Blocking and leveling
Frame piers must sit within 24 inches of each end and no more than 120 inches apart under the main rails (24 CFR 3285.310).
Piers and leveling
At least 12 inches of clearance is required between the lowest frame member and the ground.
Frame piers under 36 inches may be single stacks of 8 by 8 by 16 inch concrete blocks within their design capacity.
Mortar is not required for block piers unless the instructions or an engineer call for it.
Footings must reach below the frost line unless designed for placement above it.
The site must drain away from the home at least one half inch per foot for the first ten feet.
TDHCA suggests testing every door after move-in, since sticking doors can mean the home is not level.
Sources: Pier spacing; Clearance under the home; Concrete block piers; Drainage; Doors as a level check
Relevel after a move
In Texas, releveling counts as installation work: only a licensed installer may install, relevel or modify the foundation.
Frost and footings
TDHCA lists 42 Texas counties, from Armstrong to Wilbarger, with a 12 inch frost line depth to consider when installing a new home.
In those counties, footings go below the frost line unless an engineer or architect designs an insulated foundation or a monolithic slab for the site.
Footings can be 4 inch precast concrete pads, 6 inch poured concrete pads or ribbons, pressure treated wood built to the rule, or listed ABS pads certified for the site's soil.
When the local authority cannot give a frost line depth, a registered engineer, architect or geologist must set it for the site.
Pier spacing
Frame piers go no more than 24 inches from both ends of the home and no more than 120 inches apart, center to center, under the main rails.
Source: 24 CFR 3285.310
Pier heights
Frame piers from 36 to 67 inches high, and corner piers over three blocks high, must be double, interlocked concrete blocks.
Piers over 67 inches high must be designed by a registered professional engineer or architect.
A short pier may lean no more than one half inch from top to bottom, and a 36 to 67 inch pier no more than one inch.
Source: 24 CFR 3285.306
Caps, shims and gaps
Pier caps must be solid concrete or masonry at least 4 inches thick, hardboard lumber at least 2 inches, or corrosion protected steel at least one half inch, the same size as the pier.
Gaps between the chassis beam and the pier cap are filled with 4 by 6 by 1 inch shims used in pairs and driven tight, taking up no more than one inch.
On manufactured steel piers, the adjustable riser may extend no more than 2 inches when finally set.
Source: 24 CFR 3285.304
Common questions
What is blocking and leveling?
Frame piers must sit within 24 inches of each end and no more than 120 inches apart under the main rails (24 CFR 3285.310).