Shifting Clay Soil and Window Fit in East Austin

Four openings, three diagonals each and one tape measure add up to twelve readings before a single sash is ordered, and the intervals austin window replacement fretboard summit uses for checking are longer than a quick measure of width and height. East of the Balcones Fault in Austin, TX the soil is shrink-swell clay, and a window replacement here has to allow for a house that moves a little each season.

How the clay moves a wall

Clay swells when it is wet and shrinks when it dries. Austin gets rain spread through the year, then long dry spells in summer, so the soil under a slab or pier and beam foundation rises and falls. One corner of a house settles while another holds, and the wall framing racks. Openings that were square when built go slightly diamond shaped.

What it does to a window

A racked opening squeezes the frame. A double hung sash begins to bind in its track, a slider drags on its rollers, and a casement that closed cleanly starts to rub at one corner. Glass in a fixed picture window is the weakest part, since it cannot flex, and a hairline crack growing from a corner points to a frame under load.

Measuring before ordering

Measure each opening at the top, middle and bottom for width, and left, center and right for height, and use the smallest number. Check the diagonals with a tape. A difference of more than a quarter inch tells you the opening is out of square and needs shimming or a wider gap for foam. A level on the sill shows whether it slopes toward the room.

Installing for a moving house

The installer should leave a gap between the frame and the rough opening and fill it with low expansion foam, not stuff it tight. Shims go at the hinge points and under the sill, never at random. The sealant should be a flexible type rated for movement so the joint can stretch and return. A vinyl window frame that floats on a nail fin tolerates small shifts better than a rigid frame screwed through at every point.

Foundation first

If the same openings keep binding, the problem is under the house. Gaps at the top of interior door frames, diagonal cracks in drywall corners, and brick separating near Hyde Park or Tarrytown all suggest the foundation should be looked at before new windows go in. Limestone hills west of the Balcones Escarpment have thinner soil and behave differently, so a house there may sit on rock more than clay. A new window cannot fix a moving wall, but a good installation will not make the movement worse.