Working under cover: several materials and methods for enclosing scaffolds and work platforms are available

Masonry Construction, Jan, 2003 by Jim Camillo

The phrase "undercover work" doesn't bring to mind images of a private detective in a fedora sleuthing in and out of the dark for the masonry contractor. Instead, these jobsite veterans see images of bricklayers and block layers on scaffolds or work platforms relying on plastic or fabric enclosures to protect them from inclement weather so that they can work productively.

This inclement weather can be rain or extreme heat, but to the contractor it is primarily cold, snow, and strong winter winds. Consequently, the winter enclosure is a major concern for masons in the northern United States and Canada.

However, the question of when a winter enclosure is required often depends on a number of factors other than ambient air temperature, with the most important one being cost efficiency. Who will pay for the protection: the masonry contractor or the general contractor?

Other important factors include job size and duration, number of workers, safety regulations, and proper mortar curing. Because of these many factors, masons and manufacturers agree that the winter enclosure is not always a "one-size-fits-all" issue. The protection requires job-specific equipment, materials, and installation methods to be most effective.

On the equipment side, work platform manufacturers usually have proprietary frames for their specific models. Scaffold manufacturers offer very few products for enclosure but will discuss the topic with contractors and make recommendations. Enclosure manufacturers offer a range of materials for use on both work platforms and scaffolds.

Masonry or general contractors almost always put up their own enclosures; however, there are specialty companies that perform this type of work. Masonry contractors who use outside services significantly reduce jobsite labor charges, but they must be sure to factor in the extra cost at the estimating stage so they do not lose money on the job.

The importance of being enclosed

An enclosed work area must do more than simply improve the comfort and efficiency of masons and tenders. The enclosure must also protect the wall being built, achieve temperatures high enough to facilitate cement hydration in water, and ensure a good bonding of mortar to the masonry unit.

James J. Adrian, Ph.D., P.E., C.P.A., Peoria, Ill., discussed the effects of cold weather on masons in his article "Construction Productivity: The Impact of Temperature." According to Adrian, a controlled study was done with masons building walls using standard CMUs in temperatures ranging from 40[degrees] to 100[degrees] F. The wind averaged 8 mph and the relative humidity was 60%.

Data from the study indicated that masons' output in these conditions was 60% of what it would be if they were working in 75[degrees] F weather. Or to put the difference another way, if the mason lays an average of 120 block per day in 75[degrees] F weather, he lays just 72 block in 40[degrees] F conditions. This study also addressed other winter work issues, such as proper clothing and equipment, overheating, exhaustion, and dehydration.

Masons should only use dry, frost-free masonry units and sand, which might require storage in a separate enclosed area. According to the Masonry Advisory Council's technical paper "Cold Weather Masonry," a masonry unit with a temperature below 20[degrees] F should be heated to a higher figure before installation. In ambient temperatures below 40[degrees] F, materials to produce mortar should be heated to between 40[degrees] and 120[degrees] F at the time of mixing. The mortar temperature should be kept above freezing until used in the masonry. (Optimum mortar temperature is 70[degrees] F, /-10[degrees], according to several industry sources.)

Packaged mortar materials should be securely wrapped with canvas or polyethylene tarpaulins and stored above the reach of moisture migrating from the ground. The Council's paper also notes the importance of installing wind breaks when velocities reach 15 mph and the ambient temperature is between 20[degrees] and 25[degrees] F, enclosing masonry under construction when the ambient temperature is below 20[degrees] F, and maintaining a temperature above 32[degrees] F within that enclosure.

It is extremely important to select the right enclosure system for the job. For example, are you laying a masonry veneer wall on an existing structure or laying a loadbearing masonry wall? A freestanding wall must be covered on both sides because there is no internal structure; consequently, a tent-type system might be most effective. In contrast, a contractor doing brick or block veneer work needs to protect just the exterior of the wall.

Effective material handling is another concern when working in an enclosed area. Contractors often load more mortar, brick, block, and stone on the scaffold or platform at one time to reduce the frequency of opening and closing the enclosure. They often move the material with wheelbarrows and carts instead of having enough area to place the materials at a specific spot with telehandlers and forklifts.