Home Depot's investment in boring but necessary renovations is paying off.The home improvement chain is catching up with Walmart in market capitalization, at $310 billion.Both are benefiting from the effects of Covid, but the largest DIY supplier in the US has a few more tools in the box.Walmart is up a respectable 14% this year, making it worth more than $380 billion.That's because it's well placed to supply the star products of the lockdown.However, Home Depot has bounced higher.It's up more than 30% in 2020, as is smaller rival Lowe's.Also, a year ago, Home Depot was far behind Walmart in price/earnings ratio.Not only has the gap closed, but investors give Home Depot a slight edge, estimating it to be worth 29 times historical earnings, versus Walmart's 26.Home Depot said Tuesday that May-July revenue rose 23% year-on-year to $38 billion.Walmart, meanwhile, said comparable US sales excluding fuel rose 9% year-on-year.Not surprisingly, the DIY business is doing well, but valuations also speak to the future.Although Walmart excels at ecommerce, it competes more directly with Amazon than Home Depot.Arguably, this has the advantage of being a business that needs physical showrooms and handles items large enough to be difficult to sell online.The company's sales per retail square foot rose 24% in the quarter.It has also made online shopping more fluid.The direct relationship with the construction contractors is an additional advantage.There's another reason for its valuation success: rock-bottom interest rates, which have helped US home sales rebound. Home Depot's facelift is more than just a paint job.The authors are columnists for Reuters Breakingviews.The opinions are yours.The translation, by Carlos Gómez Abajo, is the responsibility of CincoDías