RESIDENTIAL CONSTRUCTION SPECIFICATIONS Guide

In This Article DIY Without detailed specs, you don’t really know what to expect in the finished project.
 

Construction drawings focus on a building’s shape, appearance, and dimensions, while the written construction specifications, or specs, focus on what materials will be used and how they should be installed. In general, the more detail in the written specifications, the better. Without detailed specs, you don’t really know what to expect in the finished project. Learn More Schedule 15 Consultation
 

What information goes in written notes on the drawings, and what goes in the specifications is up to the designer, but a good set of detailed specs goes far beyond what could possibly be put into a drawing. It’s OK if the same information appears in both places, but if there is a contradiction, the specifications generally take priority, at least legally.

At a minimum, building specifications list what materials to use, and call out any special installation requirements. Specs are much more valuable if they go further and provide detailed installation requirements and establish quality standards for the materials and the workmanship. Equally important is providing a measurable way to determine whether the work has met the standard. This will prove valuable if there are any disagreements over the quality of the work.

On a large job, the specs will be broken down by trades, so there will be specs for the painting, roofing, concrete work, flooring, and so on. 

Many construction jobs are done with no or minimal written specifications. The customer doesn’t really know what he or she is getting, and often is often disappointed with the results. In the absence of a written spec, you will often get so-called “builder’s grade” products, a euphemism for cheap and basic. Builder’s-grade windows are typically solid vinyl with very cheap screens that are difficult or impossible to remove without breaking them – I know, as I have some in my current home and previous home. Builder’s-grade doors, floor coverings, tubs, showers, bathroom fixtures, and cabinets share the same minimal price and quality.

If you want better, and if you want to know ahead of time what you are getting from a contractor, you need at least  basic written specifications, identifying the products that will be used, how many coats of paint or floor finish you are getting, and so on. Otherwise, it’s a complete crap shoot. If you are working with a quality-minded, conscientious contractor, you may get an excellent job, but why leave it up to chance? Learn More Schedule 15 Consultation

You can’t and don’t want to spec every nail. But reasonably detailed specs will reduce your risk of getting substandard materials or workmanship, and it will reduce the risks of disputes over the completed work quality since the standards for material type, quality, and workmanship are spelled out in black and white.

How detailed a spec should be depends on the complexity and requirements of the job. I’d recommend basic specs, such as listing the products to be used by brand and model for just about every product and material to be used on the job. For paints and coatings, you will want to know what prep work will be done and how many coats applied.

Beyond that, you’ll want detailed specs for portions of the job that are very costly (or costly to fix, such as the foundation), critical to the success of the project,  prone to problems (like radiant floors), or require specialized products or workmanship that may be unfamiliar to the tradespeople doing the job. If problems show up after the work is done, you will be in a much stronger position to get the work repaired if you have a written spec to fall back on. Examples of products or systems that should have detailed installation specs, and issues to cover in the specs, include:

• Foundations – Concrete mix, strength, reinforcing
• Concrete slabs – Concrete mix, strength, reinforcement, flatness, finish, expansion/movement joints, allowable cracks
• Roofing – Type, weight/thickness/warranty period of roofing; type of underlayment, flashing, and fasters. Carefully spec details for low-slope roofs, and for complex roofs with hips and valleys, detailing how valleys will be waterproofed. Get detailed material and installation specs for roofing materials such as wood, metal, tile, slate, and composite materials.
• Windows and doors – Specify type, model, and energy efficiency. Also provide flashing details around doors and windows to prevent leaks, which are common here.
• Skylights – Prone to leaking. Make sure installation follows manufacturer’s specs. Extra membrane flashing around skylights recommended in freezing climates.
• Insulation and air sealing – If you care about energy performance, you’ll need to spec this carefully.
• HVAC systems – A lot can go wrong here. System can be oversized, undersized, uneven, noisy, leaky (ductwork), and inefficient due to installation errors.
• Radiant heating – Needs careful specifications by an experienced designer or installer.
• Wood flooring – Moisture content, substrate, fasteners, vapor barriers (over slab), finishes. Follow the recommendations of the National Wood Flooring Association (NWFA).
• Ceramic tile – Follow the methods and standards in the TCNA Handbook if you want trouble-free installations. Floor must be stiff enough. Also pay attention to substrates, adhesives, and movement joints.
• Special construction for wind or seismic loads: This includes wind-resistant roofing, impact-resistant windows, engineered framing fasteners, and shear wall requirements.
• Metal components in coastal areas: Make sure that any exposed metal flashing, fasteners, or hardware is stainless steel, copper, brass, lead, or double hot-dipped galvanized. Other metals and finishes will not last long due to the corrosive power of salt spray.

Over the years, I’ve learned to assume nothing about a job where the scope of work is not in writing. If the work description or construction drawing is not specific, you won’t really know what you’re getting until the job is done. You may be happy with it – or not, but changing it mid-job or after completion is always expensive and who will pay for the changes will always be contested.

If you know what you want, specify it. Do you want the nail holes filled with a color-matched putty on your natural woodwork – if so, put it in the contract. Otherwise you might find yourself filling several hundred holes by yourself after the job is “done.”

While you can’t spec every last nail, there are times when you have to spec things as small as nails. For example, I once built a gambrel roof using site-built trusses fabricated with plywood gussets. The nails in the gussets had to be a specific size, length, and number, and installed in a specific pattern for the engineered design to work. Using the proper type and size of nails and fasteners is also critical in truss hangers and other engineered framing connectors, as well as with tile backerboards, drywall (to prevent nail pops), and many other building materials.  So, in many cases, it does make sense to specify the nails.

