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

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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.

This article series 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.

We also provide a MASTER INDEX to this topic, or you can try the page top or bottom SEARCH BOX as a quick way to find information you need.

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, required labeling and specifications for manufactured homes and mobile homes built after 1976, 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 [PDF] 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

Notes to the table above

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 Manufactured Homes & Mobile Homes [including wind & roof load zones]

The Data Plate posted in the manufactured home (see §3280.5) [for homes built after 1976] 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.

Excerpts from U.S. HUD CFR › Title 24 › Subtitle B › Chapter XX › Part 3280 › Subpart A › Section 3280

§ 3280.1 Scope.

This standard covers all equipment and installations in the design, construction, transportation, fire safety, plumbing, heat-producing and electrical systems of manufactured homes which are designed to be used as dwelling units.

This standard seeks to the maximum extent possible to establish performance requirements. In certain instances, however, the use of specific requirements is necessary.

§ 3280.5 Data plate.

Each manufactured home shall bear a data plate affixed in a permanent manner near the main electrical panel or other readily accessible and visible location.

Each data plate shall be made of material what will receive typed information as well as preprinted information, and which can be cleaned of ordinary smudges or household dirt without removing information contained on the data plate; or the data plate shall be covered in a permanent manner with materials that will make it possible to clean the data plate of ordinary dirt and smudges without obscuring the information.

Each data plate shall contain not less than the following information:

(a) The name and address of the manufacturing plant in which the manufactured home was manufactured.

(b) The serial number and model designation of the unit, and the date the unit was manufactured.

(c) The applicable statement:

This manufactured home is designed to comply with the Federal Manufactured Home Construction and Safety Standards in force at the time of manufacture.or

This manufactured home has been substantially completed in accordance with an approved design and has been inspected (except for the components specifically identified in the instructions for completion on-site) in accordance with the Federal Manufactured Home Construction and Safety Standards and the requirements of the Department of Housing and Urban Development (HUD) in effect on the date of manufacture.

(d) A list of the certification label(s) number(s) that are affixed to each transportable manufactured section under § 3280.8.

(e) A list of major factory-installed equipment, including the manufacturer's name and the model designation of each appliance.

(f) Reference to the roof load zone and wind load zone for which the home is designed and duplicates of the maps as set forth in § 3280.305(c). This information may be combined with the heating/cooling certificate and insulation zone map required by §§ 3280.510 and 3280.511. The Wind Zone Map on the Data Plate shall also contain the statement:

This home has not been designed for the higher wind pressures and anchoring provisions required for ocean/coastal areas and should not be located within 1500′ of the coastline in Wind Zones II and III, unless the home and its anchoring and foundation system have been designed for the increased requirements specified for Exposure D in ANSI/ASCE 7-88.

(g) The statement:

This home has - has not - (appropriate blank to be checked by manufacturer) been equipped with storm shutters or other protective coverings for windows and exterior door openings.

For homes designed to be located in Wind Zones II and III, which have not been provided with shutters or equivalent covering devices, it is strongly recommended that the home be made ready to be equipped with these devices in accordance with the method recommended in the manufacturers printed instructions.

(h) The statement: “Design Approval by”, followed by the name of the agency that approved the design.

[ 59 FR 2469, Jan. 14, 1994, as amended at 80 FR 53727, Sept. 8, 2015]

§ 3280.6 Serial number.

(a) A manufactured home serial number which will identify the manufacturer and the state in which the manufactured home is manufactured, must be stamped into the foremost cross member. Letters and numbers must be 3/8 inch minimum in height. Numbers must not be stamped into hitch assembly or drawbar.

§ 3280.11 Certification label.

(a) A permanent label shall be affixed to each transportable section of each manufactured home for sale or lease in the United States. This label shall be separate and distinct from the data plate which the manufacturer is required to provide under § 3280.5 of the standards.

(b) The label shall be approximately 2 in. by 4 in. in size and shall be permanently attached to the manufactured home by means of 4 blind rivets, drive screws, or other means that render it difficult to remove without defacing it. It shall be etched on 0.32 in. thick aluminum plate.

The label number shall be etched or stamped with a 3 letter designation which identifies the production inspection primary inspection agency and which the Secretary shall assign.

Each label shall be marked with a 6 digit number which the label supplier shall furnish. The labels shall be stamped with numbers sequentially.

(c) The label shall read as follows:

As evidenced by this label No. ABC 000001, the manufacturer certifies to the best of the manufacturer's knowledge and belief that this manufactured home has been inspected in accordance with the requirements of the Department of Housing and Urban Development and is constructed in conformance with the Federal manufactured home construction and safety standards in effect on the date of manufacture.

See date plate.

(d) The label shall be located at the tail-light end of each transportable section of the manufactured home approximately one foot up from the floor and one foot in from the road side, or as near that location on a permanent part of the exterior of the manufactured home unit as practicable.

The road side is the right side of the manufactured home when one views the manufactured home from the tow bar end of the manufactured home.

[ 42 FR 960, Jan. 4, 1977. Redesignated at 44 FR 20679, Apr. 6, 1979, as amended at 52 FR 47553, Dec. 15, 1987. Redesignated and amended at 58 FR 55003, Oct. 25, 1993]

(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 ARTICLE INDEX the bottom of this article or at the end of this article provide details about specific mobile home structural defects and concerns.

Manufactured & Mobile Home Body & Frame Construction Requirements & Standards

Full text of the manufactured and mobile home heating standards can be found in

PART 3280—MANUFACTURED HOME CONSTRUCTION AND SAFETY STANDARDS [PDF] newer copy retrieved 2017/07/13 - faster-loading

See Subpart D, Body and Frame Construction Requirements in that document.

That subpart includes these sections

Ver5 - 2018 01 13 updated through January 2018 - 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.


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.

Or see MOBILE HOME STRUCTURAL DEFECT FAQs - questions and answers about mobile or manufactured home structural problems posted originally at this page.


Or see this

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