Module 3 Hmk Quiz Q3

[Ben Gorman]

Here is Question 3, along with my thoughts about how to answer it. I don’t know whether or not I have the correct answer. I would be really interested in your comments.

Be aware that the online quiz tends to change the order of the answer options.

**** BACKGROUND TO QUIZ QUESTION ****

Rainwater System
The original cast iron rainwater gutter and downpipes have been replaced with budget UPVC plastic. The original cast iron gutter rafter brackets have been removed when the roof covering was renewed. The plastic guttering brackets have been screwed to the original timber fascia using steel wood screws.

**** QUIZ QUESTION ****

Quiz question 3
A broken downpipe shoe (area g) can lead to:
1. A potential softening of ground under foundations leading to subsidence
2. Rotting of floor joist ends in wall when there is an effective damp proof
course above the break (i)
3. There are no issues as the flower bed is sloping away from house

**** MY THOUGHTS ****

I have excluded 2 because of the mention of DPC above the break. I didn’t think that there could be sufficient rainwater to soften ground because the rainwater would have fallen on that ground area if the building had not been there anyway. However I suppose that the guttering would deliver a large amount of water to a very small area, so maybe it could be a problem.

[Tim Gilbert]

Hi Ben,

I didn’t exclude 2 as the water will come down that pipe with some force and could splash up onto the wall above the DPC. (See also my answer to your shoeless downpipe question).

The building is on shale. Some shales can soften when wet, shale it after all just mud that’s been compressed for the odd million years, but I discounted this answer.

Interesting about the sloping flower bed. It is (or was) a building requirement in Norway that the surface must slope away from buildings in all directions for at least 3m. When you have to level your site with dynamite that’s a lot of extra blasting! (I don’t remember the minimum incline but the maximum was 90 degrees, so no overhangs.) obviously suburbia is not as densely packed as in this country as you need at least 6m between buildings.

Tim

[Ben Gorman]

Hi Tim

Thanks for the info about shale.

If you’re aware of the effect of water softening on shale, why discount it?

Also, I understand your comment about the possibility of water splashing back up the wall. However, I’m thinking in terms of writing a quiz question, the fact that the phrase “DPC above the break” has been used makes me think that the author isn’t expecting any rainwater to splash back above the DPC, so I’m still discounting this option.

Ben

[Tim Gilbert]

Hi Ben,

I have no sound reason for discounting the softening of shale other than that the suburbs of Oslo are still standing.

Yes, I see what you mean about the wording of the question. Try imagining yourself outside this building and examining the wet patch and the down pipe. You might see a distinct delineation where the DPC is or you might not. Either way water might be getting into the underfloor void and increasing humidity to dangerous levels. This could be from splashing or through the porous brickwork below the saturated ground level.

Tim

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