Saturday, June 7, 2008
Tuesday, June 3, 2008
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Figure 8.
Figure 7
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Figure 4
Figure 3
Figure 2.Figure 1.
Durable Trim For Coastal Construction
PVC trim holds paint well, resists rot, and looks just like woodby Jim Blahut
My company, Perennial Homes, works exclusively in the affluent community of Beach Haven, N.J., which is known for its attractive Victorian-era homes. As a design-build firm, our niche is building new homes with attractive exterior details like flat casing, window and door pediments, and wide corner boards. My customers value these exterior details, and we take pride in creating exteriors that retain a historic look. Our biggest problem in the past has been that the elaborate wood trim that gives our homes their Queen Anne style simply rots away on New Jersey's weatherbeaten coast. When composite and plastic trim became available several years ago, I thought it might be a good solution for the hardship of coastal weather and the limitations of wood trim. I hoped to find a trim product that wouldn't change the aesthetics of our popular homes and wouldn't require as much homeowner maintenance as painted pine or cedar. In our first attempt to find a long-lasting and good-looking exterior trim, we tried a hardboard-type composition product that promised lifetime durability and low maintenance. But it became apparent shortly after installation that the product had some limitations. Where the factory surface was disturbed from cutting or fastening, the material would swell, resulting in extra surface preparation by our painter. The hardboard's dimensional changes from wet weather and high humidity also made paint adhesion difficult (see Figure 1). Figure 1. This hardboard product started showing signs of swelling after a year, even though the manufacturer's installation instructions were carefully followed (left). The Azek's PVC composition has held up better and still looks good three years after installation (right). The next leg of our search led us to urethane, which has excellent dimensional stability and because of its composition should last a lifetime. But it wasn't right for us because it relies on its outer skin for an attractive appearance, and the exterior details on our homes require frequent ripping and machining of trim. When exposed, urethane's soft core looks a little spongy and inconsistent. For almost three years now, we've been using Azek (Vycom, Moosic, Pa.; 866/549-6900, http://www.azek.com/), which has held up well and retains the look of wood that our customers value. The PVC-based trim material is impervious to salt spray; it machines, cuts, and fastens like wood; and it's the only synthetic trim material we've found that can be machine sanded. We've been happy with Azek's performance so far, but it requires some special installation techniques to take full advantage of its durability and good looks. This is because its plastic composition behaves a little differently than wood. Special Techniques One of the drawbacks of plastic trim like Azek is its greater expansion and contraction compared to wood. On cold days, gaps can develop at unglued butt joints and miters. On long lengths of trim like corner boards or fascia, those gaps can be obvious, so we overlap joints with opposing 45-degree bevels, glue them with PVC cement, and put some construction adhesive on the back side (Figure 2). Figure 2. Because of PVC's tendency to expand and contract, the author uses extra nails and construction adhesive at joints so the gap will stay closed as the material moves. The adhesive securely attaches the joint to the house, and some extra nails at joints and board ends actually force the material to stretch in the center, preventing unsightly voids as the material shrinks. Intersecting trim (corner boards terminating in a frieze, for example) should have a gap of 1/4 inch for every 20 feet of length, so we leave 1/8 inch at each end to make the gap less noticeable. Gaps aren't a big deal high up on the house, but in more visible areas, like the bottom of corner boards, we back cut the bottom edge to further hide the gap (Figure 3). Without a little room to move, warm temperatures can cause the trim to expand and buckle. Figure 3. Gluing corner boards with PVC cement keeps joints tight and makes installation easier. The author's crew hides expansion gaps with a slight back-cut on the bottom of corner boards where ordinary gaps would be more obvious. Plastic materials also get brittle in cold weather, so poorly placed fasteners might create a crack, especially if temperatures are close to freezing. We keep nails 3/4 inch away from board edges and stagger them slightly. Staggering fasteners also reduces the likelihood of a crack along the line of fasteners as the material contracts and tension increases. Azek claims that its product won't yellow with age and doesn't require painting. Nevertheless, we always paint it because the brush strokes make it nearly indistinguishable from painted wood, and a couple of coats of acrylic-latex paint offer some additional protection from the elements. We use only 100% acrylic paints because they really stick to the material, and we prefer light colors rather than dark. Dark colors absorb more heat, resulting in greater expansion and softening of the material. Although we've experimented with darker colors and had good results so far, in climates warmer than ours they could result in saggy or bulging trim. It's best to stick with light shades or try dark shades before committing. Casing Windows We always preassemble our window casing in a four-sided frame in the shop and then install it on site in one