Floors,  Measurements

Measuring floor ‘undulations’!

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Before taking up the floorboards to clear out the subfloor,  inspect the joists and so on, it made sense to measure and document the interesting bowed floor. There is a noticeable hump or hillock in the middle of the room, which is distinctly impractical. Character in a old property is one thing… but this is not really functional for everyday living!

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We used a laser level to ‘skim’ the beam across the floorboards to locate the highest point in the room. This turned out to be the spot right in front of the fireplace hearth. This made some sense visually, since the hearth was angled sharply down from its front edge.

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The lowest point was at the front of the house in the bay window, at around 9cm or 3.5″ below the highest spot.

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The highest ‘edge’ of the room was still 7cm or 2.75″ below the highest spot.

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Another section of the central ‘spine’ wall that supports the upstairs floor joists along with some loading from the roof via struts that support the purlin centres.

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The brick infill stud wall between the lounge and hallway is also just over 7cm or 2.75″ lower than the highest spot. This is interesting because this wall has no loading from upstairs, unlike the other low spots.

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Whilst I had the laser level out, I decided to see how vertical the verticals were! Interestingly, these are remarkably plumb and straight given how wonky the floor is :

Although the house has clearly sunk by several inches over the past 120 years, it has remained very upright regardless.

The phenomena of such a notably bowed or humped floor (as opposed to a sloping floor in one direction) seemed to surprise various tradespeople.

However the phenomena is documented in this fascinating article where it states :

“Victorian foundations were normally excavated by labourers working under the supervision of the bricklayers. Their depth would be nominal and the bottom compacted with a large rammer. Where the ground was not so good, the ramming would be more intensive. Unfortunately the influence of the weight of the building extends beyond that depth which hand ramming can be expected to compact the ground.

It is common to see high initial settlements in Victorian properties, particularly in the gable and party walls, as they are the most heavily loaded. Suspended timber floors are typically supported on an oversite concrete slab, but sometimes on their own foundation. The very limited presence of masonry on these sleeper walls means they settle much less than the external walls. For this reason it is common to see ground floors that are “dished”, ie they have settled around the edges but not at the centre.”

I suspect the majority of houses around here have had this bowing – due to sleeper walls remaining at their original height – leveled out earlier in their life, hence it is something people don’t often see anymore.

Another incredibly informative bit of reading from the University of West England to help understand how these old houses were constructed : “Evolution of Building Elements

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