In 1927, the roof of the White House was raised and a third floor inserted where the attic had been. The terra cotta blocks in the picture look like products from the 1920s and probably were installed in 1927. Although the White House likely was weakened by various alterations over the years (e.g., cutting through beams for plumbing and wiring, moving a load bearing wall to enlarge the State Dining Room in 1902), I have read that the added weight of the 1927 third floor addition probably was the straw that broke the camel's back.

I remember reading somewhere the explanation that by this time "the floors were holding up simply out of habit!"

Indeed! One of my all-time favorite Weekly Reader stories back in the 60's was on the renovation of the White House. One particularly fascinating picture showed a part of the interior that had been gutted down to the sandstone walls and a front end loader driving around inside.

I've never seen those types of terra cotta blocks used for ceiling construction. My neighbor has a garage with walls built of those. I can't imagine building long horizontal expanses such as a ceiling with them. Surely they wrap structural beams of some sort and serve the purpose of insulation, more than anything. I'd certainly hope they aren't in any way load-bearing, and surely would not want to be under them during an earthquake.

Before this renovation, the White House was still the building, to all intents and purposes, built in the 1790s, prior to gassification, running water, electrification, telegraphy, telephony, radio, interior kitchens becoming normal, modern building reinforcement, etc. As such the White House was stone and wood, with patchwork upgrades (well done, but patchwork nevertheless) to add features for the convienence of the President. However, it was still an essentially a building that had been built with wood using 18th century construction and had been continuously occupied and used for about 130 years; maintenence of key areas had never been able to be performed.

Bess Truman played the piano, and so they had a piano brought into what is is now the "Formal Family Dining Room" (there are four dining rooms the First Family uses; that one, also called the Prince of Wales room, is used for intimate, but not private, meals, and is the second most public). The floor, however, eventually gave out while Harry was playing. Harry used that as an excuse to strong-arm Congress (which had just canceled the then-planned West Wing expansion due to cost) to rebuild the entire White House except the East Wing.

Here is a link to see some history of this specific room.

Considering the date, the U.S. was in the beginning stages of the post WW2 cold war, with the fear of nuclear annihilation all around us.

Given the fact that they were adding "steel shoring columns", this begs the question of whether this was just a simple renovation, or an attempt to better protect the President in case of nuclear attack.

[The interior of the building was on the verge of collapse. - tterrace]