piece over the window's nailing fin. Framing up the casing in this way has several key advantages. Using windows with a nailing fin creates a surface that isn't perfectly flat for trim. Because the fin is proud of the sheathing, casings tend to roll back toward their outside edge. Some builders put a thin rabbet on the back of the casing or shim the outside edge to match the thickness of the nailing flange. Both methods work, but preassembling the casing into a frame eliminates the additional step. Our method literally fuses the corners together with cement, which eliminates a source of water infiltration as well as gaps caused by cooler temperatures. Finally, cutting and assembling the casing gives us a foul-weather project when coastal storms prevent us from working outside. We start our casing process by making a cut schedule when the windows show up on site. I measure the frame and add about 3/16 inch to allow for caulking and contraction in cold weather. Large picture units get a little larger gap, and on twin and triple mulled units I add 1/16 inch for each additional window on top of the 3/16. I keep a file of measurements for future jobs; sometimes I have all the dimensions I need to make the frame assemblies without taking any new measurements. The assembly process is straightforward. I start with a scrap of 2-by screwed to my workbench, which helps me get a true right angle and provides backup for predrilling and running in screws. If I'm making a few frames of the same size, it's easier if the 2-by is cut to the same length as the inside width of the casing frame. I make certain that both ends of my scrap are cut square, and I build the casing around it, starting at the bottom. I glue all joints with Gorilla's low-odor PVC cement (Gorilla Glue, Hollywood, Fla.; 866/782-4583, http://www.gorillapvc.com/), which cleans up with water. The cement works the same as plumber's PVC cement and keeps everything nice and tight during changes in temperature. But just like plastic plumbing fittings, the pieces need to be held tight, because the PVC cement won't bridge even small gaps (Figure 4). Then, I predrill at an angle and fasten the pieces with galvanized deck screws to hold while the glue sets (Figure 5). Figure 4. PVC cement actually fuses corners together. This keeps corners tight and eliminates a possible source of water infiltration. Joints must be held together tightly with nails or screws while the glue sets, because the cement can't bridge gaps like other adhesives. Figure 5. The author predrills at an angle and runs in some galvanized screws to hold the assembly while the glue dries. A scrap of 2-by makes for a true 90-degree angle and provides backup for drilling and fastening. To make several frames of the same size, cut the 2-by to the same dimension as the casing's inside length. After both bottom corners are fastened, I move on to the top. Our typical detail includes a 4-inch side casing with a 6-inch head casing to better reproduce older architectural styles. I fasten the top in the same manner, running it over the cut end of the side casing. The head casing gets a small piece of 1-by stock mounted on top, meant to replicate a traditional wood drip cap (Figure 6). I rip this out of a larger piece of Azek and fasten it on the flat with some PVC cement and a brad nailer (Figure 7). Figure 6. The drip cap used here is meant to reproduce a traditional wood cap and is ripped from a larger piece of Azek. One of Azek's strengths is that it allows you to sand out saw marks and other imperfections; other products "fuzzed," melted, or created extra work for the painter. Figure 7. The author relies on the cement to bond Azek to itself. The fasteners simply keep everything tight while the glue sets. Here the author's crew places a few brads, keeping the cap in place while the cement sets up. We typically use preformed 1 1/4-inch copper drip cap, which adds a decorative touch, lasts forever, and helps to weatherproof the assembly. I cut the cap about 1 inch longer than the head casing and put a 1/2-inch bend on both ends. I just use my framing hammer (not a waffle face!) and a block of wood to make the bends. When we install the casing frame, we make certain to slip the copper drip cap behind the housewrap so any water that gets behind the siding will run out when it reaches the top of the window (Figure 8). Figure 8. Copper drip cap adds a nice touch to the completed homes. It's cut about an inch longer than the head casing and bent over the ends with a hammer on a block of scrap wood (above). The completed cap is slid up behind the housewrap when the frame is installed (left). We fasten the completed assembly to the wall with a pair of nails every 12 to 16 inches using a 15-gauge finish gun. The pneumatic finish nail's small wire size allows the material to move around with changes in temperature and reduces splitting. It also makes nail holes easy to fill and finish. After caulking and painting, the casing is indistinguishable from traditional wood trim, even under close inspection (Figure 9). Figure 9. After the preassembled casing is nailed in place over the window fin, the narrow expansion gap between trim and window is caulked. Although the manufacturer claims that the material can be left unpainted, two coats of acrylic latex leave subtle brush marks, for a thoroughly convincing "woodlike" appearance. As with any new material, there is a learning curve with Azek, and some different techniques must be developed. But we've found the effort to be worth it, and our customers are happy with the results. Jim Blahut, along with his brothers Don and Mike, owns Perennial Homes and builds in the Beach Haven community on New Jersey's Long Beach Island.
