LAKEWOOD, Colo (CBS4) – More home builders are halting construction on new homes across the Front Range because of joists coated with formaldehyde. The boards are meant for fire resistance, but the problem has forced many people out of their homes and kept hundreds of others from being able to move in.

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At a new development being built by Cal Atlantic in Lakewood, work has stopped on some homes, and warnings spray painted on garage doors that say, “Don’t Walk Inside”. Residents who’ve already moved into their new homes are now wondering.

“After hearing about the problem with the formaldehyde, it’s like, ‘Do we have it and we haven’t been told,’” said Karen Keuter, a new homeowner.

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The problem involves floor joists made by Weyerhaeuser. Specifically those manufactured since December of last year. The formula of the coating for fire resistance was changed and involves formaldehyde. Environmental physician, Karin Pacheco, at National Jewish Health said the danger is most likely limited.

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“The principle effects of formaldehyde are mostly irritation: eye burning, nose burning, throat burning, mouth burning, headaches. And those are at pretty low levels,” Pacheco told CBS4’s Rick Sallinger.

She said those who work with formaldehyde all their lives are more likely to come down with effects like cancer.

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“You weren’t told about any problems?” Sallinger asked another neighbor who shook his head no.

Still those who live in the Green Gables neighborhood, including those not affected, are concerned about their homes, their health and their property values.

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Weyerhaeuser is offering to either replace them in the homes, or cover them with a protective coating.