Venting through a support wall

[padstar]

I need to build some support dwarf walls in 2 rooms where the joist are spanning 4m+. I have been told adding a support wall mid span will add considerably to the rigidity of the floor.

The walls will be approximately 3 courses of blocks high. Is it best to leave gaps between each block on the bottom or middle course of say 100mm or to install a few lintels and have far larger gaps of say 1000 (maybe 4 of them over the 10m span)?

What is the best method (even if it is not the cheapest or quickest).

 

[KenGMac]

padstar, good evening.

Suggest you look @

Honeycomb dwarf walls, where gaps are left between each block in all rows, a gap of [say] 100.mm between the blocks will not impede air flow too much.

Install concrete pre-stressed lintels with the lintels spanning between block work or brickwork piers. Each end of the lintel can be resting on a pocket + pad stone cut into the existing walls.

Ken.

 

[padstar]

Thanks Ken. Is 1 method prefered over the other or do they both give the same results?

 

[KenGMac]

padstar, good evening, again.

The first method, could be considered more "traditional"

As for which method?? it comes down to preference and logistics, such as.
1/. In method 1 a full width foundation will be needed to support the blocks. [sub plot --- removal of excavated material?? and additional Concrete for the founds?]
2/. In method 1 an access space may be needed to get from one area to another, this will probably need a small lintel?
3/. In method 2 a smaller area of foundation is required.
4/. In method 2 you need to ensure that the lintels can be manhandled into the access to the underfloor, which in turn may??? dictate the center to center dimensions of the piers + the number of piers??

Consider? use treated timber only for the "wall plate" under the joists.
Fit a DPM under the treated timber.
Leave a [say] 10 / 15. mm. gap between the [so called] wall plate and the floor joists. makes actually getting the wall plate into place, then use treated timber packing between Wall Plate and underside of individual joists. [Joists are at times notorious for differing depths??

Ken

 

[padstar]

Thanks. I think I will go with blockwork with lintels to give larger spans of free space and air circulation. All old joists have been removed so it is a fresh canvas and getting lintels etc in there will be no problem. Thanks again

 

[padstar]

Over a 9.5m support wall would 4nr 500mm openings be sufficient for venting the floor void?