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Groundwork & Foundations

Level out dip in uneven floor due to uneven and sloping joists

I live in an old Victorian property (at least over 100 years old). The bedroom on first floor at rear of the property measures approx 3.9m by 3.4m. Joists run across the 3.9m length.

I am renovating the bedroom and when I lifted the first floorboard from rear wall to fit insulation I noticed the joists were not level and in particular the middle few joists dipped by about 1 to 2cm. The joists also seem to slope downwards from start of room towards end (the rear of property).

I am not really concerned about the foundation and structure of property. My neighbours had a very similar issue in rear bedroom where he also noticed the dip and when they had a survey done they were told it wasn't anything to worry about. Also we had an extension put into rear of property 5 years ago with its own solid foundations so I am guessing that lends some support to existing wall if anything? Also dips, sags and slopes are to be expected in much older properties.

The joists still seem very solid with no sign of rot or anything. What are my options in levelling out the floor as I want a good levelled floor before I fit the final engineered oak flooring in.

I read sistering joists is one option but seems costly.

Can I pack out the gap between the floorboard and joists with timber and plastic packers to bring it to level?

2 Answers from MyBuilder Groundworkers

Best Answer

packing is one way to solve it but may be a bit hard to get perfect as running on slope . could pack them up were built into walls from underneath to reach same level as other joists will be best option to get perfect. will need to loosen in wall to move up to level and fill in again that's what I would do to get spot on .


Answered 24th Jul 2020

Plant 4x2 joists on to the side of the existing dipping joists, run a string line across all new joists as you install each one, this will give you a level floor.


Answered 24th Jul 2020

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