Hung Concrete Floors | Explanation
Hung concrete bottoms suitable for domestic construction are generally formed in one of two ways:
1. Using precast concrete shafts and padding blocks
2. Using endless sword formwork or shuttering gauging over shafts or joists with a thin in-situ concrete arbor poured over.
The joists may be of concrete or wood and veritably sometimes of the galvanized cold-rolled sword. The first of these bottoms uses reversed T shafts of prestressed, precast concrete, placed at centers across the needed bottom area. The space between the shafts is filled with blocks. It’s illustrated in Figure2.60.
Generally, the blocks are ordinary structure blocks and particularly featherlight or aac concrete blocks. Some personal systems use especially cast blocks which may be shouldered to fit into the‘T’ ray. They may be especially strong; they may be concave or solid.
Alternatives for the padding blocks are shown in Figure2.61. Blocks can also be made of polystyrene; still relatively strong but giving bettered situations of sequestration to the bottoms. Because the shafts are of prestressed 13,pre-cast concrete.
They can be erected into external walls without the solicitude of ends rotting down, and so save 13 Prestressing is a means of adding the efficacity of the underpinning in a concrete member. Principally, when concrete is poured into a mold the underpinning has been placed in position.
In prestressed concrete that underpinning is slackened before the concrete is poured in. The rebar is of high tensile sword line. The setting concrete grips the line and when the mould is struck the line remains in pressure, literally pulling the concrete together and more suitable to carry high cargo.
on the need for corbelling or conformation of scarcements for joist support They can be cast with a modest depth but in long lengths and so can gauge across utmost houses without the need for slumberer walls.
Spans available generally don’t exceed 8m. However, a dwarf support wall of half slip up thick honeycomb brickwork should be handed, If intermediate support should be needed. The wall must have its own foundation and shouldn’t rest on any oversite concrete layers as the tone- the weight of the bottom is relatively considerable.
A DPC is still needed in the walls, and the shafts should be bedded in mortar incontinently above that DPC. A solum finish is needed, including a DPM. Choose any from those described for bowed timber bottoms. The underfloor void must be voiced in the same way as the void underhung timber bottoms.
Weeps must be handed in the external splint of depression walls. The depression must be filled up to a ground position with weak concrete. Once the shafts and concrete blocks are in place, this rough bottom provides a useful working platform for any work. which is to follow.
This was particularly the case in Scotland where trestles and battens altar was generally erected inside the structure
rather than having an external altar, a situation that has changed vastly since the 1980s.
Once the structure is weathertight, a bottom finish can be applied over the shafts and blocks. A number of options are available, from simple screeds to complex erected layers of sequestration and board or distance flooring. So the ray and padding block bottoms give the structural base upon which a ‘finish’is placed.
The finish can be Timber grounded distance A forfeiture concrete screed. Sequestration may be necessary for the bottom and can be placed below either timber or screed. The timber distance is laid‘ floating’with the distance clear of wall edges to allow for humidity movement.
The wastes are rammed together until the cement in the joints has been set. While it isn’t unsolvable, it’s injudicious to attempt to fasten battens (and nail bottom boarding or distance to them) on this type of bottom.
Generally, the shafts are of veritably thick concrete, making nailing or plugging difficult, while power nailing is apt to shatter the concrete. Nor should one fasten to the blocks as a movement of the timber will displace the blocks and this will affect in a noisy bottom when the inhabitants put their weight on a batten fixed to a loose block. Timber bottoms thus must ‘float’and be allowed to move independently from the concrete base.
The consistency of any screed placed over the sub-floor depends on the purpose to which the bottom will be put and the type of finish placed on the screen. Sequestration may be placed over the bottom under the screed, in which case a minimal consistency of 65 screeds would have to be laid.
In addition, some thin screeds would profit from the addition of light sword underpinning – galvanised funk.
The line would be acceptable to help serious cracking due to temperature and/ or humidity movement 14. A bottom incorporating heating lines or pipes must have a minimal screed consistency of 65.
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