Do home-improvement retail stocks make a good home for investors' hard-earned cash? Home Depot's(NYSE: HD) and Lowe's (NYSE: LOW) most recent quarterly results should prompt caution, not bullishness, among investors.

Lowe's second-quarter net income increased 9.6%, to $832 million, or $0.58 per share. Total sales rose 3.7%, to $14.4 billion, while same-store sales climbed 1.6%.

Despite those positive signs, Lowe's foundation showed more than a few cracks. Analysts had expected earnings of $1.42 this time around. The company also lowered its top- and bottom-line guidance. It now expects earnings of $1.38 to $1.45 per share for the year, as opposed to its previous guidance of $1.37 to $1.47. Lowe's also believes revenue for the year will be weaker than expected, at $49.1 billion versus analysts' expectation for $49.6 billion.

Home Depot seemed to be on a parallel track. Second-quarter net income increased 6.8%, to $1.2 billion, or $0.72 per share. Total sales crept up 1.8%, and same-store sales increased 1.7%.

The home-improvement behemoth actually beat analysts' expectations for $0.71 per share in earnings, but it missed the $19.59 billion in revenue that Wall Street expected. Home Depot raised its earnings outlook for the year, but don't break out the champagne yet; the increase owes mostly to stock buybacks, and Home Depot's revenue growth isn't looking so great for the rest of the year.

It's no secret that consumers are still strapped, and that the economy remains in dire straits. General merchandise discounters like Wal-Mart (NYSE: WMT), Costco (Nasdaq: COST), and Target (NYSE: TGT), all of which sell consumer necessities, all sound like better defensive stock ideas than their more discretionary home improvement retail stocks. Home Depot and Lowe's will both need increased consumer confidence in the economy (and the housing market) to drum up any really impressive growth in their top lines.

The second half of this year could make home-improvement stocks real homewreckers for investors' portfolios. If these investments come calling, Fools, tell them you're not at home.

Home Depot, Lowe's, Costco, and Wal-Mart are Motley Fool Inside Value picks. Costco is a Motley Fool Stock Advisor recommendation. The Fool owns shares of Costco and Lowe's. Try any of our Foolish newsletter services free for 30 days.

Alyce Lomax does not own shares of any of the companies mentioned. The Fool has a disclosure policy.