PVC trim holds paint well, resists rot, and looks just like woodby Jim Blahut
My company, Perennial Homes, works exclusively in the affluent community of Beach Haven, N.J., which is known for its attractive Victorian-era homes. As a design-build firm, our niche is building new homes with attractive exterior details like flat casing, window and door pediments, and wide corner boards. My customers value these exterior details, and we take pride in creating exteriors that retain a historic look. Our biggest problem in the past has been that the elaborate wood trim that gives our homes their Queen Anne style simply rots away on New Jersey's weatherbeaten coast. When composite and plastic trim became available several years ago, I thought it might be a good solution for the hardship of coastal weather and the limitations of wood trim. I hoped to find a trim product that wouldn't change the aesthetics of our popular homes and wouldn't require as much homeowner maintenance as painted pine or cedar. In our first attempt to find a long-lasting and good-looking exterior trim, we tried a hardboard-type composition product that promised lifetime durability and low maintenance. But it became apparent shortly after installation that the product had some limitations. Where the factory surface was disturbed from cutting or fastening, the material would swell, resulting in extra surface preparation by our painter. The hardboard's dimensional changes from wet weather and high humidity also made paint adhesion difficult (see Figure 1). Figure 1. This hardboard product started showing signs of swelling after a year, even though the manufacturer's installation instructions were carefully followed (left). The Azek's PVC composition has held up better and still looks good three years after installation (right). The next leg of our search led us to urethane, which has excellent dimensional stability and because of its composition should last a lifetime. But it wasn't right for us because it relies on its outer skin for an attractive appearance, and the exterior details on our homes require frequent ripping and machining of trim. When exposed, urethane's soft core looks a little spongy and inconsistent. For almost three years now, we've been using Azek (Vycom, Moosic, Pa.; 866/549-6900, http://www.azek.com/), which has held up well and retains the look of wood that our customers value. The PVC-based trim material is impervious to salt spray; it machines, cuts, and fastens like wood; and it's the only synthetic trim material we've found that can be machine sanded. We've been happy with Azek's performance so far, but it requires some special installation techniques to take full advantage of its durability and good looks. This is because its plastic composition behaves a little differently than wood. Special Techniques One of the drawbacks of plastic trim like Azek is its greater expansion and contraction compared to wood. On cold days, gaps can develop at unglued butt joints and miters. On long lengths of trim like corner boards or fascia, those gaps can be obvious, so we overlap joints with opposing 45-degree bevels, glue them with PVC cement, and put some construction adhesive on the back side (Figure 2). Figure 2. Because of PVC's tendency to expand and contract, the author uses extra nails and construction adhesive at joints so the gap will stay closed as the material moves. The adhesive securely attaches the joint to the house, and some extra nails at joints and board ends actually force the material to stretch in the center, preventing unsightly voids as the material shrinks. Intersecting trim (corner boards terminating in a frieze, for example) should have a gap of 1/4 inch for every 20 feet of length, so we leave 1/8 inch at each end to make the gap less noticeable. Gaps aren't a big deal high up on the house, but in more visible areas, like the bottom of corner boards, we back cut the bottom edge to further hide the gap (Figure 3). Without a little room to move, warm temperatures can cause the trim to expand and buckle. Figure 3. Gluing corner boards with PVC cement keeps joints tight and makes installation easier. The author's crew hides expansion gaps with a slight back-cut on the bottom of corner boards where ordinary gaps would be more obvious. Plastic materials also get brittle in cold weather, so poorly placed fasteners might create a crack, especially if temperatures are close to freezing. We keep nails 3/4 inch away from board edges and stagger them slightly. Staggering fasteners also reduces the likelihood of a crack along the line of fasteners as the material contracts and tension increases. Azek claims that its product won't