Attached Modular Additions

The Two Uses of Attached Modular Additions

Attached modular additions are sometimes built to create a separate, additional living unit and sometimes to create more living space. Most zoning boards consider any addition with a separate kitchen to constitute a separate living unit, which requires that the wall between the two units must serve as a “fire stop.” The easiest way to accomplish this is to have the modular manufacturer build a fire-rated wall on that side of the addition.

Zoning and Attached Modular Additions

To qualify as an addition, your community’s zoning regulations will require that it be connected to your home. Detached additions are almost always disallowed. You can connect the two by attaching the addition directly to your home or by joining the addition and your home to another room in between, such as a small site-built mudroom or large, modular great room.

Locating Attached Modular Additions

Your property’s topography may limit where you can build an attached addition. If one side of your lot is wetlands or contains a septic system or municipal sewer pipe, you might not be able to build on that side. You will have the same problem, although to a lesser extent, if one side of your land has a steep slope or an outcropping of rock. Although you will want to locate the addition so that the floor plans of your home and addition work well together, you may want to consider an alternative if the preferred location would incur substantial additional expenses.

The modular manufacturer will want to take into account whether the proposed addition will impose structural loads on the existing house or whether the existing house will impose structural loads on the proposed addition.
The modular manufacturer will want to take into account whether the proposed attached modular addition will impose structural loads on the existing house or whether the existing house will impose structural loads on the proposed addition.

Roof Design of Attached Modular Additions

In designing a modular addition, the dealer and GC should make sure that the intersecting roofs shed water and snow properly. This is particularly important when the addition is being built in areas with the potential for heavy winter snow, because the roof of the addition needs to be attached to the existing home so that the two can carry the load together. Depending on how and where the modular addition will be attached, the manufacturer may ask you to hire a structural engineer to determine what needs to be done to make the two structures work together. The engineer may require the GC to beef up the existing roof to carry the additional load.

The windows on the left side of the living room and family room in the existing home will have to be removed, and a new opening will need to be added in the living room to receive the door to the addition’s kitchen. The two left side windows on the second floor on the existing home will also need to be moved if the roof pitch on the addition is steep.
The windows on the left side of the living room and family room in the existing home will have to be removed, and a new opening will need to be added in the living room to receive the door to the attached modular addition’s kitchen. The two left side windows on the second floor on the existing home will also need to be moved if the roof pitch on the addition is steep.

Matching Openings Between an Existing Home and Attached Modular Additions

Before your modular addition is built, the GC must measure exactly where the openings into your existing home are located. The modular dealer will then use that information to line up the connecting openings in your addition.

Scope of Work for Attached Modular Additions

If you are attaching a modular addition directly to the existing home, the GC will need to remove the siding on the existing home’s wall. Any windows or doors on that wall will also need to be removed, and the resulting holes will need to be closed off and finished so they match the home. No matter how well the addition is set alongside the existing home, there are bound to be small gaps between the two. The GC will need to tie the two buildings together on the inside and outside to hide any gaps. Next week I’ll discuss the second-story modular additions.

For more information about building modular additions, see Building a Modular Addition in my book The Modular Home.

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