Bellaire

Second-storey addition over an existing slab

Foundation assessed and reinforced before anything went up, and a new floor set inside the original roofline rather than perched above it.

Property

Single-family ranch

Age

Built 1961

On site

Nine months

Size

980 sq ft added

What was there

Fig. 01 — The original single-storey ranch

A single-storey ranch on a slab-on-grade foundation that had moved, as most in the area have. Differential movement across the width was inside tolerance but not by much, and the slab had never been designed to carry a second floor.

The existing roof was a low-pitch hip, which is the kind of roof a second storey usually destroys.

What the owners wanted

Three bedrooms and a bathroom above, without the house looking like a bungalow wearing a hat.

Stay under the height the deed restrictions allow.

Do not end up with a foundation problem in five years.

Fig. 02 — The addition set inside a raised hip — Bellaire

The design problem

A second storey on a 1961 slab is a foundation question before it is an architectural one. The honest answer was that the slab needed reinforcing regardless of what went on top, and that cost had to sit in the budget before the design was worth developing.

Setting the new floor inside a raised version of the original hip, rather than stacking a box on top, kept the proportions and stayed under the height limit — but it cost usable head height at the perimeter, which the owners had to agree to knowingly.

The build problem

Underpinning and slab reinforcement had to be complete and monitored before any load went on. That put nine weeks of invisible work at the front of a job the owners were impatient to see.

Weather. A second-storey frame in a Gulf Coast summer means the house is open, and the sequence had to allow for it being dried in fast rather than efficiently.

New floor framed, roof geometry set out

What we did

Slab reinforced and underpinned at the load paths, with movement monitored through the frame stage.

New floor set inside a raised hip that follows the original roof geometry, so the house reads as one building.

Perimeter head height traded deliberately for proportion, with the low zones planned as storage rather than left as awkward space.

Bellaire

During the build

Fig. 04 — Underpinning at the load paths

Fig. 05 — New floor framed, roof geometry set out

Materials

Reinforced slab and underpinning
Engineered floor system
Matched hip roof

Worked with

Structural engineer
Geotechnical consultant