<Page>
--------------------------------------------------------------------------------
SECURITIES AND EXCHANGE COMMISSION
WASHINGTON, D.C. 20549
------------------------
FORM 8-K
CURRENT REPORT
PURSUANT TO SECTION 13 OR 15(d)
OF THE SECURITIES EXCHANGE ACT OF 1934
DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED): SEPTEMBER 20, 2001
------------------------
ATRIUM COMPANIES, INC.
(Exact name of Registrant as specified in its charter)
DELAWARE 333-20095 75-2642488
(State or other (Commission File Number) (I.R.S. Employer
jurisdiction of incorporation) Identification Number)
1341 W. MOCKINGBIRD LANE
SUITE 1200W 75247
DALLAS, TEXAS (Zip code)
(Address of principal
executive offices)
Registrant's telephone number, including area code: (214) 630-5757
N/A
(former address if changed since last report)
--------------------------------------------------------------------------------
<Page>
INFORMATION TO BE INCLUDED IN THE REPORT
ITEM 2. ACQUISITION OR DISPOSITION OF ASSETS
Royal Group Technologies Limited (RYG: TSE, NYSE) has entered into agreements
with Atrium Companies Inc. to acquire the extrusion assets of Atrium's
subsidiary, Thermal Industries, Inc. located in Pittsburgh, Pennsylvania and
to supply extruded profiles to Thermal Industries' fabricating operations.
Under the terms of the supply agreement, Royal will supply approximately $7
million per year of extruded profiles to Thermal's fabrication plants located
in Pennsylvania. The term of the supply agreement is for a period expiring
December 31, 2006.
The extrusion assets, being acquired for $3.8 million, will be relocated to
various Royal Group custom profile manufacturing plants located in the United
States and Canada. The relocation of extrusion assets will commence October 1,
2001 and is expected to be completed by December 31, 2001, with supply of
extrusions commencing as certain of the purchased assets are made operational.
ITEM 7. FINANCIAL STATEMENTS AND EXHIBITS
(a) EXHIBITS
*99.1 Press Release of Royal Group and Atrium Companies, Inc. dated September
20, 2001.
----------------
*Filed herewith
<Page>
SIGNATURES
Pursuant to the requirements of the Securities Exchange Act of 1934, the
registrant has duly caused this report to be signed on its behalf by the
undersigned thereunto duly authorized.
ATRIUM COMPANIES, INC.
By: /s/ Jeff L. Hull
----------------
Name: Jeff L. Hull
Title: President and CEO
Date: September 21, 2001
<Page>
INDEX TO EXHIBITS
<Table>
<Caption>
EXHIBITS
NUMBER
--------
*99.1 Press Release of Royal Group and Atrium Companies, Inc. dated
September 20, 2001.
</Table>
----------------
*Filed herewith