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Permalink Reply by Moose on June 14, 2012 at 12:08pm

We face Balloon structures a lot in my area, being we are all rural with a lot of old farm houses.  Some of these houses were built prior to codes enforcement just to give you an idea, and then you get current owners buying the house and doing rennovation work, yet they only build OVER existing features, making a void space.

I remember at one fire we went to pull ceilings and found 3 layers of ceiling; sheetrock, then plaster and lathe, than a ceiling higher up with a tin covering with a 3 foot void space.  APparrently it was a make shift drop down ceiling to make it easier to heat in the winter, making 10 foot ceilings into 7 foot.

Fires spread down in these buildings just as fast as spreading up, with embers dropping down the wall spaces and catching insulation or other combustible materials on fire, before you know it you are cut off from the way you came in from advacing fire from the basement or first floor.  Tricky fires to fight if you do not perform a constant size-up throughout the operation.

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Permalink Reply by FETC on June 14, 2012 at 2:29pm

So true Brian, good points to ponder.  They do burn down as fast as up. The difference here is these new dwellings are using lightweight wood and yours are dimensional lumber. So in essence they burn faster and hotter due to the (HRR) Heat Release Rate. Your dimensional lumber has the 1 inch char per hour rating. We are talking about an entire house fully involved in little as 8 minutes.

 

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Permalink Reply by ashfire on June 22, 2012 at 10:54pm

If the government quit taking the money from the building industry to look the other way while they build cheap and charge more for something that ain't worth the ground it sets on. The builders want to stop sprinklers for single or two family homes. I guess next will be cheap wiring in more homes.

I would rather buy  a old house to a new house built today or one built with stone, brick or  concrete.

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Permalink Reply by Jack/dt on June 27, 2012 at 1:20pm

ashfire;

Everything is not a conspiracy.  Using faster, less expensive methods and materials mean faster and less expensive housing.  In the spirit of true *capitalism* the idea here is to make money.

Near as I've ever been able to figure it out, the only reason I come up with for the NAHB to be against residential sprinklers is that there's more money to be made for NAHB members in building a new house than there is in re-building a saved, sprinklered one.

As for old homes, even just back to the 60's, building codes were very lax and many homes were homeowner remodeled, often not even meeting the codes of the time.  In the 60's to 70's aluminum wiring was used as a 'cheaper' alternative to copper.  You don't see that anymore, ever wonder why that is?

Stone, brick and concrete houses can and do burn down.  Maybe not a complete structural loss (especially concrete, unless it's badly spalled from heat) but many a stone cathedral has burnt to the ground.

It boils down to national, state and local building codes (and code enforcement).  Have you ever drilled through a sill plate to run a wire for a new outlet, or for phone or CATV?  Did you then caulk that hole with fire retardant caulking?  Ever re-roof your house?  Did you overlay over more than two layers?  Did you use the proper size nails and correct number of them that your code calls for?  Did you pull a permit if required and get an inspection?

Billy;

I listened to your program (after the fact) and have been looking at the photos, and a couple of questions come to mind:

1) Don't local codes call for closing in the void spaces? (Pretty sure that any modular that comes into my town has to meet local code and I don't think either the BD or the FMO would allow anything that didn't meet code.)

2) What about fire retardant caulking for purchase points as well as wire chases?

3) Why is the rim joist a stacked 2x12 (2x24) with ceiling joists 2x6 24 OC and the floor joists 2x10 16OC?  What was gained by double building the ceiling/floor?

4) Is the foam adhesive used to glue up the drywall anymore flammable than blown in insulation?

5) I thought I had it but can't find a PDF of a study on the heat resistance of the adhesive used in engineered trusses.  The upshot of it was that the adhesive did not fail from exposure to heat/flame (although clearly the lighter weight material and faster burn through times may make that a moot point.)

6) Can't local codes supersede/exceed those of the state or national code book?

