Renovation & Design
Renovation & Design
Solid base key to avoiding cracked concrete
Question: We are in the process of getting quotes to replace our cracked and heaving concrete driveway. On one quote I was told that the new pour would come up to the garage door concrete grade beam, but would not tie in, to allow the driveway slab to move separately. In the space between they would put corrugated plastic to provide a “buffer” and act as a water sealant. However, on another quote they suggest thickening the new concrete pad in this area and tying the new concrete to the existing grade beam using coated dowels. I can see that keeping them separate allows for movement, but wouldn’t tying the two together possibly cause the grade beam to be affected if they were attached? Which method is preferred in the long term? The quotes are similar in price, but the one that has it tied to the grade beam with the thickened section of concrete is slightly more expensive, but not a deal breaker.
Any advice? I am not sure which way to go.
Thank you for your insight, Scott.
Answer: Connecting a concrete garage floor slab, or grade beam, and the adjacent driveway or approach is not normally a good idea, unless it is done when both are initially poured. Putting small sections of rebar between the two can cause damage to the other component if they move independently of one another, which is likely. Leaving them to move on their own may cause a slight separation or height imbalance, but that is better than cracks or physical damage.
There are many different viewpoints and methods for installation of horizontal surfaces, often from very experienced contractors. Some say that reinforcing concrete slabs for driveways, patios and sidewalks is not necessary, while others insist upon the addition of re-bar or steel mesh to strengthen the concrete. Your question raises a common dilemma, do we try and tie together two adjacent concrete slabs to prevent movement between them? The proponent`s theory is that putting small sections of re-bar, or steel rods, between the two will help prevent an uneven surface, should one heave or settle at a different rate than the other.
The problem with the above scenario, which you have correctly identified, is whether a short piece of embedded steel will successfully accomplish this task, or have other consequences. In my experience, I have seen numerous situations where the “dowels” stay embedded in one of the slabs but come loose from the other.
One reason that pinning two horizontal slabs of concrete together can be problematic is due to the forces that cause them to move, in the first place. Expansion and contraction of the clay soil below these components is normally the culprit. This will occur due to seasonal changes, with the freeze/thaw cycles, primarily due to changes in moisture content in that soil. Because the garage is covering its floor, there is often less variation from normal precipitation. Also, the garage floor may be considerably warmer than the driveway, especially in an attached garage. So, expansion due to frost, snow melting and heavy rains will be more likely to cause the driveway to heave upwards than the garage floor. Conversely, dry summer weather, exacerbated by the hot sun, can cause the soil around and under the driveway to shrink much more than the protected garage.
The last variable to affect these two surfaces differently is vehicle traffic. There can be considerable weight and vibrations from the simple act of driving and parking your vehicles, both on the driveway and the garage floor. If vehicles are mostly left parked for long periods of time on either surface much longer than the other, it may have a settling effect. So, it may be futile to try and minimize this movement by pinning the two large slabs together.
A better approach would be to spend additional time and money on installing a thicker and better compacted granular base for the new driveway. The stability of the new concrete is largely dependent on the substrate below. By removing additional amounts of the clay soil, and replacing it with granular fill, you will be minimizing the effects of soil expansion and contraction. By heavily compacting a thicker stone layer you will create a more stable base, but one that will still drain better than the surrounding soil. Granular fill should not expand and contract like the clay soil, minimizing upwards and downwards movement through the changes in the seasons. So, a better base layer will help prevent movement, not just attempt to hold the two slabs together if they move.
Preventing your new driveway from excessive sinking or heaving, by installing a better granular base, is a much better approach to minimize movement between that and the older garage floor. Small, embedded steel rods, inserted into holes drilled in the garage slab or grade beam, may only weaken the old concrete and potentially cause cracks and damage should either slab move excessively.
Ari Marantz is the owner of Trained Eye Home Inspection Ltd. and a Registered Home Inspector (RHI)(cahpi.ca). Questions can be emailed to the address below. Ari can be reached at 204-291-5358 or check out his website at trainedeye.ca.
trainedeye@iname.com
Renovation & Design
Fresh air intake paramount to comfort of your home
Question: With so many appliances such as clothes dryer, central vac, bathroom fans, and range hood ejecting air from my house, and my high efficiency furnace having intake and exhaust vents separate from ventilated air, what is the solution to preventing unfiltered air from entering the house in an unwanted way? I have negative pressure and get air coming back into the house from my range hood in winter, and need to turn it on full power to get effective air removal from cooking. It seems that’s what HRVs are designed for, but they are expensive and maybe wouldn’t solve the problem.
