Mobile home set on concrete pad (C) Daniel FriedmanHow to Inspect the Structure of Mobile Homes, Double wides, Trailers
Part 1, Wind Ratings, Roof Loading Specifications, Energy Zones, Roof Loading Zones, Foundations

  • MOBILE HOME STRUCTURAL DEFECTS - CONTENTS: Mobile home structural inspection guide: how to find and evaluate structural damage to trailers, mobile homes, and double-wides. Also applies to some campers and pick up truck slide-ons. Common mobile home structural defects: rot, insect damage, wind damage, tie-downs, foundations. Mobile & manufactured home foundation pier heights.
  • POST a QUESTION or READ FAQs about inspecting the structural components of mobile homes, doublewides, trailers.
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How to Inspect Mobile Homes or Manufactured Housing for Structural Defects:

Detailed procedures, defect lists, references to standards.

We address mobile home, trailer, or double wide foundation problems with supporting piers or continuous foundations, slabs, tie-downs, hurricane or wind damage, roll-over prevention, and rot or similar structural damage to walls, floors, roofs.

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STRUCTURAL DEFECTS - Inspecting for Mobile Home Structural Defects

Damaged mobile home wall (C) Daniel FriedmanVer.3.5 - 04/25/07, updated through 2014 - Steve Vermilye, New Paltz NY and Daniel Friedman, Poughkeepsie NY, Hudson Valley ASHI Chapter Seminar, Newburgh NY, January 4, 2000, NY Metro ASHI Fall 99 Seminar, Holiday Inn Crowne Plaza, White Plains NY, October 2, 1999.

Readers should also see MOBILE HOME STRUCTURAL & SAFETY DEFECTS for high priority mobile home and double wide structural concerns.

Article series contents

Question: roof is crooked and doors won't shut in cold weather

(Feb 13, 2014) Re-Posted with space after periods in the text: (3 hours ago) Joseph Matteini said:

It has been very cold 0 degrees plus or minus for a month. My enclosed front porch has sliding windows. slanting roof. The roof is higher on the left side above the doorway,making the door not shut evenly. The difference is one inch. This is also starting on the inside door to the home. This has never happened before.This is an open porch of redwood and steps before the porch. It is an 1985 mobile home. HELP!


Without seeing the actual home or sharp diagnostic photos I can only guess that you have either

1. a sagging roof in danger of collapse - THIS IS UNSAFE and needs prompt attention; if this is the case you may need someone to rake snow off of the porch roof as well as to inspect for damage to the structure. We don't want the porch roof to fall in on you

2. A second possibility is that the roof structure has not sagged and begun to collapse but instead frost heaves have pushed up one end of the porch foundation. The hazards if this is the case are more subtle: there could be hidden damage to the floor structure - another collapse risk, or there may be just a trip hazard due to a sloped floor.

If the floor to the porch is level and has not changed, but the roof slope has changed then my first guess is more likely correct.

Watch out: doors that don't open or shut can be unsafe - you can be trapped in the event of a fire

Question: mobile home doors stick

(Feb 25, 2014) lisa kirshkaln said:

I too, like Joseph M. seem to be having a problem. I have noticed both my front and back doors are getting harder to close, the deadbolt in not inline anymore. and some of my floors and walls have separated by an inch or more, my ceilings seem to look like they are being jacked up in spots

. I do have an a-frame roof over the top of the mobile home.(metal) no snow build up. and some of my walls look a little slanted. I assume its from the frost heaves but what can be done. it has ruined quit a few walls and ceilings already. and do you know if home owners ins. would cover this type of problem. (my floors make noises now) I live in Maine, and we will still have some frost heaves for quite some time. thank you for any advice you can give.

Reply: frost heave movement in a mobile home, doors hard to open or shut - unsafe conditions!

Lisa it sounds as if your home is suffering from frost heave movement, and I speculate that with the current weather conditions this is not a time when actual repairs are possible. Here are some immediate concerns and suggestions:

1. Fire safety: be sure that you have working smoke alarms and that you can get the exit doors open. The worst would be to become trapped in a home, unable to exit, in the event of a fire.

