Crawl space floor support pillars

[diynob]

Hi all. Living in an omd bungalow and I want to add some pillars under the house (approx 1m of crawling space underneath). My diy mind thinks like this:

Pillars up to approx 0.9m and then joists that run opposite the current joists. I want to do this because the floor is wobbly-ish and I just want to make sure there's extra support in place.

I have a lot of thermalite blocks, 3.6N left over from a previous project so was thinking to make the oillars out of that. I do not want to make a dwarf wall as that would be a real pain, so pillars seem to me to be the right ballance. The floor is finished on top, so it is not possible to take it off and work from above. The thermalite blocks, as the manfacturer claims can be used for foundations as well, so in my mind they would be ok for pillars?

Also, the access to the crawl space is done via 2 hatches in the floor approx 70x50cm, so I would nit be able to fitna full length joist, would have to work with 2m-2.3m joists per length. Pillars would be 2 for each supporting joist, approx 4 per length of house.

Would appreciate suggestions or advice.

Hope this makes sense.

 

[tell80]

Why is "the floor wobbly-ish"?
Without getting into the blocks and pillars i'd just say that using the floor traps to access a long beam or a steel isn't necessary.
You can smash out an air brick &/or remove a few bricks to create a little access hole for sliding the beam through.
Be alert for the DPC and any CWI beads.

 

[diynob]

Sorry, not very specific. When people walk hard the floor essentially wobbles, you can see this on the table in the living room which shakes (metal frame with glass top) and you can feel the wobble in the other room when my son runs around. From underneath the joists do not move, or I can't feel it (I literally stood there with my hand on the joists asking my son to run around to feel the movement).

Longest span of the joist unsupported is aprox 4m. Underfloor is floor boards, 20mm wide, not sure what type of wood they are.

I assumed that adding some support would stiffen the floor a bit.

 

[tell80]

Joist span tables give 38 x 195 sections for approx 4m spans on 400mm centres. Is that the section of your joists?
Finished floor movement without joist movement would only occur in certain (exceptional?) circumstances.

 

[diynob]

Not sure what "38 x 195 sections" means, but the joints are at 35cm to 40cm, they are not equal, BUT some have twisted and that is visible (could explain the different distances between joists. Wobbling is, again, when you jump on the floor or a child runs on it (approx 30kg).

I can't feel the joists moving from underneath, however I suspect there is movement, as there's no other explanation in respect to the wobbling.

Other thing I just thought of is that there is an almost 1cm gap between the wall and laminate flooring, not sure that accounts for anything, but the wobbling is felt in a room with carpet throughout, so maybe not relevant (?).

 

[tell80]

I'm afraid you have no understanding of much of what I'm saying.
Why not google for unfamiliar terms, and pics of floor joists being installed?

 

[diynob]

Took a picture. Joists are 47x175. Distance between them is not consistent, ranging from 35cm to 40cm. There is a wooden dwarf wall which was there.

 

[Tigercubrider]

wouldn't noggins sort this out?

 

[Dereekoo]

wouldn't noggins sort this out?

No

 

[Dereekoo]

Took a picture. Joists are 47x175. Distance between them is not consistent, ranging from 35cm to 40cm. There is a wooden dwarf wall which was there.

Running the calcs and assuming C16 timber at 400c/c (as opposed to C24) your joists are just on the cusp of strength requirements and just over the deflection limits. If C24 is used strength is OK and deflection just on the limit.
Re sorting it I would build piers at 2metreish intervals across the floor in the centre and place suitably sized joists atop to support the existing joists. You could push the new joist tight up against the existing with sliding chocks secured in place

 

[diynob]

So would pillars made out of 3.6N thermalite bricks and a doubled joist across in top be sufficient to support it, possibly stiffen it more?

 

[Dereekoo]

So would pillars made out of 3.6N thermalite bricks and a doubled joist across in top be sufficient to support it, possibly stiffen it more?

That would certainly sort it.