Brick pier foundation

[Bobcat1215]

I have had to dig out my old kitchen floor (about 4m x 3m) which consisted of quarry tiles on top then 1" concrete then about 18" of compressed clinker/ash - a lovely job.

To install a suspended timber floor, I already have a honeycomb wall & plate one end and the other end is the outside wall so I can use joist hangers on that side. Because of the span I will need additional support in the middle, so it's either another honeycomb wall or three brick piers (my preference).

The question then is how deep & wide would I need to go for the pad foundation for the piers?

I am also proposing using 2 courses of engineering bricks on each pier so no DPC will be necessary. Is this OK?

Any advice most welcome. Thanks.

 

[hotrod]

Because of the span I will need additional support in the middle

You quote the kitchen as being 4m*3m - so assuming you're spanning the longest length (4m) what size timbers are you using that mean you are having to provide mid-span support?

I am also proposing using 2 courses of engineering bricks on each pier so no DPC will be necessary. Is this OK?

No harm in running a strip of DPC along the brickwork before you set the timber down. It's pennies and you know it's right then

 

[^woody^]

Instead of an additional wall and foundation, why not just increase the joist depths or fit a purlin?

 

[hotrod]

47mm*200mm C16 @ 400 or 450 centres will span 4m unsupported. If height is an issue use 75mm*150mm C16 (or even C24 if you can source) and fettle the centres right down .

Voila, as Woods has suggested, no need for additional wall or foundation provision .

 

[Bobcat1215]

Woody/Hotrod

Thanks for the advice. I think I'll go with the 75x150 C16 (can't recall ever having seen C24) as height could be an issue.

The existing joists downstairs are all 4x2 and they get away with it by having more piers/dwarf walls than you can't shake a C16 stick at.

What would be the best way of attaching a 75X150 end on to a honeycombed dwarf wall/wall plate built for 4x2's ? Notching out the joist itself would seem to defeat the object...

Thanks

 

[^woody^]

Easiest may be to lay some timber on the wall to a suitable height, and then use hangers

Don't forget noggins or struts at mid-span

 

[hotrod]

The best way of fixing the joists will be dependent on the state of the existing masonry. You could:-

1. "Cut" the joist ends into the existing masonry - remember to wrap DPC round the joist ends / fit boots.
2. Fix masonry joist hangers to the existing wall.
3. Fix a timber bearer to the wall then use timber-to-timber joist hangers.

Using 150mm deep timbers the underside of the new timbers are going to "hang" 50mm lower than the existing 4"*2" timbers so you need to give some forethought to them potentially fouling any DPC / airbricks. It shouldn't be a major issue but something to bear in mind!

Make sure the timber is Vac treated and any ends you cut on site are treated.

hth