yellow with age and doesn't require painting. Nevertheless, we always paint it because the brush strokes make it nearly indistinguishable from painted wood, and a couple of coats of acrylic-latex paint offer some additional protection from the elements. We use only 100% acrylic paints because they really stick to the material, and we prefer light colors rather than dark. Dark colors absorb more heat, resulting in greater expansion and softening of the material. Although we've experimented with darker colors and had good results so far, in climates warmer than ours they could result in saggy or bulging trim. It's best to stick with light shades or try dark shades before committing. Casing Windows We always preassemble our window casing in a four-sided frame in the shop and then install it on site in one piece over the window's nailing fin. Framing up the casing in this way has several key advantages. Using windows with a nailing fin creates a surface that isn't perfectly flat for trim. Because the fin is proud of the sheathing, casings tend to roll back toward their outside edge. Some builders put a thin rabbet on the back of the casing or shim the outside edge to match the thickness of the nailing flange. Both methods work, but preassembling the casing into a frame eliminates the additional step. Our method literally fuses the corners together with cement, which eliminates a source of water infiltration as well as gaps caused by cooler temperatures. Finally, cutting and assembling the casing gives us a foul-weather project when coastal storms prevent us from working outside. We start our casing process by making a cut schedule when the windows show up on site. I measure the frame and add about 3/16 inch to allow for caulking and contraction in cold weather. Large picture units get a little larger gap, and on twin and triple mulled units I add 1/16 inch for each additional window on top of the 3/16. I keep a file of measurements for future jobs; sometimes I have all the dimensions I need to make the frame assemblies without taking any new measurements. The assembly process is straightforward. I start with a scrap of 2-by screwed to my workbench, which helps me get a true right angle and provides backup for predrilling and running in screws. If I'm making a few frames of the same size, it's easier if the 2-by is cut to the same length as the inside width of the casing frame. I make certain that both ends of my scrap are cut square, and I build the casing around it, starting at the bottom. I glue all joints with Gorilla's low-odor PVC cement (Gorilla Glue, Hollywood, Fla.; 866/782-4583, http://www.gorillapvc.com/), which cleans up with water. The cement works the same as plumber's PVC cement and keeps everything nice and tight during changes in temperature. But just like plastic plumbing fittings, the pieces need to be held tight, because the PVC cement won't bridge even small gaps (Figure 4). Then, I predrill at an angle and fasten the pieces with galvanized deck screws to hold while the glue sets (Figure 5). Figure 4. PVC cement actually fuses corners together. This keeps corners tight and eliminates a possible source of water infiltration. Joints must be held together tightly with nails or screws while the glue sets, because the cement can't bridge gaps like other adhesives. Figure 5. The author predrills at an angle and runs in some galvanized screws to hold the assembly while the glue dries. A scrap of 2-by makes for a true 90-degree angle and provides backup for drilling and fastening. To make several frames of the same size, cut the 2-by to the same dimension as the casing's inside length. After both bottom corners are fastened, I move on to the top. Our typical detail includes a 4-inch side casing with a 6-inch head casing to better reproduce older architectural styles. I fasten the top in the same manner, running it over the cut end of the side casing. The head casing gets a small piece of 1-by stock mounted on top, meant to replicate a traditional wood drip cap (Figure 6). I rip this out of a larger piece of Azek and fasten it on the flat with some PVC cement and a brad nailer (Figure 7). Figure 6. The drip cap used here is meant to reproduce a traditional wood cap and is ripped from a larger piece of Azek. One of Azek's strengths is that it allows you to sand out saw marks and other imperfections; other products "fuzzed," melted, or created extra work for the painter. Figure 7. The author relies on the cement to bond Azek to itself. The fasteners simply keep everything tight while the glue sets. Here the author's crew places a few brads, keeping the cap in place while the cement sets up. We typically use preformed 