The structural work you cannot see, and why it costs the most
The most common reaction to a renovation estimate is that the finishes seem reasonable and the rest seems enormous. That reaction is correct, and it is worth understanding why.
A load path is a chain
Remove a bearing wall and the load it carried has to go somewhere. It goes into a beam. The beam bears on posts. The posts have to be continuous down through the floor framing, blocked so they do not crush the joists beneath them, and they have to land on a footing sized for the load.
If any link in that chain is missing, the failure is gradual and expensive. Drywall cracks at the corners of the opening within a year. Doors on the floor below stop latching. By the time anyone investigates, the finishes above the failure all have to come off.
Footings are the bit nobody budgets for
A footing in an open crawlspace is a day of digging, forms, rebar, an inspection and a pour. The same footing under a finished basement slab means saw cutting, hauling broken concrete out through your house, digging by hand, pouring, and then repouring the slab.
It is the same footing on the drawing and four times the cost in the field. This is why we go into the crawlspace before we price anything.
Shear is the invisible one
Walls do not only carry downward load. They brace the house against lateral force from wind and seismic movement. Put a large opening in an exterior wall and you remove bracing that has to be replaced, usually by re-sheathing adjacent wall sections with structural panel and adding hold-down hardware anchored to the foundation.
On a second-storey addition, the walls below frequently have to be opened from inside and re-sheathed even though nothing about those rooms is changing. Owners find that genuinely hard to accept, and it is not negotiable.
What to do about it
- Get the structural scope priced before you fall in love with a plan
- Ask whether footing access is through open crawlspace or through slab
- Ask whether the design triggers shear re-sheathing, and where
- Spend the money on structure first and phase the finishes if the budget will not carry both
Finishes can be upgraded in ten years. A load path cannot be corrected without removing everything built on top of it.
