New Building Construction and Resident Rats

By Chris Williams on April 24, 2014.

Brown rats at new building


I manage an apartment property in a Boston suburb. We recently added a brand new building to the complex and we just discovered that the building has rats inside! We think there are at least six rats. We’ve never had rats in any of the other buildings and haven’t even seen any on the property in years. How do we manage to kill rats running loose in a large building? C. P., Arlington, MA


First, don’t try to do it on your own. Contact an exterminating company. Norway or brown rats can become a new issue during building construction, or even renovation, when their home turf is disturbed. There are preventive steps that could have been taken before construction to help prevent this scenario, but now you need the services of a professional who can design a rat management program for your property. Don’t delay.

You may not have had rats living on your property before, but if the new building borders on other properties that have rats, they could have been enticed by the nearby construction. Construction materials stacked and stored on site provide lots of desirable hiding places for rats. Construction workers leave food scraps around the site. If you’re a rat, the loose dirt around a construction site is good for burrowing. During construction, walls and windows are left open for months, letting rats move inside. Your rats may have entered during construction and are now trapped in the building, or they may be moving in and out through unseen openings. A pest control inspection can determine which is the case.

Trapped Rats Can Move Throughout the Building Inside the Walls

In the late construction phases, interior partition walls and doors are added, utility lines completed, and the building sealed off into distinct areas. If the building was well rodent-proofed after construction, rats may have been sealed into the wall voids. Once inside the walls though, rats can move from apartment to apartment or floor to floor without even leaving the void space.

If the building is not yet occupied and won’t be for some time, you have more leeway in control options. If the building is occupied, it’s always best to use rodent traps so that you can remove the carcasses. If there are already tenants in the building, the stench of inaccessible dead rats in wall voids will not be appreciated.

In advance of the exterminator’s inspection, you can make note on a property map of where you are seeing rats or evidence of rats such as  droppings. If the building is still empty, you’ll want to keep it that way while you work on rat elimination. Make sure that there is no food garbage of any kind in the building, and reexamine your trash handling on the grounds. Check for any rat burrows on the property grounds.



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