Methodology
Last updated November 9, 2026
Every number on this site is either sourced or labelled as an estimate. This page explains the difference, and how a claim gets from a source document to a published page.
1. Primary sources first
Structural claims follow the locally adopted building code and the engineer's stamped plan, not a manufacturer's marketing. For segmental walls we use the block and geogrid manufacturer's published design tables and installation manual. For drainage we use the same code sections the inspector cites. For permitting we use the local building department named on the city page.
2. Cost models show their inputs
Installed cost is modelled from visible inputs: the material or equipment price, the labour and access scope (excavation, drain, electrical, permit), consumables, and a reserve for service or repair. We do not present a single "average cost" as if it were a quote; the range and what it includes are stated on the page.
3. How options are compared
We compare systems on retained height per course or lift, reinforcement requirement, drainage detail, service life and maintenance. A system earns a recommendation for a stated height, soil and surcharge; no supplier can buy a place in a comparison.
4. What we have not tested
We do not run a laboratory or a crew, and we do not carry out every job we write about. When a claim comes from a manufacturer document, an adopted code, a certification listing or a contractor report, we say which. We do not imply first-hand testing we did not perform.
5. Sources we work from
| Source type | What it decides | How it is cited |
|---|---|---|
| Adopted building code and local amendments | When a permit and stamped engineering are required | Section cited |
| Manufacturer design tables and installation manuals | Block capacity, geogrid length and placement | Table reproduced with the product named |
| Engineer-of-record plans | Site-specific design and surcharge assumptions | Plan referenced, not reproduced |
| Local building departments | Permit scope, inspection stages and fees | Office named, with its link |
| Published US price guides | Installed cost bands | Band with the month it was checked |
When two sources disagree, the page says which one it followed and why. A figure that cannot be traced to a document is labelled an estimate, and an estimate is never presented as the price of a specific job.
6. Listings and directory data
The service-area directory is compiled from public business records: the firm's own website, its published address and phone number, and the state or local licence register named on the city page. A record is marked verified only when the name, address, phone and licence have been checked against those sources and the date of the check recorded; everything else is labelled. Where a source does not publish a ZIP code or a website, the field is left blank rather than guessed.
7. Corrections
If a code, a specification or a listing changes, we update the article and its "last updated" date. Emailcontact@retainingwalllab.com with the page and the correction.