Post on 20-May-2015
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
Design Solutions for Durability
Vapour/air barrier on the inside
Moisture Management
Moisture ManagementVapour Control inTropical Climates
Design Solutions for Durability
Vapour/air barrier on the outside
Design Solutions for Durability
• 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
Design Solutions for Durability
• 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
Integrated Termites Management : The 3Ss
Slab/foundation
Structural
durabilitySite
management
Slab/foundation
Disaster Relief
Slab/foundation
Integrated Termites Management : The 3Ss
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
Preservative Treatment Options
Must consider• Regulations in exporting country• Regulations in importing country• Potential for human contact• Building design• Wood species• Local decay and termite hazards
Preservative Treatment Options
• 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
Preservative Treatment Options
• 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
Preservative Treatment Options
• 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
Preservative Treatment Options
• 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
Preservative Treatment Options
High-density Incised White SpruceIncised white spruce Incised Pacific Silver fir
Preservative Treatment Options
Termites eat through a thin shell of treatment
Preservative Treatment Options
Termites give up if treated shell is thick enough
Preservative Treatment Options
Or, if they get through, the box is strong enough
Preservative Treatment Options
• 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?
Preservative Treatment Options
• Got boron ?
Borates have a positive perception
600mm
400mmm
1000mm
Preservative Treatment Options
Above ground protected termite test
Preservative Treatment Options
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
Preservative Treatment Options
• 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
Preservative Treatment Options
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
Preservative Treatment Options
Treatment results on BC SPF (pine)
Red colour with reagent shows penetration
Preservative Treatment Options
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
Preservative Treatment Options
• 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
Preservative Treatment Options
• OSB Treated with ZB During Manufacture
Data courtesy of Peter Laks, Michigan Tech University
Preservative Treatment Options
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
Preservative Treatment Specifications
• 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
Preservative Treatment Specifications
• 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