1 1/4-inch copper drip cap, which adds a decorative touch, lasts forever, and helps to weatherproof the assembly. I cut the cap about 1 inch longer than the head casing and put a 1/2-inch bend on both ends. I just use my framing hammer (not a waffle face!) and a block of wood to make the bends. When we install the casing frame, we make certain to slip the copper drip cap behind the housewrap so any water that gets behind the siding will run out when it reaches the top of the window (Figure 8). Figure 8. Copper drip cap adds a nice touch to the completed homes. It's cut about an inch longer than the head casing and bent over the ends with a hammer on a block of scrap wood (above). The completed cap is slid up behind the housewrap when the frame is installed (left). We fasten the completed assembly to the wall with a pair of nails every 12 to 16 inches using a 15-gauge finish gun. The pneumatic finish nail's small wire size allows the material to move around with changes in temperature and reduces splitting. It also makes nail holes easy to fill and finish. After caulking and painting, the casing is indistinguishable from traditional wood trim, even under close inspection (Figure 9). Figure 9. After the preassembled casing is nailed in place over the window fin, the narrow expansion gap between trim and window is caulked. Although the manufacturer claims that the material can be left unpainted, two coats of acrylic latex leave subtle brush marks, for a thoroughly convincing "woodlike" appearance. As with any new material, there is a learning curve with Azek, and some different techniques must be developed. But we've found the effort to be worth it, and our customers are happy with the results. Jim Blahut, along with his brothers Don and Mike, owns Perennial Homes and builds in the Beach Haven community on New Jersey's Long Beach Island.
source:
Design guidance for structural steelwork
25 Jul 2007 By James Stagg
The headache of incomplete design information is to be addressed by a guidance document to save structural steelwork engineers expensive late design variations.
The British Constructional Steelwork Association (BCSA) has worked alongside the Association for Consultancy and Engineering (ACE) to develop a checklist of responsibilities for steelwork design projects. It is currently in talks with the Health & Safety Executive (HSE) regarding endorsement.
The Allocation of Design Responsi-bilities in Constructional Steelwork Projects is being drafted under the supervision of a steering group made up of main contractors, consultant engineers, structural engineers, the Steel Construction Institute (SCI) and insurers.
Marion Rich, director of legal and contractual affairs at the BCSA, said: "Steelwork contractors don't always receive all the information they require, for example, loading or sizing. They then have to make design decisions and calculations and there is an obvious cost associated with this."
Campbell Gillan, group managing director at steelwork contractor and fabricator Watson Towers, welcomed the initiative.
"Information that filters through to contractors sometimes leaves a lot to be desired. Currently, if you have a problem you have to go back to the drawing board and it can take time and money to get everyone together.
"If problems can be resolved at an early stage, then it will be better for everyone."
The document is due to be published in the autumn.
source:
http://www.contractjournal.com/Articles/2007/07/25/55706/design-guidance-for-structural-steelwork.html
25 Jul 2007 By James Stagg
The headache of incomplete design information is to be addressed by a guidance document to save structural steelwork engineers expensive late design variations.
The British Constructional Steelwork Association (BCSA) has worked alongside the Association for Consultancy and Engineering (ACE) to develop a checklist of responsibilities for steelwork design projects. It is currently in talks with the Health & Safety Executive (HSE) regarding endorsement.
The Allocation of Design Responsi-bilities in Constructional Steelwork Projects is being drafted under the supervision of a steering group made up of main contractors, consultant engineers, structural engineers, the Steel Construction Institute (SCI) and insurers.
Marion Rich, director of legal and contractual affairs at the BCSA, said: "Steelwork contractors don't always receive all the information they require, for example, loading or sizing. They then have to make design decisions and calculations and there is an obvious cost associated with this."
Campbell Gillan, group managing director at steelwork contractor and fabricator Watson Towers, welcomed the initiative.
