Block Basements: Part Five

The Dig Begins

Last week we listed off the procedures that are needed to properly prepare a site for excavation around a block basement, in previous weeks we discussed waterproofing methods and reasons why block basements are known for water issues. There are several advantages to digging up a basement and certainly benefits from insulating the exterior of the foundation. Some of the companies that manufacture waterproofing coatings and membranes require an insulation barrier applied to the wall after covering is installed. This is done to protect the waterproof barrier from damage by soil or rocks when the back fill work is done. While it is not required, unless it’s a manufacturer’s standard, exterior insulation applied to the foundation is not as common as it should be. There is the cost factor here and often the five-figure excavation “hit” on the family budget is enough that the additional two or three thousand for rigid foam insulation is beyond available funds. Installing rigid foam insulation will dramatically reduce the level of condensation in the block walls. It might mean a vapour barrier on the interior wall may not be needed. It protects the walls from additional air leakage provided this insulation application is installed up the wall fully including the rim joist or header areas, whichever term you like. This insulation will dramatically improve the air quality and temperature in the basement.

A couple of years ago I was on a major renovation and basement excavation site and the owner was hesitating on the cost of the insulation. I took him inside and we took the temperature of the home’s main level by using a laser thermometer. We then went to the unfinished basement and there was a seven-degree difference. I told him that properly installing the external rigid foam and including the rim joists would close this gap by around 50%. He bet me a steak dinner I was going to be wrong….I enjoyed the dinner….his basement was 2 degree different from the main level when the job was done.

 Now on to the dig and everything was getting ready. The chosen contractor was carefully going thru their Excavation Assessment sheet as their crew unloaded the track hoe. I was pleased to see the size of the equipment on site. Some years ago, I had a block wall fail because we allowed a full sized back hoe too close to the block wall. They had put up the stakes for the safety fence and the operator slowly began at the edge of the foundation removing the soil and piling it away from what became the hole beside the foundation. Large rocks and any hard clay pieces were separated and removed from the stored soil. The contractor said they will use the existing soil provided it is suitable, if not they replace it with better draining soil. If present, they also removed the old clay drainage tile. Some homes built before the 80’s when “Big O” came into popularity had a clay tile drain system installed around the foundation. The contractor stated that nearly 100% of those that they dig up are filled with silt and roots, long since failed in their usefulness. All of this waste is removed from the site.  

Once the trench is dug they carefully shore up the walls with braces and plywood to protect their staff, they were adamant at this point about the crew’s safety in the trench and watched over this installation carefully. They now began the arduous task of scraping down the walls and checking for any major cracks or openings in the foundation. Depending upon the severity of the cracks they use professional crack sealants or a prep coat and a mesh type covering that is imbedded into the prep coat. The contractor said each job is different and they come prepared for different crack and patch work. Next step is the time-consuming work of preparing the walls by scrapping them down, pressure washing if necessary and removing any old parge that is still present that would be below grade. At this point they try and establish where the drain tile will discharge. The contractor said this can be frustrating at times as many homes never had a proper discharge to the storm sewers or a dry well.

Once everything is prepared and the trench cleaned out, the clear stone is brought in. A layer is set at the edge of the foundation to “bed down” the perforated plastic pipe that will become the drain tile. The contractor said this is one of the most important areas, ensuring that it sits beside the footings and has a proper base for drainage.  This trade has a policy of adding close to three feet of gravel from the base up the wall. They recognize this may be “over kill” but they feel the extra cost is outweighed by the benefits of proper drainage.

Next, we look at the backfilling of the site, final grade work and discuss the different kinds of sump pump installations. We will look at both internal and external pump installations.    

Leave a Reply

Have Any Questions?

Do not hesitate to contact us. We’re a team of experts ready to talk to you.

© 2024 CAC Group | Cam Allen Consulting | All Rights Reserved

Created by Web Dezyn Plus

Leave a Reply