2. Electrical and gas or oil safety: if building movement has torn or moved wiring or plumbing enough to break connections those systems could be unsafe. If you smell fuel odors and these can be trace to a gas leak it's time to get out and ask for emergency assistance.

If electrical switches or outlets or appliances that used to work start behaving oddly there is an electrical hazard - shut those circuits off and ask for help from a licensed electrician. There could be similar damage to plumbing drains that could be unsanitary, below the home, but those are less immediately life threatening.

3. Structural safety: when walls, ceilings, or floors seem to have moved, if movement has actually broken apart structural connections I'd be worried about a collapse.

I don't know how your home is built so can't have a clear opinion about how much movement would be dangerous, but in concept, if a floor starts feeling bouncy when it wasn't before, and/or if you could stick a finger into a space between floor and wall or ceiling and wall, a more expert assessment is pretty urgent. When the problem is a frost heave movement and there has been some structural movement it may be possible (and not so costly) to provide temporary support or to add connectors for safety.

Finally, yes contact your homeowners' insurance company and ask for an inspection and assistance.

Keep me posted; you can also send photos for further comment = using our CONTACT link at page top or bottom.

Mobile Home Zone Ratings for Wind Damage, Uplift, and Damage - Mobile Home Wind Ratings

Structural rot in mobile home (C) Daniel Friedman

Wind Zones & Manufactured Home Regulations:

Details about wind zones and wind zone ratings as well as structural requirements and tie-down requirements for manufactured homes are found

Excerpts are below

Leaks at the windows of this mobile home led to water entry in its wall below the window.

The photograph (courtesy of Jeremias, some of our readers on mobile home restoration and renovation) shows severe structural rot to the floor frame structure below the leaky window.

Only a "do it yourself" repair was economically feasible in this case.

Structural rot in mobile home (C) Daniel Friedman

If you were not sure of the difference between modular construction and a mobile home, notice the presence of a steel frame chassis and even wheels or wheel mounting frames located beneath your mobile home, doublewide, or static caravan.

Also notice that oil line on the crawl space floor. Is it leaking or vulnerable to damage or cold temperatures?

Also see the following critical details for protecting manufactured homes and mobile homes or doublewides from wind damage

(3) Snow and roof loads, HUD Design Load Deflection Specifications for Mobile Homes, Manufactured Homes, Doublewides, Singlewides

Manufactured Home Construction and Safety Standards, Part 3280 contains 10 subparts pertaining to General (data plate and certification contents and locations), Plans (dimensions, exits, etc), Fire Safety, Body and Frame, Testing, Thermal Protection, Heating/Cooling and venting systems, Electrical, and Transportation (axles, springs, drawbar). Excerpts below describe roof design & loading specifications & requirements for manufactured homes.

[Click to enlarge any image]

HUD Roof Design Loading Zone Data MAP

(i) Flat, curved and pitched roofs shall be designed to resist the following live loads, applied downward on the horizontal projection as appropriate for the design zone marked on the manufactured home:

Wind Zone (see Map in § 3280.305(c)(4) )

Assumed Snow & Roof Live Loads
Pounds per Square Foot
for Manufactured Homes (HUD)

North Zone 40 psf
Middle Zone 30 psf
South Zone 20 psf
Retrieved 9 April 2015, original source: [note this is a very large PDF that contains other sections. Our live link above has excerpted the Manufactured Home standards section from the HUD document Ed.]

(3) [continued]

(ii) For exposures in areas (mountainous or other) where snow or wind records or experience indicate significant differences from the loads stated above, the Department may establish more stringent requirements for homes known to be destined for such areas.

For snow loads, such requirements are to be based on a roof snow load of 0.6 of the ground snow load for areas exposed to wind and a roof snow load of 0.8 of the ground snow load for sheltered areas.

