Construction Window Cleaning Basics

Construction window cleaning includes the removal of several types of construction debris from glass surfaces, including plaster, stucco, concrete, paint, texture, taping mud, mortar, silicone, stickers, and tape. Removing this debris without scratching the glass is the real challenge of construction window cleaning.

This article covers techniques and recommendations in meeting this challenge (it does not cover ladder use, which may be required). Note: Many of the topics covered in this article are also addressed in the video Construction Window Cleaning Basics.

Prior to Starting any Construction Window Cleaning

Before signing a contract or starting any construction window cleaning, it is highly suggested that you examine the entire project. A pre-contract inspection should give you a good idea of what to expect. You must always ask yourself, "Can the windows be cleaned without scratching the glass?" If not, this should be discussed with the builder before signing a contract.

It is also important to know your capabilities and the capabilities of your crew before attempting to take on a construction window cleaning project. Never consider excepting a window cleaning challenge a builder is proposing if you are not 100% confident you can remove all construction debris without scratching the glass. If windows are covered with excessive construction debris, you should consider the possibility that the glass is already scratched.

Most builders require their subcontractors to protect the home from the effects of their trade and to clean after themselves. Check other subcontractors' contracts to understand their responsibility for window protection during the entire construction process. Always keep in mind, you will likely be the first person the builder comes to for the replacement cost of any scratched glass.

Lastly, it is vital to get any liability agreements or waivers in writing, prior to starting any construction window cleaning. Especially important is an agreement covering liability for existing scratches, scratches caused by others, and scratches caused as a direct result of defective tempered glass. Listed below are some sample liability waivers (in PDF format). Sample waiver between window cleaner and builder Sample waiver between builder and supplier Note: Defective tempered glass is covered in more detail in the Glass Quality section of this site.

Required Tools

Before we can cover the proper procedures, it is important to make sure that you have the necessary tools. They are as follows.

  • Soaps, acids and chemicals
  • Bucket
  • Squeegees (2 sizes, 14" & 8")
  • Holsters and belt for tools
  • Scraper (Razor or broadknife)
  • Razor blades
  • Small angled putty knife
  • Green nylon pad
  • Sponges
  • Rags
  • Window brush or stripwasher
  • 12" flat fine mill file (for sharpening broadknife)
  • Strip Washer or Window Brush?

Due to the high amount of construction debris found in most construction window cleaning situations, we do not recommend using a strip washer. This debris can easily get caught in the strip washer, and result in scratching the glass. This is not as likely in a window brush as the bristles do not cling to the debris the same way the shag of the strip washer does. It is also much easier to clean this debris from a window brush. These issues, along with the fact that it can hold far more water, make the window brush the clear choice for construction window cleaning purposes.

Razor Scraper or Broadknife?

Razor scrapers are by far the most popular tool for safely removing construction debris from glass, without scratching. However, there are a number of drawbacks to razor scrapers.

  • A razor scraper comes with a risk of serious injury to its user.
  • Razor scrapers have limited use on heavy plaster and concrete, and frequent blade replacement is required as a result.
  • Overnight storage of razor scrapers must be examined for iron oxide (rust) prior to reuse. Because rust on the blade of a razor scraper will scratch glass, razor blade replacement is required if any rust is present.
  • Aside from the inconvenience and time loss related to frequent blade replacement, there is also the issue of high replacement costs for the physical blade itself.

Prior to the development of razor scrapers, broadknives were the scraper of choice for removing construction debris from glass. This method has been employed for over 40 years, and brings with it some of the following benefits.

  • Broadknives have a far reduced risk of injury to its user compared to a razor scraper.
  • Broadknives are very durable and work well to remove heavy plaster and concrete from glass, without as much damage to the scraper.
  • Replacement cost for a broadknife is $6-8 and is only required about once per year.
  • If a broadknife is damaged or gets dull, it can be easily resharpened with a fine mill file. The choice between a razor scraper and a broadknife is one that depends on the situation and your personal preference. However, the durability and safety associated with a broadknive, combined with the inherent risk and cost of replacement of a razor scraper, makes the broadknive our tool of choice.
Soaps, Chemicals, and Acids

The use of soaps and chemicals can greatly assist in the window cleaning process. However, it is important that you know which product to use in which situation. Listed below is some information to assist in this selection.

Soaps

The selection and use of soaps in window cleaning applications is often misunderstood and overcomplicated. For most window cleaning projects, soap is not a key issue. Only use soaps that you know will help in the process. Sometimes, no soap is better than too much soap or the wrong soap. Rarely is more soap better. It's important to first select which type of soap to use, and then determine the amount to use. At Fields CSI we use Fields WPR, a soap that is manufactured for us. However, many window cleaners use dishwashing soap, which is usually sufficient for normal paint removal.

Chemicals and Acids

When encountered with more than just paint and dust on the window, many times it is necessary to use chemicals to aid in cleaning the glass. We use Fields Scale Remover, a product that is manufactured for us. It is used to loosen plaster, stucco and concrete from the glass surface, prior to scraping. This product will also remove the film (effervescence from cement) that runs down the glass during and after plastering exterior walls. Fields Scale Remover contains phosphoric acid, a key ingredient in the removal of concrete, plaster and mortar from glass. Products containing phosphoric acid help dissolve the cement in construction debris and make it much easier to remove. Any chemicals or acids you decide to use should be tested to be safe for human use, the building exterior, and the IG (Insulated Glass) seals.

