Sdrhcon2011 morris

www.fpinnovations.ca

Design and Treatment Specifications for Durable Disaster Relief Housing

Paul Morris and Jieying Wang

Durability and Protection Group FPInnovations

Durability Concerns for Disaster Relief Housing

• Need to maximize number of shelters pushes down cost which leads to simplified designs with fewer moisture management features

• May be difficult to control construction quality• Temporary structures tend to become permanent• Occupier improvements may increase moisture

and termite problems– Addition of untreated wood invites decay and termites– Addition of concrete embeds wood– Addition of cladding or insulation hides termites

Durability Concerns for Disaster Relief Housing

In tropical/subtropical countries• High humidity and rainfall promotes decay• Warm temperatures favour termites

In extreme northern climates• High occupancy - high interior moisture load• High insulation can promote condensation

Understanding the Decay and Termite Hazard

• Scheffer index values indicate decay potential– Derived from equation using rainfall and temperature data

• 3 main divisions in termite hazard zones1. No termites – wood boring beetles may be a problem2. Reticulitermes and other termite species. No Coptotermes3. Coptotermes species present, drywood termites also likely

• Get expert advice

Beetle attack on local hardwood in Aceh

Native termites in Haiti

• Subterranean termites Reticulitermes sp.• Drywood termites Cryptotermes sp.• Tree-dwelling termites Nastitutermes sp.

Coptotermes formosanus is the world’s most economically important termite pest

Potential Transport of Coptotermes to Haiti etc.

Drywood termites

Formosan termites ?

• Termites can be transported via trade or aid.

Native termites in Indonesia

• Copotermes gestroi mainly in cities– C. formosanus sophisticated cousin

• Coptotermes curvignathus mainly in rural areas– C. formosanus hillbilly cousin

• Best to consider all Coptotermes as equally bad• ~198 other species

• Deflection– Divert water

• Drainage– Let water go

• Drying– Allow to dry

• Durability– Durable materials

Hazleden, D.G., Morris, P.I. 1999.

Moisture Management

Moisture ManagementThe 4Ds

Design Solutions for Durability

Moisture Management

Moisture ManagementVapour Control inNorthern Climates


Vapour/air barrier on the inside

Moisture Management

Moisture ManagementVapour Control inTropical Climates


Vapour/air barrier on the outside


• Pitched roof with overhangs on all sides• Minimize penetrations in roof• Minimize rainfall traps• Minimize wood-soil contact

– Even if treated, this can attract termites• Minimize penetrations through slab

– Termites enter through cracks• Design should be congruent with local custom


• Support posts above concrete– Prevent wicking of water– Facilitate inspection for termites

• Raised floor– Reduced flood damage– Improved ventilation– Facilitates inspection and termite control

Ain’t nobody here but us chickens

Chickens eating tree-dwelling termites in Cuba

Integrated Termites Management : The 6Ss

BUG OFF

Soil barrierSlab/foundation

Structural

durabilitySite management

Surveillance

Suppression

Slab/foundation

Developed Countries


Slab/foundation

Structural

durabilitySite

management

Slab/foundation

Disaster Relief

Slab/foundation


Slab/foundation

Structural

durabilitySite management

Slab/foundation

Subterranean termites

Drywood termites

Tree dwelling termites

Formosan termites?

Slab/Foundation detailing does not stop all termites

Integrated Termite Management

Structure Durability• Most of our species are not termite resistant• Exceptions:

– Western red-cedar is non-preferred but still gets eaten– Eastern white-cedar is non-preferred but still gets eaten– Yellow cedar is the most termite resistant

• For most species, treatment is the only option– Note: thermal treatment is not effective vs termites

Preservative Treatment Options

Not only the lumber needs to be treated• Plywood and PSL can be pressure treated• OSB can be treated during manufacture• LVL very difficult to treat – avoid• I-joists need to be made from treated material• Glulam reacts badly to waterborne treatment

– Oil borne preservatives not appropriate for residential – LOSP (Hi-Clear or Cu-nap) treatment not available in Canada– Can treat lamina prior to gluing


Must consider• Regulations in exporting country• Regulations in importing country• Potential for human contact• Building design• Wood species• Local decay and termite hazards


• Many countries have their own standards– Former British colonies may use British (European) standards– American dependencies use AWPA standards– French colonies may use French ( European) standards

• All should be using ISO 21887 Use Classes– UC 1 Interior, dry– UC2 Interior, damp– UC3 Outdoors above ground– UC4 Outdoors ground contact


• Canadian species mostly impermeable heartwood• Tough to meet foreign treatment standards• After intensive research by FPInnovations and