I don’t have humidity problems, as my bathroom fans do their job. Forums I have looked at don’t take this question seriously, but it seems reasonable to me. Installing a baffled air-intake wherever air is ejected from the house would just let in untreated outside air into that part of house. Can my HVAC system solve this problem in an elegant way or do you have any solution for homeowners for simply providing make-up air due to negative pressure?
Joel Wilke
Answer: Diagnosing and correcting a negative pressure issue within a home can be somewhat complex, but installing a balanced HRV or fresh-air intake duct may be a fairly easy solution. If properly sized and set up, those should equalize the air pressure when appliances and exhaust fans are used.
Because of the air tightness of our newer homes, or older homes that are retro-fit with new windows, doors, insulation and air/vapour barriers, a negative pressure situation can arise. This typically happens, as you have noted, when more air is exhausted from the living area by mechanical systems than can be naturally replenished. This is normally caused by dryers, bathroom exhaust fans, gas water heaters, older furnaces, fireplaces, and kitchen range hoods. When this happens the lower air pressure in the home can cause air to be improperly drawn in through the vents normally used for exhaust. You have noticed this at your kitchen range hood, but is just as common at fireplaces, water heaters, and vent hoods on older furnaces. Those can be much more dangerous because they can allow products of combustion, soot, and other dangerous contaminants to enter the living space. One common problem with negative pressure is that the incoming rush of air can blow out the pilot light on a gas water heater or furnace. That will be the result of back-venting, with those appliances shutting down, which can be a major safety issue, especially in the dead of winter.
The previous serious issue can be mostly resolved by upgrading to a new high efficiency furnace and electric water heater. Because new furnaces vent directly outside and normally have a dedicated fresh air intake pipe, there is no way for back-venting to occur. Those upgrades will make the old chimney/vent redundant, which can be sealed, eliminating one area for air leakage. While that may solve the safety issue in the furnace room, it may only exacerbate the overall pressure issue by further tightening the building enclosure.
The simplest solution to equalize the air pressure when it drops inside the building is to install an insulated fresh-air intake duct. This is most commonly done in the furnace/laundry room if it is located in the basement. It may terminate directly into the room or may be connected to the return air ducting, which will circulate fresh air throughout the house through the HVAC system. This could also be installed with a damper, if needed, to regulate the amount of fresh air drawn inward. The negative aspect of this solution is that it will bring very cold air inside your home in the winter, reducing the overall energy efficiency and raising heating costs.
I am not sure what concern you have with bringing in unfiltered air from outside directly into your home. Unless you live in an area where there are industrial pollutants, or lots of neighbours with wood-burning appliances, there should be little concern. The fresh air from outside will replace indoor air which may contain typical contaminants like carbon dioxide, cooking biproducts, dust, bathroom odours, mould spores, etc. These are normally minimized by natural ventilation and the use of your exhaust fans, but will need clean air to replace that expelled. I am sure that you could install a charcoal filter, or similar filter system, on the fresh air intake duct if desired.
A more modern solution would be to install a Heat Recover Ventilator (HRV) for your home. While a moderate cost to install, it will save some heating dollars every year as compared to a simple fresh-air intake. An HRV should be initially balanced after installation, so that the same amount of air is drawn in as exhausted when it is running. That should all but eliminate any chance of negative pressure issues, but it may not be a perfect solution in your current home. For the HRV to be most effective there should be intake registers in every bathroom, replacing the exhaust fans, and at least one or two other areas in the home. That may require opening up walls and basement ceilings, which will certainly add to the cost of installation. But even a unit connected to the return air ducting, and a few other locations in the home, may be enough to prevent the negative air pressure issues you are experiencing.
Preventing a serious drop in your indoor air pressure when running exhaust fans can be accomplished by bringing in more fresh air to replenish that which is expelled. This should be possible by installing a good fresh air intake duct, or with a properly installed and balanced HRV system.
Ari Marantz is the owner of Trained Eye Home Inspection Ltd. and a Registered Home Inspector (RHI)(cahpi.ca). Questions can be emailed to the address below. Ari can be reached at 204-291-5358 or check out his website at trainedeye.ca.
trainedeye@iname.com
Renovation & Design
There are alternative options to a concrete sidewalk
Question: What are your thoughts on rubber paving blocks or rubber stone, as an alternative to total replacement, for an older concrete sidewalk? William K.