The Construction Window Cleaning Process

Start off by filling your bucket 2/3 full with water. The more water you have in your bucket, the cleaner the water will stay. If you have sponges that have soap in then from a prior use, now is the best time to remove it. The best way to accomplish this is by squezing the sponge a dry a possible. Then, while still squezing the sponge, submerge it in the bucket of fresh water and release. Once the sponge has filled with water, remove it from the bucket and squeze it out, making sure that the water does not go back into the bucket. Repeat these steps as needed. If your application requires the use of soap, add the soap after the bucket is filled to prevent suds.

If you have chosen to use a broadknife rather than a razor knife, now is a good time to sharpen the knive. When sharpening a broadknife, the goal is to create a smooth, squared-off end. The knife should not be sharp to the touch, but the faces of the knive should come straight down and meet the edge at a 90° angle. Using a towel under the file can help smooth out the sharpening. Next, sharpen the small angled putty knife for cleaning window frames. Always clean scrapers prior to sharpening to prevent rust and debris from contaminating the file. Keeping the file clean can greatly increase the life of the file.

Note: Razor scrapers can be used in place of a broadknife.

Cleaning Inside Windows

Whenever possible, the inside windows should be cleaned before the outside windows. This is advised because the cleaning of the inside window will require opening and closing the window, which could result in leaving streaks on the glass. It is also advised that the window tracks be vacuumed prior to cleaning the window. With this in mind, here are the steps to cleaning the inside windows.

  1. Wet entire window, frame and track with window brush.
  2. Remove any stickers with a small razor blade, while glass and frames are soaking.
  3. Clean window frames and tracks with the little angled knife in one hand and the green nylon pad in the other. The green pad should be kept wet at all times. It is important that the green pad never touch the glass, as it will scratch. Also, avoid contact between the green pad and textured window jams so as not to remove any of the texture.
  4. Remove all excess texture and taping mud (if any) from glass with scraper. Use single upward motions and throw into empty bucket.
  5. After excess texture is removed, rewet glass with window brush.
  6. Start scraping the glass with the window brush in one hand and the scraper in the other. Scrape the glass nearest to you first to prevent splash back. When scraping, have a pattern or system to cover every inch of the glass. The method we use starts with a stroke across the top, and then down the right side. We then go back to the top of the window, where we work down in rows, from right to left.
  7. After glass is entirely scraped, rewet glass with window brush.
  8. Sponge down window frame and tracks. Touch up the frames with green pad and angled knife, if needed.
  9. Sponge down perimeter of glass, prior to squeegeeing.
  10. Squeegee the window nearest to you first. If you start with the window farthest from you, it is likely you will splash water onto the finished pane while squeegeeing the window nearest to you. On hot days, you may need to rewet the window. In construction window cleaning we choose not to fan squeegee our windows because the windows are usually too small. Also, sand and other debris could be a problem with this method.
  11. Sponge out window track, if there is one.
  12. Touch up glass and frames with rag as needed.
Cleaning Outside Windows

If the outside of the building is stuccoed, we recommend using Fields Scale Remover (or any suitable product with phosphoric acid) to assist in removing stucco and concrete from glass and frames. The process for cleaning exterior windows is similar to that for cleaning interior windows. The process is listed below.

  1. If stucco is present on the glass, run a stream of Fields Scale Remover (or other phosphoric acid) across the top of each window before wetting the glass. As it runs down the glass, spread over entire surface with a slightly wet window brush. DO NOT let acid run down stucco.
  2. Wet your window brush again and wet the entire glass, and frames if needed.
  3. Remove any stickers with razor blade, while glass and frames are soaking.
  4. Clean window frames and tracks with the little angled knife in one hand and the green nylon pad in the other. As discussed above, make sure that the green pad does not touch the glass.
  5. Rewet the glass and start scraping the glass with the window brush in one hand and the scraper in the other. Again, scrape the glass nearest to you first to prevent splash back.
  6. Rewet glass with window brush.
  7. Sponge down window frame and tracks. Touch up the frames with green pad and angled knife, if needed.
  8. Sponge down perimeter of glass, prior to squeegeeing.
  9. Again, squeegee window nearest to you first to prevent splash back. On hot days, you may need to rewet the window. In construction window cleaning we choose not to fan squeegee our windows because the windows are usually too small. Also, sand and other debris could be a problem with this method.
  10. Sponge out window track, if there is one.
  11. Touch up glass and frames with rag as needed.
GLASS RESTORATION

Our restoration service includes a process by which the scratch is ground out of the glass, and then polished to a factory quality finish.

Contractor Services

We have since expanded our services to focus more on surface restoration of various substrates, including glass restoration and much more.

Bird Control

We have expanded our restoration service to include other services, such as granite restoration, window frame repairs, and more.

CONSULTATION

We help determine the causes, prevention and possible liability for glass replacement or its restoration.

Training

Our seminars cover a wide variety of topics to include: Safety precautions during the restoration process, customer expectations, and more.