http://www.findarticles.com/p/articles/mi_m30...
The new Home Depot hardware stores would mean further competition for the independent hardware stores in the United States, as well as Sears' 255 freestanding hardware stores. Including about 70 Orchard Supply units, the Sears hardware stores generated $1.3 billion in sales last year.

http://www.hardwarejournal.com.au/article.asp...
Seven years ago (1996) it made its most aggressive move to rebuild its fading hardlines image by buying Orchard Supply Hardware, at the time a highly successful 61-unit chain of large hardware stores in California.

http://www.doitbestcorp.com/history/home.html
One of the most important facets of HWI's growth in the 1970s was the appearance of the home center. This type of retail store that joined the hardware business to that of the lumber and building supply retailer was unique to HWI from the late 1950s and can trace its lineage to the very beginnings of the company.

http://66.102.7.104/search?q=cache:0_hlxnOUwH..."home+depot"+"home+center"&hl=en
These new stores offer a sense of how fast Home Depot and Lowe's are growing compared to others in this market. The next largest home center, Menard's, Eau Claire, Wis., opened 11 new stores in 2003.
[...]
TOP 10 HOME CENTERS
1. Home Depot, Atlanta
2. Lowe's Companies, Mooresville, N.C.
3. Wal-Mart, Bentonville, Ark.*
4. Sears, Hoffman Estates, Ill.**

I think most people would refer to a "Baumarkt" (e.g. OBI) as a "hardware store". "Home Depot" and "Orchard Supply Hardware"/"OSH" are names of specific hardware store chains in the US (see first two examples).

In the "home improvement industry" the term "home center" is being used for hardware stores with added lumber, garden, etc sections (see examples 3 and 4 above), but I haven't heard anybody talking of making a trip to the home center.

I recommend to wait for feedback from native speakers of English (I am German and have been living in California for the past 11 years).

LEO has

Baumarkt - building center/centre; do-it-yourself store [abbr: DIY store]

Those don't seem exactly wrong to me, though they may all be fairly BE. I do agree that anyone translating for AE should consider other options, since the abbreviation 'DIY' was originally BE and is still probably not familiar to most AE speakers.

However, the unabbreviated 'do-it-yourself' seems to be spreading in the context of home improvement, so it should at least be understandable in AE. 'Building center' also works for me if the context has already been established. (Otherwise it could mean something like a downtown, i.e., a central area with many buildings. I suspect AE more often prefers 'construction' where BE has 'building' in this sense.)

If a superstore is meant, my suggestion would be 'home improvement store,' which gets a lot of web hits, starting with Lowe's and Home Depot, the two US biggies. I agree that such brand names should not be used as generic terms.

'Building-supply store' or 'builders'-supply store' also came to my mind. Those may be more specifically oriented toward professional contractors than do-it-yourselfers, but these days everyone increasingly seems to shop at the same places.

A hardware store to me is smaller, originally the mom-and-pop store on Main Street that sold mostly hand tools and small supplies, as opposed to the lumber store, which was located down by the train tracks or out on the edge of town and sold wood and large supplies. Modern suburban home improvement megastores combine both, plus a lot of other stuff like plumbing and lighting supply, gardening, and so on. But I also agree that 'home center' isn't that idiomatic.

DIY store in England, for example B&Q (http://www.diy.com/), Homebase (http://www.homebase.co.uk/).