Concrete Foundations

How do you seal concrete foundations?

A strong house foundation is necessary when tackling any construction project. While many precautions are taken to ensure that a foundation will hold up for the lifetime of the house that’s set upon it, sealing a foundation is one of the most important aspects of keeping it functional over the long haul. If sealing is done improperly, moisture that enters the home through the foundation walls and floor can lead to problems such as mould growth and can contribute to a variety of health problems. Knowing more about sealing a foundation can help you understand not just the problems that can occur if it’s done wrong, but also what you can do to fix problems that already exist in older structures.

Moisture is a serious threat to the longevity of your home. In the form of rainwater and ground seepage, it can ruin foundations, windows and doors, masonry and cement, siding and roofs. Excess moisture can also create serious mould problems and is quite common in basements and crawl spaces. However, it can occur above ground as well, due to roof and gutter leaks. Sealing out moisture and waterproofing your home is the most important maintenance chore you can do.

Moisture is the biggest culprit to the longevity of your home. In the form of rainwater and ground seepage, it can ruin foundations, windows and doors, masonry and cement, siding and roofs. Excess moisture can also create serious mould problems and is quite common in basements and crawl spaces. However, it can occur above ground as well, due to roof and gutter leaks. Sealing out moisture and waterproofing your home is the most important maintenance chore you can do.

We have a wide range of external waterproofing services at Hitch Property Constructions.

Foundation Sealing in a New Structure

The bottom line is that sealing a foundation is a different process in different parts of the country. Soil composition, annual rainfall levels, and annual temperature changes all play a role in how sealing is done in your area.

In general, moisture and soil gases can be eliminated by specific construction techniques and materials. Often a special mastic coating and drainboard are applied to the exterior of the foundation wall. At the foundation footing, drain tile is installed so that the water will run down the drainboard and drain away from the house. Gravel fill is used beneath the slab with a poly membrane, or vapour retardant, sealed over the gravel before pouring the basement floor. The poly is sealed at the edges and seams preventing moisture, radon and other soil gases from migrating into the home.

 Concrete Foundations

Sealing a Foundation That Is Already Damaged

Where people building a home shouldn’t have to worry too much about cracks and gaps in their foundation (as long as their contractor knows what he or she is doing and is familiar with the particular obstacles your area’s environment poses), owners of older homes often have to deal with foundation repairs that stem from obsolete building techniques and problems that have been neglected by previous owners.

There are several causes for cracks in a foundation, and some of them can lead to extremely costly and involved repairs in the future. Suppose you notice cracks in your foundation or other common symptoms of foundation problems such as windows and doors becoming misaligned or sloping floors. In that case, it is a good idea to hire a structural engineer to have a look at the problem. If you try and seal these cracks or gaps yourself before letting a professional examine them, you might only be making the problem worse by obscuring it.

Of course, you can hire a contractor to do the work right off the bat, but remember if you ask a handyman to come in and plug the cracks, you might only be getting a temporary fix to a more serious problem. The reasons why foundation sealing is necessary are often not as simple as they seem, and getting a proper diagnosis from a structural engineer (one who has no interest in the repair process and is only there to tell you what the existing problems are and what needs to be done to maintain the structure’s integrity) is the first step in a successful repair. Once your foundation has been thoroughly inspected by a professional and determined that the cracks and gaps need to be filled to prevent any further damage, there are several caulks, foams and other fillers on the market that you may be able to use yourself to do the job.

How To Waterproof A Foundation

Scheduling and Planning For Concrete Waterproofing

Allow considerable float time for waterproofing. If you’re using a waterproofing subcontractor, recognize that good waterproofers can be in high demand during the busy season. Rain can also delay waterproofing work.

Plan the layout of waterproofing well ahead of time. The plan elevations will likely show the finish grade line on the foundation walls, but these lines should be confirmed with the architect, if necessary. You don’t want black, gooey waterproofing showing above grade. Watch for changes in the level of grade. A line of waterproofing descending at a diagonal from one level to another won’t work if the architect has decided to handle the change with a retaining wall.

Construction Tips

Ideally, you should mark layout lines with a crayon or chalk line, especially on a complex foundation with varying grade. On a simple foundation, it might be safe to instruct the waterproofer to keep his work so many inches from the top of the foundation. I like to see waterproofing as close to finishing grade as possible, but no lower than 6 inches in any case. Don’t leave form-tie holes that are below grade unprotected. Work out ahead of time what you’re going to do at basement windows and bulkheads, porch foundations, and intersecting walls that don’t have to be waterproofed.