Answer: Replacement of an older settled or damaged concrete sidewalk with alternative materials is a good idea for our soil conditions. To ensure the long-term stability of any paving materials there must be a properly compacted base and curb support.
Concrete is one of the most commonly used building materials, especially for roads, garage pads, sidewalks or other exterior horizontal surfaces. It is extremely durable and able to withstand very heavy loads, vibration, precipitation and other environmental conditions. It also has some environmental benefits such as the ability to recycle some of the components. The main negative property, especially in our area, is the lack of flexibility. Even with the high density and weight of cured concrete, it will have a tendency to heave or settle with changes in environmental conditions. Because of our expansive clay soil in the Red River valley, movement over time is inevitable. This can be prevented, somewhat, by installation of a well compacted base of granular material before pouring.
The initial problem with poured concrete sidewalks may be uneven sinking or lifting with seasonal changes in soil moisture. Frost expansion of wet soil can cause it to lift a long concrete walkway. Alternatively, very dry soil conditions during a hot summer may cause the heavy concrete to settle. If this occurs at different rates along a lengthy sidewalk or pad, cracking will be the first sign of distress. Over time, the cracks may become larger and the horizontal surface uneven. The bigger cracks will let additional moisture penetrate the surface, causing more deterioration to the pavement. Other than physically lifting or jacking portions of the concrete, either manually or with injection through holes in the surface, there may be little choice for repairs. The ultimate remediation is often demolition, removal and replacement.
Using more modern paving materials, such as pre-cast paving stones, blocks, or recycled rubber components, may have a distinct advantage over poured-in place concrete. The benefit of these alternative materials is their relative flexibility compared to rigid slabs. Most of these paving materials are typically installed with very small gaps between components, which is often filled with sand. These gaps will allow subtle movement to occur between individual components, often without noticeable overall changes. They will also allow increased surface drainage, preventing ponding rainwater and melting snow from accumulating. But the biggest benefit may be the possibility of easy removal and replacement of a small portion of the sidewalk, should more significant movement occur.
The above benefits will only be maximized if the substrate below the paved surfaced is well prepared. To allow paving stones or concrete blocks to drain, and prevent frost heaving from saturated clay soil, a good granular base must be first installed below the future walkway. The materials may vary depending on the preference of the contractors, but crushed stone, sand, and other granular fill materials are normally used. The key is to ensure that the base beneath the new sidewalk will not retain moisture from precipitation, lawn watering, eavestrough discharge, or other sources. Also, the granular fill must be well compacted to avoid movement of the paving materials when a load is applied.
The final piece of the sidewalk puzzle will be to properly support the new pavement from lateral movement. This traditionally was done with a narrow concrete curb, installed on the edges of the compacted stone prior to paving. The issues with that method are the same as with a solid concrete slab, as well as the higher cost. Due to the more frequent use of these materials in the last few decades, alternative support systems have been developed. Most of these are very flexible plastic supports, often installed just below grade so they are not visible. They may be installed with various types of metal spikes, re-bar, or treated wood stakes. Once the surrounding vegetation has filled in, these should remain in place for many years without deterioration.
As far as the choice of actual materials for use in your sidewalk, recycled rubber may be one of the most recent available. The benefits include the very green aspect of repurposing discarded tires for the raw materials. Also, the rubber components are almost indestructible and should be easier to transport and installed due to their flexibility. Unfortunately, that flexibility may be a negative property if larger blocks are chosen. These may shift much more easily than their concrete equivalent, which means more frequent leveling and replacement. The upside is that large concrete patio blocks are more prone to cracking, which eventually requires discarding and replacement with new components. For those reasons, using smaller pavers, whether concrete or recycled rubber are chosen, is definitely preferable for less frequent repairs.
Using paving materials derived from recycled tires may be a good choice for a very environmentally friendly new sidewalk, but extra care may be needed in preparing the area before installation. A well compacted granular substrate, with good lateral support, will be required to prevent easy movement, especially due to seasonal environmental changes in our harsh climate.