I'm not arguing that nothing should be done, on the contrary it strikes me that local codes and enforcement can prevent the kind of fire(s) you discussed.  Engineers will always tinker and do Engineery things, as will architects and so long as what they do can be balanced against the need for safety I see no problem with utilizing new methods and materials.  And should there arise methods or materials that either are suspect or become suspect then they should be curtailed at the local level until the manufacturer or builder can prove otherwise.  But at the very least, the local BD should be aware of the voids and potential hazards and, along with the FD have a pre-plan.

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Permalink Reply by FETC on June 27, 2012 at 3:05pm

Jack thanks for taking the time to listen to the radio show link. It is a real eye opener for many firefighters who think they understand the hazards of lightweight construction, but add in modular and they are even more behind the curve.

 

First off - The modular industry is meeting the requirements of all codes. Even in the pictures and past fires that have occurred, those were code compliant dwellings from the factory. So let me try an answer your questions...

 

1) Don't local codes call for closing in the void spaces? (Pretty sure that any modular that comes into my town has to meet local code and I don't think either the BD or the FMO would allow anything that didn't meet code.)

 

No, they don't require closing the voids in single and two family dwellings. Modular construction in your community looks the same. The local BD and FMO have no say as to make them.  These units are nationally accredited and your state FMO and BD accept them.

 

2) What about fire retardant caulking for purchase points as well as wire chases?

 

Yes purchase points and wire chases are supposed to be protected.  The issue is with a modular, there are far less inspections from BD or FMO as most of the dwelling has been constructed in the factory and buttoned up before being shipped. The next issue is the IRC is looking to add verbage for draft stopping which would require protecting the larger void space with sprinklers or closing off the void and filling that space with batting.

 

3) Why is the rim joist a stacked 2x12 (2x24) with ceiling joists 2x6 24 OC and the floor joists 2x10 16OC?  What was gained by double building the ceiling/floor?

 

What is gained is strength for shipment over the road.  Anything less would twist and therefore each box would be damaged from transit.  The industry makes these on a production line and they are made that way regardless if it is a one story ranch or a two story colonial. Therefore when you stack the boxes for a two story, they create more void space in between the first floor ceiling and the second floor - floor. As far as the spacing on the floor joist (16"o/c) verse ceiling joists (24" o/c) The floor requires that spacing per code for strength, (weight load), the ceiling is only there to hold up the sheetrock. Therefore when you stack them the void is 18 or 20" in height and because the floor and ceiling joists are offset we now have the same height void accross the entire dimensions of the floor plan horizontally. So if the house is 20'x40' times that by 18" or 20" high. In essence a cockloft. 

 

4) Is the foam adhesive used to glue up the drywall anymore flammable than blown in insulation? 

 

I  am not sure what the rating temps are of blown in isulation. The glue here is tested for heat exposure and resistance. But placing a direct flame in contact and the glue used in these will ignite fairly quickly.  The other issue is the glue is an expanding foam type gorilla glue. It starts to change physical properties, solid to a liquid at fairly low temps. Sheetrock has a protection factor of about 42% therefore ceiling temperatures in a room and contents fire of a 1000 F equates to 426F on the backside of that sheetrock, (this is where this glue is attached)  The next issue that firefighters do not understand is there is a rule that says glued and screwed, BUT an administrative rule allows one or the other if it clearly holds the sheetrock in place. Some of these modulars (SOME NOT ALL) are using just GLUE instead of any sheetrock screws.  Now, I have read of firefighters saying they were momentarily trapped from a partial ceiling collapse. Add up the room temps with glue only and sheetrock can start falling off the ceiling and walls fairly early. Trapping firefighters and opening up voids that simply would not exist in stick built.

 

5) I thought I had it but can't find a PDF of a study on the heat resistance of the adhesive used in engineered trusses.  The upshot of it was that the adhesive did not fail from exposure to heat/flame (although clearly the lighter weight material and faster burn through times may make that a moot point.) 

 

Not the same glue. And in the engineered trusses the glue is protected by the wood mass because of the finger joint. The glue here in modulars is not under the sheetrock (between the stud and the back face) it is sprayed onto the side of the stud and onto the back face of the sheetrock to adhere (no protection)

 

6) Can't local codes supersede/exceed those of the state or national code book?

