Going slow – like many months for a simple investigation, longer still for complex ones, ensures the cause of the problem is determined.\u00a0 And the investigator doesn’t succumb to the tyranny of the obvious – as\u00a0I almost did. (Ref. 1)\u00a0 You’ve got to have time to think and reflect.\u00a0\u00a0Going slow\u00a0also helps the owner adjust to seeing his property taken apart during the work.<\/p>\n
I investigated the cause of two wet basements in the past 1.5 years. \u00a0More than just wet, a flood in one case, 3 inches deep, and very wet in the other.<\/p>\n
There was also water in\u00a0depressions on the properties\u00a0that sloped down to nearby lakes.\u00a0\u00a0That meant\u00a0poor surface drainage and probably high water tables – evidence of a possible cause of the wet basements..<\/p>\n
The homeowners<\/strong> helped in both cases.\u00a0 One\u00a0used a novel\u00a0method for determining the correct cause of\u00a0her wet basement<\/strong>.\u00a0 I’ll use her simple technique in future.\u00a0 The other was in the right place at the right time to see the actual cause of their wet basement, and in a very striking way.<\/strong><\/p>\n Both Houses<\/strong><\/p>\n Both basements were finished including the floors.\u00a0 But you could see water flowing from under the finished floors and across the exposed concrete floor in adjacent furnace rooms.\u00a0 The water came from the direction of the basement walls on the up-slope side of the properties.<\/p>\n We\u00a0cut small holes\u00a0in the gyproc\u00a0at the bottom of the\u00a0walls and gradually added other holes\u00a0and enlarged them – in a sense, we<\/strong> chased\u00a0the wet basement problem<\/strong>.\u00a0 This exposed the wood sill at the bottom of the walls and the area where the concrete floor abuts the concrete wall.\u00a0 We also took up part of the finished floor in one house.<\/p>\n The owners helped and we went slowly so they could get their heads around the dismantling and the mess.\u00a0 These were well-appointed, $350,000 plus homes, one about 30 years old and the other 40.<\/p>\n The exposed wood sills were water stained at both properties.\u00a0 The stain gradually faded along the length of the wood sills from a dark area in the middle.\u00a0 The stain indicated the wall was leaking, and the\u00a0dark area\u00a0suggested the location of the leak.<\/p>\n Just to be sure<\/strong>, we cut small holes in another wall in each house well away from where the water was seen in the houses.\u00a0 We saw clean, unstained wood sill indicating no leaks.\u00a0\u00a0There was a leak along one of these adjacent walls 20 years earlier that was fixed by\u00a0constructing a new, perimeter footing drain.\u00a0\u00a0Fine soil clogs these\u00a0drains often enough after a few decades.<\/p>\n I concluded a clogged footing drain was the cause of the flooding at both houses,<\/strong>\u00a0a good initial hypothesis as to cause.\u00a0 But, I was in for a surprise.<\/strong><\/p>\n (You can imagine there was quite a mess in both houses now with dismantled wall debris everywhere.\u00a0 But we were going slowly – weeks now, and soon months)<\/p>\n Where was the leak?<\/strong>\u00a0 How was water getting from a clogged footing drain into the basement – if that was the source?\u00a0 The concrete wall was stained a little at the location of a hairline crack in one house.\u00a0 But this crack was so fine I quickly dismissed it as the source of the leak, and it was above the suspect footing drain.\u00a0 Surely such a tiny crack was not the cause.\u00a0 Surely.<\/strong><\/p>\n Where was the leak then?\u00a0<\/strong> I thought about the construction joint where the concrete floor abuts the concrete basement wall in both houses.\u00a0 It measured 1 to 1.5 mm wide and\u00a0ran the length of the walls.\u00a0\u00a0The construction joint\u00a0was also down near the suspect footing drains on the outside of the basement wall.<\/p>\n I concluded<\/strong> that the footing drain at both homes was clogged after 30 and 40 years, water was backing up in the drains and getting into the basement through the construction joints.\u00a0 We would dig up the footing drains at both houses and fix them.<\/p>\n It took me a while to\u00a0conclude that construction joints could admit so much water.\u00a0 The penny dropped, so I thought, when I realized that\u00a0not much water would flow through\u00a0a 1.5 mm hole\u00a0but a lot would flow through\u00a0100s of 1.5 mm holes joined together.\u00a0 Like a line of holes in a sieve or the holes in a garden hose used for irrigation.<\/p>\n House #1<\/strong><\/p>\n But, again, just to be sure<\/strong>, we uncovered a greater height of wall in House #1<\/strong> – more time more debris, and saw that an area of the wall was honeycombed a few feet above the wood sill.\u00a0 There were small holes in the wall between the pieces of gravel in the concrete.\u00a0 The inside wall was porous.\u00a0 This happens when the concrete is not\u00a0well mixed during construction.\u00a0 It doesn’t usually cause\u00a0a problem because it’s localized and above the footing drain.<\/p>\n Fortunately, we had a very heavy rain a few hours after work.\u00a0 My client called to say water was flowing from the honeycombed area like water from a tap.\u00a0 It\u00a0stopped shortly after the rain stopped.\u00a0 He videotaped and I saw that it was so.\u00a0 My client was in the right place at the right time.<\/strong><\/p>\n We uncovered more wall later and found that a large area was honeycombed.\u00a0 We also uncovered the outside of the wall and saw that the honeycombing – the porous area, continued\u00a0through the wall.\u00a0 We also\u00a0saw that the water table was at the level of the honeycombing.<\/p>\n There was a source of water and a means for the water to get through the wall, through the porous honeycombing.\u00a0 The honeycombing\u00a0and the high water table were\u00a0the cause of the wet basement in this house, not the footing drain.<\/strong><\/p>\n We fixed the leak by patching the outside of the wall well above the footing drain that we had considered digging up, and at much lower cost.<\/p>\n (The patching details are not\u00a0so important to my message here about the advantages of a “slow”, thorough engineering investigation)<\/p>\n House #2<\/strong><\/p>\n Also, again to be sure,<\/strong> my other client, House #2, decided to investigate the innocent-looking, fine crack<\/strong> in their wall when I was away.\u00a0 She simply took a garden hose and let it run for some time at different locations against the wall starting at the fine crack.<\/p>\n She saw that water flowed through the crack and stopped when she\u00a0removed the hose.\u00a0 She also saw that less water flowed when the hose was at\u00a0increasing distances from the fine crack.\u00a0 The fine crack and a water filled depression in the sloping ground were\u00a0the cause of the wet basement, not the footing drain.\u00a0<\/strong><\/p>\n We fixed it too by patching the outside of the wall at the location of the crack, also at a much lower cost than digging up the footing drain.\u00a0 We did expose the top of the footing drain over a short distance during the patching.\u00a0 It appeared to be well constructed.<\/p>\n (We are going to monitor the effectiveness of this repair over the next couple of years)<\/p>\n ***<\/strong><\/p>\n So, four or five months later in both cases after a “slow”, thorough\u00a0investigation – and\u00a0a lot of gradually accepted\u00a0mess, we determined the correct cause of the wet basements.\u00a0 And we fixed them for a lower cost than might have been the case if I\u00a0had\u00a0remained in the grip\u00a0of the obvious.<\/p>\n References<\/strong><\/p>\n <\/p>\n <\/p>\n","protected":false},"excerpt":{"rendered":" Going slow – like many months for a simple investigation, longer still for complex ones, ensures the cause of the problem is determined.\u00a0 And the investigator doesn’t succumb to the tyranny of the obvious – as\u00a0I almost did. (Ref. 1)\u00a0 … Continue reading \n