Company: WFG
Filing Date: 2025-10-22
Form Type: 6-K
Source: 0001402388-25-000016
Chunk: 0

Company: WEST FRASER TIMBER CO., LTD
Filing Date: 2025-10-22
Form: 6-K
Chunk 0
---
### UNITED STATES

### SECURITIES AND EXCHANGE COMMISSION

#### Washington, D.C. 20549
| FORM 6-K |

### REPORT OF FOREIGN PRIVATE ISSUER

#### PURSUANT TO RULE 13a-16 OR 15d-16

#### UNDER THE SECURITIES EXCHANGE ACT OF 1934

#### For the month of October 2025

#### Commission File Number: 001-39974

#### WEST FRASER TIMBER CO. LTD.
<div align='center'>(Exact name of Registrant, as specified in its charter)</div>

#### 1500 - 885 West Georgia Street

#### Vancouver, British Columbia

#### Canada, V6C 3E8

#### Tel: (604) 895-2700
<div align='center'>(Address and Telephone Number of Registrant's Principal Executive Offices)</div>

Indicate by check mark whether the registrant files or will file annual reports under cover of Form 20-F or Form 40-F.

<div align='center'>Form 20-F ☐ Form 40-F ☒</div>

Indicate by check mark if the registrant is submitting the Form 6-K in paper as permitted by Regulation S-T Rule 101(b)(1): ☐

Indicate by check mark if the registrant is submitting the Form 6-K in paper as permitted by Regulation S-T Rule 101(b)(7): ☐

The information contained in Exhibits 99.1 and 99.2 of this Form 6-K is incorporated by reference into the Registrant’s registration statements on Form S-8: File Nos. 333-257254 and 333-252631.

### EXHIBIT INDEX
| Exhibit 
 99.1    
 99.2    |     | Description                                                                                                                         
 Unaudited Condensed Consolidated Financial Statements for the three and nine months ended September 26, 2025 and September 27, 2024 
 Management's Discussion and Analysis for the three and nine months ended September 26, 2025                                         |
|:--------|:----|:------------------------------------------------------------------------------------------------------------------------------------|
| 99.3    |     | CEO - Certification of Interim Filings                                                                                              |
| 99.4    |     | CFO - Certification of Interim Filings                                                                                              |
| 99.5    |     | News release dated October 22, 2025 re: West Fraser Announces Third Quarter