TYPES OF SPECIFICATIONS

Specifications may cover the properties and installation of products and materials, and systems. They are either written as product specifications, installation specifications, or performance specifications.

Product specifications. These can name specify a specific brand-name product, such as: “Foundation insulation shall be 2-inch tongue-and-groove Dow Styrofoam, or equivalent.” To give the contractor more flexibility it may provide a technical spec, such as  “Rigid foam insulation to be 2-inch-thick extruded polystyrene with tongue-and-groove edges, with a minimum compressive strength of 25 psi.”

The first type of spec, that names the product is certainly the simplest – no question about what is to be used. Language such as “or equivalent” or “or similar” are OK as long as you state in your contract that any such substitutions must be “approved by owner or owner’s representative.” In some cases, like with extruded foam insulation above, all major brands are pretty much the same. With other types of products, such as  paint, doors and windows, siding products, and composite wood products, equivalency is harder to determine. You’re better off finding the product you like and specifying just that. Learn More Schedule 15 Consultation

Highly technical specs are probably overkill for most residential products, except in high-end jobs, and in instances where the design or code calls for specialty products. For example, if you are putting Styrofoam insulation under a slab or foundation, you will need a higher compressive strength than what is typically found in the lumberyard. If you are in an area where the code requires impact resistant windows, wind-resistant roofing, or special structural connections to protect against earthquakes or high winds, then technical specifications are essential.

Installation specifications. Most contractors and tradespersons have their own way of doing things. In the building trades, you’ll often hear things like “This is how I’ve always done it” and “I’ve always done it this way and haven’t had any problems.” That’s exactly what the contractor told me who installed a Velux skylight in a shallow roof, violating the manufacturer’s specs, and guess what – it leaked until I removed it and reinstalled it per the manufacturer’s instructions.

Unfortunately “the way we’ve always done it” may not work anymore due to changes in materials, codes, energy standards, or other factors particular to your job. The goal of installation specs is to avoid these kinds of problems. These describe, in detail, how a product is to be installed or applied. For example,

Install 2-inch Styrofoam extruded polystyrene insulation over interior side of basement wall by attaching wood furring strips vertically over the foam insulation at 16-in. or 24-in. on center. Fasten 1×2-in. or 2×4-in. furring strips through the foam insulation and into basement wall using Tapcon or similar screws that penetrate about 1-1/4″ into the concrete wall. Use 4 screws per 8 ft. furring strip.

Quality standards. Installation specs for visible finish work often contain quality standards as well (see also Quality Standard contract language). Quality standards are only useful if they provide an objective, measurable way to determine if the standard has been met. For example, a Level 4 drywall finish, from US Gypsum, based on the standards of the Gypsum Association is as follows:

All joints and interior angles shall have tape embedded in joint compound and shall be immediately wiped with a joint knife or trowel, leaving a thin coating of joint compound over all joints and interior angles. In addition, two separate coats of joint compound shall be applied over all flat joints and one separate coat of joint compound applied over interior angles. Fastener heads and accessories shall be covered with three separate coats of joint compound. All joint compounds shall be smooth and free of tool marks and ridges. The prepared surface shall be covered with a drywall primer like Sheetrock first coat prior to the application of the final decoration.

While this goes into great detail about the installation, the only standard about the quality of the visible finish is that the joint compound should be “smooth and free of tool marks and ridges.” How smooth and free of tool marks is pretty vague.

A better quality standard is provided by the National Association of Homebuilders (NAHB) in their book of Residential Construction Performance Guidelines. This provides both performance guidelines and corrective actions. For drywall finish to meet their standard it must not have any of the following:

• Any joints visible from a standing position, facing the surface at a distance of 6 feet under normal lighting conditions
• Any nail pop, blister, or other blemishes that are visible from a standing position facing the surface at a distance of 6 feet under normal light conditions
• Any drywall cracks greater than 1/16 inch in width
• Any defects resulting in cracked corner bead, trowel marks, excess joint compound, or blisters in tape

This seems like a reasonable standard, although I’d apply the same standard to cracks as to other defects: Any drywall crack visible from 6 feet under normal conditions should be fixed.

Performance specs. This type of spec describes the standards that must be met, rather than the specific product of system to be used. The contractor will propose a product or system, which must then be approved by the owner or owner’s representative, such as an architect or construction manager.

Performance specs are often used for heating, air conditioning, and other mechanical systems. They may also be used for wells, septic systems, or other building components where the performance is more important than the specific products and materials used. In general, this is a practical and economical approach that puts the responsibility on the subcontractor or vendor to design the system. They have the expertise to do this efficiently and are accustomed to putting out proposals. They may offer some suggestions that differ from your specs, which are generally worth listening to.

A performance spec for an air-source heat pump might read:

Air-source heat pump shall cool all rooms in the house to 76°F degrees in cooling season with outdoor temperatures of 93°F, and heat all rooms in winter to 70°F with outdoor temperature of 25°F. First and second floor shall have separate heating and cooling zones. All ductwork to be galvanized sheet metal or insulated duct board, fabricated, sized, and installed in accordance with applicable ASHRAE and SMACNA standards. All ductwork joints shall be sealed with duct mastic (and fiberglass tape on ductboard). All ductwork in unconditioned spaces shall be insulated.  Heat pump to be Energy Star certified. Learn More Schedule 15 Consultation