 

All depends if your community has ordinaces in place to superceed the national code. Many do not because they simply do not understand the hazards.  We didn't even scratch the surface of the hazards. Like having an out of square foundation and thus creating new unengineered voids vertically as well.

 

Alot of these voids are commonly seen in multi-family with lightweight engineered beams, but those are required to have protected void spaces because it is a different code for multi family or commercial occuopancies.  Single and two family are currently not.

 

Hope this answers some of your questions, I like to read your comments because they are usually well thought out, researched and educated.  My reason to bring this to light was to educate firefighters in the dangers they may not understand about a single or two family dwelling.

 

 

 

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Permalink Reply by Jack/dt on June 27, 2012 at 3:48pm

Billy,

Thanks for taking the time to sort it out for me.  I have a pretty good understanding of legacy and lightweight construction and around here all of the new houses are comprised of a combination of the two. 

As for modular, I only know of two (that I have been in) that were *built* in the early 90's.  I don't think that modulars are that common in my town, although pretty much everything being built is, as I pointed out above, a combination.

So then really if a town chooses to they can have local building codes that exceed the national code?  If this is the case it seems the simplest case is for the local AHJ to enact ordinances that require the 'cockloft' and other voids to be fire blocked or otherwise close in.  If enough towns (or states, for that matter) required these voids to be closed off eventually the manufacturers would incorporate those local codes into their own methodologies, thus eliminating the issues you discussed on your program.

I know somewhere in your program you (or your guest) mentioned having the code changed to require blocking (or closing off of void spaces) that were larger than about 600 ft. sq?  Seems like a good start but, a void that is less than 600 ft.sq. is still a huge space.

Your program was indeed an eye opener (at least for me), keep up the good work.

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Permalink Reply by FETC on June 27, 2012 at 10:11pm

Well even during the fight, find a marriage wall and see if you can wrap you hands around the trim. Modulars have 2x6 walls in both the first floor boxes, therefore the opening in the marriage wall should be about 12" trimmed out compared to a stick built frame that will be 2x4 or 2x6 dependant on a weight bearing wall or not.  I am going to take some pics. In every fire I find the marriage wall to identify the construction during the fight.

 

Stay safe

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Permalink Reply by Jack/dt on June 28, 2012 at 9:06am

In the pics from your program, you show a view looking up, between the marriage wall.  Does this mean that there is (always) a gap, or void between the two walls?  If so then there is a void from basement to second floor/attic?

Also, are the studs in the marriage wall aligned with each other, or offset a bit, allowing a horizontal void as well?

Key point you made though is the width of the marriage wall, I hadn't considered that.  Yes, typical width of the central bearing wall (or any wall, for that matter) is around 4 1/2" (2x4) and 6 1/2" (2x6) so anything greater than that clearly implies a marriage wall between two modular boxes.  Great thing to keep in mind and, I suspect, one of the only ways to quickly identify a modular home (even in the dark).

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Permalink Reply by FETC on June 28, 2012 at 12:07pm

Most building construction classes do not even address modulars as a concern.  The width of the marriage wall would be a nugget from my construction class. I can clearly identify modular construction from the center marriage wall even in low visibilty IDLH. The next place is to go look underneath the sink and you will find a large decal with the national certification for code compliance.

 

Are the voids all like that?  No if the foundation is square and poured within specs then there will be no vertical voids.  Now if the foundation is out of square, what happens is they will flush the front box to the front edge of the foundation and the rear exterior wall of the back box to the rear of the foundation's sill and thus creating the center marriage wall void. If they flush the marriage walls they will have an ugly foundation shelf sticking out beyond the house. The void is really noticed when you walk around the exterior post set, and look at the gable end that is out of square. I have seen some crews just quickly wrap the exterior with tyvek moisture barrier and then start putting up the vinyl siding. Remember the BD or FMO is usually not on scene during the set. My recommendations is on the day of the set, that they make a friendly spot inspection, or when the foundation is poured, that they actually use a tape measure to cross measure the foundation work.  Most stick builders will eat up an out of square foundation as they frame (hence out of square interior walls later when you want to renovate)  Outside fires on that end is going to have some significant access to not only that end but throughout the entire dwelling just like a balloon frame

 

 

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