Ari Marantz is the owner of Trained Eye Home Inspection Ltd. and a Registered Home Inspector (RHI)(cahpi.ca). Questions can be emailed to the address below. Ari can be reached at 204-291-5358 or check out his website at trainedeye.ca.
trainedeye@iname.com
Renovation & Design
Staining pressure-treated decks always a challenge
Question: Our cottage has a large deck on the west side and a small, open porch area on the east side. The deck is made of treated wood and is still solid, but it is about twenty years old and has surface cracks or splinters in many places. A few years ago, we stained both surfaces with a semi-transparent alkyd stain. We had prepped the surfaces with a commercial deck cleaner applied with a stiff-bristled scrub brush, and followed the instructions for rinsing and drying. By the next summer, much of the stain had peeled or faded from the surface of the deck. Meanwhile, the stain adhered much better to the porch area, which was replaced with new wood about ten years ago and is not cracked or splintered.
If we repeat our previous procedure, we will probably get the same result. Is there a better way to prepare the deck so that the wood will hold the stain, for example power sanding and/or power washing? Alternatively, is there a high-quality stain specifically designed for old wood? Or, in your view, is any new attempt doomed to fail in light of the age and condition of the wood on the deck?
Thanks for your response, Gene.
Answer: Staining or finishing the horizontal surface of a deck and expecting it to last may be wishful thinking. Pressure treated wood is designed to last for decades, untouched, so spending money and efforts on cosmetic improvements may be futile, unless you plan to do it every year.
Re-finishing the surface of a deck that is exposed to our harsh climate has always been a challenge. Four decades ago, when I was employed at a couple of local lumber retailers and suppliers, this was a much greater challenge than today. Back then, there were only a couple of options for materials suitable for building an exposed deck. The two most popular were spruce and cedar, with fir being a possible option for the joist structure beneath the decking. Spruce was the most economical choice, but needed to be treated or stained almost immediately after installation to prevent moisture damage and would need to be redone regularly. The quality of the spruce was sufficient for a smooth surface to walk on and strong enough for the beams and joists. Unfortunately, even with regular application of good quality wood stains, the longevity of the material was likely only a decade or so.
A much better option for exterior decks was western red cedar, normally twice as expensive as spruce. Cedar not only was much more attractive, when initially installed, but has a natural resistance to rot. It could be installed, untreated, and often last up to two decades or more. The main downside was that the lovely brown colour would quickly turn to grey, usually within a year, due to the UV rays from the sun. For that reason, various wood stains/preservatives came to the market which enhanced or replaced the cedar look for a longer time. Regardless of the cost or quality of those products, they worked well on vertical surfaces but had a very limited life expectancy, a year or two, on decks and other horizontal wood structures.
During that time, a new product was developed that used preservatives injected under pressure for increasing the longevity of cheaper wood, spruce, pine, and fir. This process would give it a similar or longer life expectancy than cedar, and also help prevent attack by insects. The two main detractions were that the wood surface was impregnated with numerous small incisions, which were use to allow better penetration of the preservatives. The second was that the preservative was copper based, giving the wood an unattractive green colour. The main deterrent, from my viewpoint, was the low quality of the wood used. It was found that spruce would not accept the preservative well, so various species of low-quality pine were used. They were prone to loose knots, warping, bowing, and other negative features. Cedar-like stains were incorporated into the process to mask the green preservative, but would fade over time. Also, the cost of preserving the wood put it more in the price point of cedar, so early adoption was limited.
The good news is that the manufacturers of pressure treated wood refined the process, eliminated the need for incising the surface, and began using better quality pine for their products. For the last two to three decades pressure treated lumber has been the preferred material for not only decks, but fences and other exterior exposed wood products. Unfortunately, even the best quality cedar-coloured preserved wood fades, leaving behind a light greenish-grey tone. Many homeowners, like you, attempt to stain the surface for improved appearance. However, even the best quality products will only last a few seasons before wearing off due to foot traffic, environmental debris, moisture, and exposure to the sun.
Lately there has been a small revolution of products made with various plastics, or hybrids with wood fibre and plastics, which need almost no care and show little deterioration, presumably for decades. While most of these products appear to be excellent quality, they are typically two to three times the cost of treated wood. Pressure treated wood may be used for the structure beneath the composite decking. Also using it for the decking and other components still makes sense, if you can stomach the negative change in appearance, over time.
Pressure treated wood is a good choice for longevity of an exposed deck, but is designed not to need future staining or preserving, which will not last more than a year or two if attempted. Regular cleaning with soap and water, or a pressure washer on a very low setting, may be a better use of your time than perennial staining.
Ari Marantz is the owner of Trained Eye Home Inspection Ltd. and a Registered Home Inspector (RHI)(cahpi.ca). Questions can be emailed to the address below. Ari can be reached at 204-291-5358 or check out his website at trainedeye.ca.
trainedeye@iname.com