(iii) Eaves and cornices shall be designed for a net uplift pressure of 2.5 times the design uplift wind pressure cited in §3280.305(c)(1)(i) for Wind Zone I, and for the design pressures cited in §3280.305(c)(1)(ii) for Wind Zones II and III.

(4) Data plate requirements [for wind & roof load zones]

The Data Plate posted in the manufactured home (see §3280.5) shall designate the wind and roof load zones or, if designed for higher loads, the actual design external snow and wind loads for which the home has been designed.

The Data Plate shall include reproductions of the Load Zone Maps shown in this paragraph (c)(4), with any related information. The Load Zone Maps shall be not less than either 31⁄2 in. by 21⁄4 in., or one-half the size illustrated in the Code of Federal Regulations.

(d) Design load deflection specifications: HUD

(1) When a not exceed the following (where L structural assembly is subjected to equals the clear span between supports total design live loads, the deflection or two times the length of a cantifor structural framing members shall lever):

Roof and ceiling—L/180
Headers, beams, and girders (vertical load)—L/180
Walls and partitions—L/180

(2) The allowable eave or cornice deflection for uplift is to be measured at the design uplift load of 9 psf for Wind Zone I, and at the design uplift pressure cited in paragraph (c)(1)(ii) of this section for Wind Zones II and III. The allowable deflection shall be (2 x Lc)/ 180, where Lc is the measured horizontal eave projection from the wall.

(e) Fastening of structural systems. HUD Design Specifications

(1) Roof framing shall be securely fastened to wall framing, walls to floor structure, and floor structure to chassis to secure and maintain continuity between the floor and chassis, so as to resist wind overturning, uplift, and sliding as specified in this part.

(2) For Wind Zones II and III, roof trusses shall be secured to exterior wall framing members (studs), and exterior wall framing members (studs) shall be secured to floor framing members, with 26 gage minimum steel strapping or brackets or by a combination of 26 gage minimum steel strapping or brackets and structural rated wall sheathing that overlaps the roof and floor. Steel strapping or brackets shall be installed at a maximum spacing of 24′′ on center in Wind Zone II and at a maximum of 16′′ on center in Wind Zone III. The number and type of fasteners used to secure the steel straps or brackets or structural sheathing shall be capable of transferring all uplift forces between elements being joined.

(f) Walls, HUD Design Load Deflection Specifications

The walls shall be of sufficient strength to withstand the load requirements as defined in §3280.305(c) of this part, without exceeding the deflections as specified in §3280.305(d). The connections between the bearing walls, floor, and roof framework members shall be fabricated in such a manner as to provide support for the material used to enclose the manufactured home and to provide for transfer of all lateral and vertical loads to the floor and chassis.

(1) Except where substantiated by engineering analysis or tests, studs shall not be notched or drilled in the middle one-third of their length.

(2) Interior walls and partitions shall be constructed with structural capacity adequate for the intended purpose and shall be capable of resisting a horizontal load of not less than five pounds per square foot. An allowable stress increase of 1.33 times the permitted published design values may be used in the design of wood framed interior partitions. Finish of walls and partitions shall be securely fastened to wall framing.

(g) Floors, HUD Design Load Deflection Specifications

(1) Floor assemblies shall be designed in accordance with accepted engineering practice standards to support a minimum uniform live load of 40 lb/ft2 plus the dead load of the materials. In addition (but not simultaneously), floors shall be able to support a 200–pound concentrated load on a one-inch diameter disc at the most critical location with a maximum deflection not to exceed one-eighth inch relative to floor framing.

Perimeter wood joists of more than six inches depth shall be stabilized against overturning from superimposed loads as follows: at ends by solid blocking not less than two-inch thickness by full depth of joist, or by connecting to a continuous header not less than two-inch thickness and not less than the depth of the joist with connecting devices; at eight-feet maximum intermediate spacing by solid blocking or by wood cross-bridging of not less than one inch by three inches, metal cross-bridging of equal strength, or by other approved methods.

