Summary of cost commentary on SIP construction
(by Steve Andrews, Site Editor)
On October 12, we posted on SIP Talk the question "What is the best way to reduce the cost of building a house with SIPs? The topic attracted a lot of comment from builders, both directly to that question and under closely-related discussion threads. What follows is a summary of those comments, mostly in the author's own words, posted between Oct 12-31. While a number of the comments were made within more than one post, they are listed here under just one participant's comments. (User ID names are used in order to make it easier to find the full-length post should you choose to look it up. Here and there, comments from different posts by one author are included in a single section below.)
"First, you should understand that SIPS are fundamentally different than sticks structurally. Sticks collect and distribute small point loads with some welcome redundancy. SIPs are akin to shell structures that disperse loads continuously and more or less evenly over their entire surfaces. Knowledge of all these properties should be giving us superior buildings by design, not just stick translations."
- You can save money by working economically with standard panel dimensions to minimize waste during manufacture of the 'kit. I advise that you lower the top floor wall height to between 4 and 7 feet, depending on plan/headroom requirements, and go with cathedral or vaulted roofs/ceilings.If the building is only one story, dropping the top plate height to about 7 feet and vaulting the ceilings-but also being sure that the wall panels drop down outside the floor deck to bear directly on the foundation sill plate and insulate the rim band with insulated panel-allows the use of economical 8-foot panels.
- Use balloon framing, especially if you import a SIP-framing crew. "The panel crew barrels through, putting up the walls and then posting up the roof and then they're on to the next job. Local guys can do the interior framing."
- This allows interior framing with light-gauge steel, with its advantages:
- the steel framers do drywall as well, so that's one less trade to coordinate;
- no complaints by rockers about the quality of framing;
- the drywall must be screwed, so nail-pops are gone forever;
- mechanical trades appreciate the reduced need for drilling (lowering their price?);
- steel doesn't split, warp, twist, shrink, etc.;
- the shrink-resistance of steel makes it more compatible with SIPS.
- SIP construction lowers heat loss, which reduces the size of HVAC equipment and saves money. (Bill Chaleff)
- Start with the foundation! It seems I am always converting stick-built plans over to panels. Most plans are not designed to use the panel sizes effectively. A well-thought-out foundation that utilizes jumbo panels and takes into consideration the direction of the corner laps in the foundation plan would definitely affect the overall cost of the panel package."
- Try to locate mechanicals on interior walls.
- "In roof systems that utilize structural splines, assemble 2 or more panels together on the ground and lift the entire assembly into place in one lift..We are installing 8'x34' sections.averaging 1940 ft2 of panel a day...with a crew with very little or no SIP experience."
In Western New York we are competing with stickbuilt shells dollar for dollar right now."
"Have a panelized plan. Utilize shop labor; ie have the doors and windows cut out, framed and the panels numbered and splined [before they reach the site]. Get your own crew.My 6-man crew can frame a 2600 sq.ft. two-story in five days. The roof panels (4x16 to 4x28) go on in a day with a crane. Framing labor had been killing us, so we cut the cost in half by having our own crew; then we sub them out to stick-frame builders when we don't have a panel house to build."
"We make our profit from planning processes, prefabrication and erection profits, just as any other sub-contractor. All things considered, panels cost more than sticks and are approximately 60% faster to erect. Higher costs but higher quality, true and straight frame, no callbacks, lower labor costs-I get more for the same or less cost."
- "In California, an average wall panel costs $3/ft unfabricated, up to $5/ft2 fabricated. For roof panels, add approximately $1/ft2. Installation costs approximately $1.60 - $2.60/ft2 floor space and you still have to buy lumber.
- "The best roof set I have done was 2200 ft2 of 6/12-pitch roof in 6 hours, with a crane, one set-up man to hook the panels to the crane and three carpenters on the roof. I have also erected a 48'x48' home with 8-foot walls in as little as 1.5 hours. We did this with a crew of 15 volunteers who were the owners and their friends."
- Lower compensation insurance, fewer payroll taxes, less need for qualified labor-"all make a good argument to do the job fast and right the first time with SIPs. This is truly a great way to reduce [non-material] costs."
- Also, "when a designer, architect or engineer comes up against a problem with SIPs that he or she does not understand, they will revert to their experience with wood framing and standard load charts to solve the problem. But an architect who has studied the SIP product will help you in not over-sizing wood members or structural elements. So, what I consider to be one of the very best ways to cut costs when using SIPs is to use and architect or engineer who fully understands what a SIP can and cannot do!" (Ed Stahl)
A manufacturer, panel fabricator and builder all agreed on a point made above: that increased use of pre-cut panels cuts on-site time and associated costs. Therm: "The single best way to bring the cost of panels down is to deliver a finished product to the job site. The most expensive place to do work is in the field. A panel company that can deliver a complete system with all the elements of the shell included in the product before it reaches the site will naturally drive the cost down." Uziah: "This manufacturer is absolutely right about pre-fab panels." Panel Built: "Everyone who has made comments on this subject has talked about individual ways to bring down costs. The key is folding all those ideas and practices into one process. Fabrication companies that focus on volume sales can put all those ideas into practice. Higher sales volume allows a fabrication company to get very inventive in pricing structures for each individual project.We compete well with dinosaur stick-framed construction. Even when costs for SIPs are higher, you can show the client how that investment pays off within a 3-to-5 year period."
To wrap up: the point hammered home most frequently by participants in the discussion was that "SIP homes are better and have more value and should be priced accordingly." Yet the discussion itself reemphasizes that that there are ways to cut the cost of building with SIPs, from smart design right up through panel placement.