"Information that filters through to contractors sometimes leaves a lot to be desired. Currently, if you have a problem you have to go back to the drawing board and it can take time and money to get everyone together.
"If problems can be resolved at an early stage, then it will be better for everyone."
The document is due to be published in the autumn.
source:
http://www.contractjournal.com/Articles/2007/07/25/55706/design-guidance-for-structural-steelwork.html
Panel manufacturers hit back at recycling claims
14 Nov 2007 By James Stagg
Insulated panel manufacturers have hit back at accusations that there are insufficient facilities available for the recycling of panels containing a blown insulation core.
The claims surfaced after a contractor in Scotland was found to be crushing panels alongside other demolition waste (CJ 31 October), apparently unaware of the ozone-depleting potential of panels containing hydrochlorofluorocarbons (HCFCs).
Since 2004, all insulated panels have been manufactured without any ozone-depleting substances (ODS) such as CFCs or HCFCs, and are classified as non-hazardous. But panels containing blown insulation manufactured before 2004 are likely to contain ODS and must be sent for treatment at refrigerator recycling plants.
In a statement, Kingspan said the panels remain some of the most thermally efficient solutions available and that HCFCs were used as a transition material because of their lower ozone depletion potential.
It continued: “There are currently only very small quantities of ODS containing panels entering the waste stream. However, as we reach the end of the next decade this will have changed and we need responsible solutions to the end-of-life disposal of these panels.”
A spokeswoman told CJ the company was actively seeking solutions to blown core panel disposal to cope with anticipated demand in the years to come.
She added: “Kingspan takes the issue of end-of-life very seriously and has been working with industry experts in waste management and disposal for over two years, including extensive research into the disposal of older insulated panels through the use of existing refrigerator recycling plants, which is our recommended method of disposal where viable.”
The company says it has successfully re-processed panels taken from four separate sites this year, including one project of over 7000m² of CFC-containing roof panels.
LYSAGHT® Cold Formed Sections
LYSAGHT® Cold Formed Sections
Product Description and Features
BlueScope Lysaght cold formed steel channels and angles are roll-formed from zinc coated and uncoated material. The strength of BlueScope Lysaght's cold formed sections has been increased from 240 and 250MPa to 300MPa for both the zinc coated and uncoated products, increasing the structural capacity of the steel channel and angle sections. These sections have many uses in the construction, general fabrication and home handyman fields.
· Many combinations of sections are possible
· Sizes of several plain channels enables them to nest readily
· Normal box sections are easily fabricated
· Machine controlled dimensions allow a neat fit and provide an easy method of assembly for sliding joints
· Able to be welded or bolted.
Common Uses of this product
Structural: Building frames, roof trusses, purlins and girts, fascias, floor framing, trestles, bench frames, gates, fences, cattle grids, television towers, scaffolds, tank stands, stands, stock crushes and pens, feed and crop drying fames, ladders, hand rails, shelving frames, machinery bases, mullions and lintels, exposed beams and columnsMechanical: car trailers, boat trailers, hoppers, truck and bus bodies, agricultural machinery, railway rolling stock, jibs, conveyor or crane frames, rail or other containers, pallets and storage racks, ramps, chassis, sign posts, supports or frames, materials-handling conveyors and racks.
Warnings
· Cold formed steel channels and angles will perform as specified if design, fabrication and fixing are in accordance with our recommendations
· If it is intended to use cold formed steel channels and angles in exposed situations within 1km of salt marine locations, or in severe industrial or unusually corrosive environments, please contact us.
Product Details
Physical Properties
Plain Channels
Tolerances
Web:
+ 2 mm -1 mm for LC 12730, LC 15230± 1 mm for all other sections.
Flange:
± 2 mm
Length:
± 15 mm
Method of CataloguingPlain Channels are denoted by the letters "LC". In the number following these letters, the first three digits indicate the nominal web dimension of the channel in millimetres. The last two digits indicate the thickness of material in tenths of a millimetre, eg. LC 03816 - Plain Channel, 38 mm x 1.6 mm.LC 05130 - Plain Channel, 51 mm x 3.0 mm.
Download LYSAGHT® Cold Formed Section Plain Channel Dimensions Table (78 KB)
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