When deciding what walls get waterproofed, follow this basic rule: Waterproof any foundation wall that has earth on one side and usable space on the other, including crawl spaces. Extend waterproofing at least 12 inches onto intersecting walls that don’t have to be waterproofed. You might want to continue the waterproofing on other walls if it’s a very wet site. Under extreme conditions, water has been known to travel through the keyway along the footing and into occupied space. Consult with the architect if you have any doubts.

Check the waterproofing manufacturers literature for temperature limitations. You’re probably okay applying waterproofing on a cold day if you’re working with a solvent-based material. But watch out if your material is water-based. The lower limit for some products is 40F.

Waterproofing Curing Time

Likewise, check the manufacturer’s requirements for concrete curing time. For every sheet membrane I know of, concrete must be cured a minimum of seven days before membrane application, sometimes even longer. This is because the concrete will continue to dry long after it’s poured. The water vapour escaping from the concrete can prevent the waterproofing material from bonding. Concrete curing times for liquid membranes also vary considerably. Some require 14 days or longer. Others can be applied as soon as the forms are removed.

Protecting In-place Waterproofing

Most waterproofing systems need protection during backfilling. Some manufacturers have their protection board for this purpose. A drainage mat or insulation can also function as a protection board. An inexpensive 1-inch-thick expanded-polystyrene-foam board works fine as a basic protection course. However, one manufacturer has a protection board that functions as insulation, protection board, and drainage medium in one.

When adhering a protection board, make sure to use an adhesive that’s compatible with the waterproofing membrane. I’ve seen some adhesives eat right through waterproofing material. Besides providing protection during backfilling, you should protect waterproofing work that is in place from damage by other workers and trades. Keep workers from tracking across exposed membranes on footings, decks, or other horizontal surfaces. Don’t expect others to be as sensitive as you are to the importance of waterproofing.

Add Some Color

If you prefer to add colour, you can use Thompson’s Concrete Care 100-percent Acrylic Latex Stain. It can be used on any exterior or interior concrete or masonry surface, and provides a long-lasting, scuff-resistant coating that protects against flaking and peeling, prevents water damage and can be used on any exterior or interior concrete or masonry surface. It comes in a variety of fade-resistant colours.

Due to the nature of concrete, it’s extremely important to properly prepare the surface. Clean the surface as necessary, using the concrete cleaner and degreaser. If staining a smooth concrete surface, it may be necessary first to use Thompson’s Concrete Care Pre-Stain Etch. This will create a texture similar to 80-grit sandpaper. Make sure to sweep and rinse away all dust created by the etching process. Do not apply in direct sunlight or on hot days. Apply using an exterior paint pad, brush, roller or compression driven sprayer set for low pressure. Keep the leading edge wet and distribute the stain evenly. This will help avoid lap marks and keep the colour uniform.

Looking for external waterproofing Melbourne? Check out Hitch Property Constructions.

Waterproofing Safety

Waterproofing below grade can be dangerous. Because of the hazards, it’s usually not a good idea for anyone to waterproof alone. If you’re using a waterproofing subcontractor, make sure workers follow a written safety program and comply with hazard-communication requirements. Keep other trades and workers well away from the waterproofers work area.

Once you learn how to work with waterproofing materials, you can make good time without sacrificing safety. Here are some primary safety concerns that go along with waterproofing.

Flammable materials 

Many waterproofing products are solvent-based. Keep fire, smoking materials, welding operations, cutting torches, and other sources of ignition well away from the area.

Respiration hazards 

Use the manufacturer-recommended respirator, especially with solvent-based materials. In a close area, you might need an air-fed respirator. Don’t be complacent about this. Solvent vapours are deadly, and a large surface area of newly applied material can put out a lot of vapour. The vapours are usually heavier than air, so they tend to build up in a recessed area like a foundation excavation.

Skin injuries

Waterproofing materials can contain all sorts of chemicals that can harm your skin. As needed, wear protective clothing and gloves. When cleaning tools in a solvent, wear chemical-resistant gloves.

Injection hazards 

Take precautions when working with or around spray equipment. A high-pressure airless sprayer can inject toxic chemicals directly into your blood-stream.

Eye injuries Wear protective glasses or goggles as needed, especially when working with liquids.