(2) Wood, wood fiber or plywood floors or subfloors in kitchens, bathrooms (including toilet compartments), laundry areas, water heater compartments, and any other areas subject to excessive moisture shall be moisture resistant or shall be made moisture resistant by sealing or by an overlay of nonabsorbent material applied with water-resistant adhesive. Use of one of the following methods would meet this requirement:

(i) Sealing the floor with a water-resistant sealer; or

(ii) Installing an overlay of a non-absorbent floor covering material applied with water-resistant adhesive; or

(iii) Direct application of a water-resistant sealer to the exposed wood floor area when covered with a non-absorbent overlay; or

(iv) The use of a non-absorbent floor covering which may be installed without a continuous application of a water-resistant adhesive or sealant when the floor covering meets the following criteria:

(A) The covering is a continuous membrane with any seams or patches seam bonded or welded to preserve the continuity of the floor covering; and

(B) The floor is protected at all penetrations in these areas by sealing with a compatible water-resistant adhesive or sealant to prevent moisture from migrating under the nonabsorbent floor covering; and

(C) The covering is fastened around the perimeter of the subfloor in accordance with the floor covering manufacturer’s instructions; and,

(D) The covering is designed to be installed to prevent moisture penetration without the use of a water-resistant adhesive or sealer except as required in this paragraph (g). The vertical edges of penetrations for plumbing shall be covered with a moisture-resistant adhesive or sealant. The vertical penetrations located under the bottom plates of perimeter walls of rooms, areas, or compartments are not required to be sealed; this does not include walls or partitions within the rooms or areas.

(3) Carpet or carpet pads shall not be installed under concealed spaces subject to excessive moisture, such as plumbing fixture spaces, floor areas under installed laundry equipment. Carpet may be installed in laundry space provided:

(i) The appliances are not provided;

(ii) The conditions of paragraph (g)(2) of this section are followed; and

(iii) Instructions are provided to remove carpet when appliances are installed.

See MOBILE HOME STABILIZING SYSTEMS for details about the tie downs required to protect mobile homes, doublewides, singlewides from earthquake & wind damage.

Mobile Home Energy Zones

(HVAC) New York is in Thermal Zone 3

Mobile Home Roof Zones

(Snow load) NY North of the Thruway = "Middle Zone (30 psf)" and all areas S of the Thruway "Southern Zone (20 psf)"

(Check zone ratings on the home's data plate: wind load, heating load, roof load)

Mobile Home & Manufactured Home Foundation Codes &Defects

Below our photograph illustrates a cable tie-down securing the mobile home's steel frame to a buried anchor (not visible) .

Mobile home founation piers (C) D Friedman S Vermilye

At below right we point out a concrete septic tank that was mistaken for a mobile home foundation slab - do not park a mobile home on top of a septic tank nor over a drainfield or other onsite waste disposal systems.

Mobile home founation piers (C) D Friedman S Vermilye

Some common mobile home, doublewide, or caravan trailer foundation & support defects include:

Question: mobile home maximum pier foundation height

Maxmum pier height 36" for single block stacks (C) from Texas Code

2017/06/07 Ashley said:

What is the maximum height a mobile home can be from the ground?

This question was originally posted at MOBILE HOME CODES & STANDARDS

[Click to enlarge any image]



In general the maximum height from the surface of the pier to the top of the last concrete block which would be placed under a beam or girder supporting the manufactured or mobile home floor is

Please see MOBILE HOME PIERS for complete detail about the construction, codes, and inspection of manufactured or mobile home pier support systems.

Also see MOBILE HOME STABILIZING SYSTEMS since the stabilizing system is a key part of the foundation system you should inspect below your home.

Links to articles found at the "More Reading" links at the bottom of this article or at the end of this article provide details about specific mobile home structural defects and concerns.


Continue reading at MOBILE HOME CONNECTIONS, MULTI-WIDE or select a topic from closely-related articles below, or see our complete INDEX to RELATED ARTICLES below.


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