Old house - undersized joists

[pickles88]

I live in an old house, built around 100 years ago. Ripped up some old laminate flooring downstairs because I wanted to replace it, and thought maybe I could try and make the floor more even below because I want a 240-litre aquarium to go in the corner of the room. Is it a suspended timber floor, sitting about 400mm above the dirt. The room is 7m x 4.5m with a dwarf wall supporting joists half way, so joists are running 3.5m. They are c. 50mm x 100mm which seems very undersized, at 350mm centres.

The stairs are on one side of the room, along with the hallway which is tiled. I can't really get to the joists that run under these. However, I was thinking of sistering the others to strengthen them and maybe use noggins, or maybe even support them from underneath half way along the span with concrete piers or breeze blocks or something. The joists currently go into the brickwork at the front and back of the terraced house. What is best plan? Ideally, I would like the floor stiffer, stronger, flatter and (if possible) more level! What is the best course of action? I am not a novice DIYer but not experience either. I am on a bit of a budget, and whilst I am happy to get a builder in I can't really afford more than 1k for a few months.

Thanks for help everyone.

 

[^woody^]

Whats wrong with the floor?

 

[pickles88]

Whats wrong with the floor?

It's the opposite of flat. Joists have cupped/bowed in places and I'm not sure the floor will take c. 400kg for my aquarium...

 

[Ian H]

You might be better building a solid base for the aquarium off the subfloor.

 

[Footsoldier888]

I am bedevilled by the same issues only mine is springy too. In my case one builder has said it is settlement to the dwarf walls where as another has said it is rot in the joists where they are in the wall. Perhaos they are both right! Just thinking that if you sister and use noggins it might not cure the problem if the joist is rotted at the wall.

Perhaps it would be good to examine the point where it is in the wall. However I do not know how to do this! I have seen that junction upstairs and the joist is mortared into the brick so how do you examine the end? Or is it a judgement thing and they will look a bit ragged or something???

 

[^woody^]

A typical timber floor will have a design loading of about 230kgs /m2, and old 4x2's @ 350 c/c will not be far off a 3500 clear span

 

[pickles88]

Or is it a judgement thing and they will look a bit ragged or something???

I'm not sure. A few of the joists look abit ragged at the bottom, and the wall plate sitting on the dwarf wall doesn't look great. I am going to sister a couple of the joists that have bowed. Do you think it's acceptable to stick a couple of breeze blocks or bricks under the joists mid-span, with a DPM in between the brick and joist?

I also want to increase ventilation. I am going to try and add another air brick. Has anyone added a fan to the subfloor and connected it to the mains ring to run continuously (or on a humidity sensor)?

 

[pickles88]

You might be better building a solid base for the aquarium off the subfloor.

How do I do this? Can I just buy some ready mix concrete, mix it up and pour it into a frame (wood with ply sides lined with DPM)? Do I need to dig out a base in the earth and put some hardcore and sand in?

Thanks

 

[Ian H]

I'd think a concrete base and build it with block. A mate of mine did it for an AGA.

 

[Footsoldier888]

It may be cheap to do that but it's an awful lot of effort unless you can enlist help. There is always the worry of it going wrong too! Wouldn't a wood based solution be easier given you have a decent void space? Perhaps a few I beams say?