Surface Preparation Procedure

Don’t skimp on surface preparation. You must get the foundation wall and footing clean, free of loose material, and fairly smooth. Do as much as you can ahead of time: Once you start waterproofing, rhythm is crucial, and you don’t want to have to stop to scrape loose concrete from the footing or break off a form tie.

Waterproofing materials aren’t designed to cover large voids or honeycombs. You’ll need to fill these, preferably with non-shrink grout or a good patching cement. You may be able to patch form-tie holes or smaller voids with trowel-grade mastic. Check the manufacturer’s instructions to make sure that whatever material you use for patching is compatible with the waterproofing product.

Waterproofing likes a clean wall. Here’s what I recommend for a surface preparation procedure:

Survey the entire surface to be waterproofed. Identify special problems, such as water on footings, concrete forms not removed, footings not dugout, and pipe penetrations not prepared. Have these problems worked on right away, especially if these areas are the responsibility of another trade?

Dry off all footings. A big propane torch with a 20-pound tank is good for this. For puddles, sweep standing water off with a broom, then dry the damp spot with the torch.

Remove concrete form ties. If there’s an odd form tie that wasn’t aligned properly and won’t break off flush, cut it off with a cutting torch or reciprocating saw. Break form ties off on the inside of the foundation too. Another waterproofer once told me that on one of his jobs, the general contractor sent in a labourer, after waterproofing was applied, to break off form ties on the inside of a foundation. The labourer decided it would be easier to pound the ties back into the wall. Every one of them punched through the waterproofing membrane on the other side, which was already backfilled.

Scrape off excess and loose material from walls and footings. A long-handled ice breaker is good for this. Some waterproofing manufacturers will require you to machine-grind any ridges or protrusions before applying their products. It’s good to have a brick hammer on hand, too. Pay special attention to the footing. Quite often, puddles of congealed slurry form on the footing when the wall is poured. This material doesn’t have the full strength of concrete; it isn’t bonded to the footing and should scrape off easily.

Sweep off the walls and especially the footings. They don’t have to be clean enough to eat off of but don’t leave a film of dust or mud. Waterproofing materials won’t stick to a dirty surface. Keep other trades and workers out of the area. Besides the safety hazards, other workers tend to be oblivious to what waterproofers are trying to accomplish. Many times I’ve cleaned a footing, only to see a muddy-booted labourer stride right down its length, leaving tracks the whole way.

Take care of any patching or filling. Grout around penetrations and follow any other instructions from the waterproofing manufacturer that apply at this point.

At Hitch Property Constructions, we offer Melbourne external waterproofing services. 

The Do’s and Don’ts of Foundation Crack Sealing

Perhaps the most common cause of cracks in a concrete foundation is formed as the concrete cures. This occurs when there is excess water used in the concrete mix, if the concrete dries too quickly, or if the material or location is not properly prepared. While these types of cracks are common, not all of them are alarming and require immediate attention.

Other times, cracks form when the subgrade soil is not properly compacted, or if a material such as trees or roots is buried beneath the foundation. The soil in such cases is vulnerable to sinking, shifting or expanding, which means a lot of pressure is added to the foundation directly, rather than transferred into the earth surrounding the structure. 

And lastly, sometimes water is the culprit. High water tables, or flowing water, can remove or shift soils, and so over time as the soils are displaced, the foundation becomes less stable, and cracks as voids are created underneath the footings.

No matter what has caused the foundation to crack, or whether it is moving or static, the crack should be sealed. Sealing the crack correctly will preserve the integrity of the wall and also prevent water from entering into space within. In this article, we discuss crack sealing from the inside of the wall, as sometimes sealing from the outside is not an option.

During a number of our foundation inspections throughout New Hampshire and Massachusetts, we often come across a crack which had previously been sealed incorrectly, either by the homeowner or by a hired professional. So what does it mean to be sealed incorrectly?

The common mistakes we encounter are surface fills, such as putting caulking into the crack or packing the crack with hydraulic cement. Both of these applications are non-permanent solutions to any crack seal job. While sometimes they may look like a job well done, they are making the problem worse.

These are mistakes for two main reasons. The first being, over time, cement or caulking will either erode or fall away, reopening the crack. The other reason these applications are not effective is that they don’t divert the water away from the wall, but rather end up acting as a dam. With the water being stopped and not allowed to move freely, it can potentially cause further damage to the integrity of the wall, slowly eroding it away.

Don’t let water damage your investment. Sealing and waterproofing chores are fairly easy but can go a long way to protecting your home and keeping it looking sparkling and attractive as well.

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