Mobile Home Vapor Barrier & Underbelly Repair in Edinburg, TX

The underbelly of a manufactured home is the sealed sheet under the floor that holds the insulation up and keeps ground moisture, dust, and animals out of the floor cavity. When it tears, the floor above it gets wet, the insulation sags, and the ductwork and plumbing that run in the belly are exposed. We arrange repair and replacement across Edinburg and Hidalgo County through licensed, insured Texas installers, along with the ground vapor retarder that Texas’s installation standard calls for underneath. Patches run $300 to $800. A full replacement runs $1,200 to $2,500 on a singlewide and $2,500 to $4,500 on a doublewide. The crew checks the belly during every free level check.

What is under the floor, and what Texas expects there

Two layers matter, and they are often confused.

The bottom board, or underbelly. A sheet of reinforced fabric or board fastened to the bottom of the floor joists. Above it sits the insulation, then the subfloor, then your flooring. The heating and cooling ducts and the water and drain lines run through this cavity. The bottom board is what keeps it dry and closed.

The ground vapor retarder. Plastic laid on the dirt itself. Texas’s generic standard at 10 TAC 80.22(b) specifies “minimum 6 mil polyethylene sheeting or its equivalent, installed so that the area under the home is covered with sheeting and overlapped approximately 12 inches at all joints,” with any tear over 18 inches taped and the laps weighted down. Small tears around footings and anchor heads are allowed.

The same rule sets the ventilation that keeps the crawl space from becoming a swamp: 1 square foot of net free vent area for every 150 square feet of floor, at least six openings, one at each end and two on each side, with a vent within 3 feet of every corner. The rule works the example itself: a 16 by 76 single section has 1,216 square feet of floor and needs 8.1 square feet of open vent. Under 10 TAC 80.21(f), whoever installs the skirting is responsible for the vapor control and the cross ventilation, which is why skirting and belly work belong to the same visit.

Most homes in the Valley have some version of the bottom board and no ground sheet at all. That was fine on dry loam in a dry year. It is not fine on clay after a wet one.

Why bellies fail here

Settling. A home dropping onto piers drags the belly across cap edges and anchor heads. On the Harlingen and Mercedes clays that swell and shrink south of Pharr and east of Weslaco, the frame moves every season, and every move is a new tear. Level the home before you fix the belly or you will fix it twice.

Water. Hidalgo County has had three floods in a decade that put water under and into homes. The June 2018 event dropped 18.31 inches on a gauge west of Mission and 15.57 inches on Weslaco, with the Weather Service estimating at least 2,700 residences and businesses flooded in Mission and McAllen. Hanna in July 2020 left 18 inches to 4 feet of standing water east of Edinburg and in the Mission and La Joya area. A belly that sat in that water filled like a bathtub. Insulation that got wet in 2018 and was never pulled is a subfloor problem now.

Heat. August normals a 99.6 degree high at McAllen, and the ground under a skirted home with too few vents holds humidity against the bottom board all summer. Condensation from cooling ducts running through a hot belly adds to it. Plastic and fabric bottom boards go brittle in that heat and split along the fasteners.

Animals. A skirting gap is an invitation, and once something is living in the belly the insulation comes down in armfuls.

Plumbing work. Every plumber who cut the belly to reach a drain line and stapled it shut with a scrap of tape left a hole that opened the next summer.

What the crew does

Inspect. Under the home with a light, the whole length. Tears, sags where the insulation has dropped, staining that says water got in, damp or matted insulation, exposed ducts, and animal sign. Above, the crew checks the subfloor at the wet spots, because a soft floor over a sagging belly is usually the same water.

Patch. Small tears and plumbing cutouts get sealed with belly repair fabric and the tape made for it, not duct tape. Sagging sections get re-supported. Wet insulation in a patch area gets pulled and replaced.

Replace. When the bottom board is torn in more places than it is whole, or the insulation is soaked across a large area, the old belly comes down, the wet insulation comes out, the floor cavity dries, new insulation goes up, and a new bottom board is fastened and sealed along the frame. Ducts get inspected and re-sealed while they are exposed. Doublewides take longer because the marriage line has to be closed properly.

Ground sheet and vents. Six-mil polyethylene laid and overlapped to the rule, skirting vents counted against the 1-per-150 rule and added where short. See skirting repair.

Check the drainage. A belly replaced over ground that still floods will fail again. The crew looks at where water comes from and says so.

What it costs

Full replacement costs more when the insulation is soaked and has to come out, which is the common case on the clay flats and in any home that stood in floodwater. It costs less on a singlewide on dry Hidalgo loam that just has a brittle, sun-split belly. All of it is on the pricing page.

When to call

Call when you can see insulation hanging below the skirting line, when a room smells musty after rain, when the floor near a bathroom or the water heater feels spongy, when the air conditioner runs constantly because the ducts are open to the crawl space, or when anything has moved in underneath. Call before you replace flooring over a wet subfloor. And if your home stood in water in 2018, 2019, or 2020 and nobody has been under it since, get it looked at. See water under the home for what standing water does to the piers as well.

We cover Edinburg, McAllen, Mission, Pharr, San Juan, Alamo, Donna, and Weslaco.