UBC, Canadian standards for outdoor residential lumber have been reduced– No penetration requirement for 2x4 and smaller

• These specifications are fine for northern climates• Not for tropical/subtropical regions• Shallow penetration won’t stop termites


• ACQ and CA Pressure Treatment– Require incising (perforation) - 25% strength loss– React with wood. Stop moving when pressure stops

• Borate Pressure+Diffusion Treatment– Does not require incising– Don’t react with wood. Keep moving when pressure stops

• New surface-applied penetrating process– Chemistry and process provide deep penetration

• In process Zinc-borate treatment of OSB• Surface-treatments


• ACQ – Copper ethanolamine – algaecide for pools and hot tubs– Quaternary ammonium – disinfectant for surfaces and swabs

• CA– Copper ethanolamine – algaecide for pools and hot tubs– Azole – related compounds in dandruff shampoo/athletes foot cream

ACQ and CA pressure treatment• Choice of species is critical


High-density Incised White SpruceIncised white spruce Incised Pacific Silver fir


Termites eat through a thin shell of treatment


Termites give up if treated shell is thick enough


Or, if they get through, the box is strong enough


• That is why I favour borate treatment• Borates penetrate our wood

Red colour with reagent shows borate penetration

• Got it on your hands?

• Got it on your clothes?.

• Got it in your eyes?

• Got hungry?


• Got boron ?

Borates have a positive perception

600mm

400mmm

1000mm


Above ground protected termite test


0

1

2

3

4

5

6

7

8

9

10

0 2 4 6 8 10Years of exposure

AW

PA

term

ite ra

ting

hem-fir control ACZA 2% shell 3% shell2% through 3% through 2%+DDAC CCA

Performance of treated samples in Hawaii


• In Hawaii almost all wood-frame homes are 100% borate treated.

• Higher loadings required for Formosan termites than in CSA – Use AWPA standards

• Borates not for use outdoors exposed to rain– Except under well maintained 3-coat paint finish


New surface-applied penetrating process• Developed for New Zealand market• Penetrating formulation

– Various fungicides and insecticides can be added• Dip or spray

plus kiln-conditioning

New surface-applied penetrating process


Treatment results on BC SPF (pine)

Red colour with reagent shows penetration


Treatment Rating (10-0) at 2 yrs

Control (untreated) 2

Borate (sub-standard) 8

Formulation 1 9

Formulation 2 10

Formulation 3 10

New surface-applied penetrating process


• ZB added to OSB during manufacture• Added as a powder at the blender• Effectively treats full cross section• ZB is resistant to leaching• Factory coated/sealed boards for

exterior use• Field tested in Hawaii*

*Image courtesy of Peter Laks, Michigan Tech University


• OSB Treated with ZB During Manufacture

Data courtesy of Peter Laks, Michigan Tech University


Other Treatments• What are the active ingredients?

– Vs decay– Vs termites

• What loading is achieved?• What penetration is achieved?• What standards are met?• What long term field test data are available?

– Lab testing is not good enough – small samples easily treated• What are the warranties?

Preservative Treatment Specifications

• Treated wood off the shelf likely won’t perform• Don’t accept “treatment to refusal”• Get expert advice• Specify standard and subsection• Specify preservative and species• Treatment certificates are worth

the value of the paper and the ink• Use third party quality assurance


• For Britco pre-fab homes for tsunami reliefin Indonesia we recommended to FII:– ACQ treated plywood sheathing – no cladding supplied– Incised ACQ treated hem-fir for outside– Borate treated SPF for inside

protected from rain


• For home kits for earthquake reliefin Haiti we recommended to SNC Lavelin:– ACQ or CA treatment for all components because all components

were potentially exposed to soil or rain –long term

Prototype with untreated components. Photos courtesy of SNC Lavelin

Design plus Preservative Treatment

• Britco houses in Aceh inspected after 4 years

No evidence of insect attack. Minor instances of decay

Photo courtesy of Jim Creffield, Onwood Consulting

Without Preservative Treatment?

• Housing built in Aceh using untreated local materials attacked by termites after 6 months.– Source: representive of aid group

• Housing built in Haiti using imported material with treated sheathing and untreated framing– Not a good idea

Conclusions

• Fit design and treatment to local hazards• Simple design solutions can improve durability• Preservative treatment is needed vs. termites

– Deep penetration essential for termite protection• Most Canadian species resist pressure treatment• Diffusible/pervasive treatments are best• Borates as effective as CCA under cover• Tru-core process looks promising• Specify precisely• Quality assurance is critical

Any Questions

Technology

Sdrhcon2011 morris