room where the rear facade is was about 2 inches higher than the middle of the room. Can't see it in pictures, but it was a very strong slope.