How to build a pier foundation raft - instruction

Selecting any type of substrate structure is determined by local conditions.To say that this structure is the most common, it is impossible.Pier foundation raft with popularity lags behind the most commonly equip tape, but sometimes it is more expedient to build after all it was his.

Palm primacy in the invention of the "mixed" design experts give the Finns.And it is called mixed because a pile foundation has a belt and elements of the base.It has its own dignity, which cause specificity of application.Suffice it to say that the cost of its construction is about 4 times lower compared to the monolith.By the way, there are other names for this design - columnar-tape and columnar-rostverkovaya.

Features

• relatively low cost, since the material consumption is small.
• possibility of their choice.This base is mounted not only from concrete.Erecting poles and brick, stone, in some cases - even wood (eg larch, cedar, oak).
• Lack basement.Therefore pier foundation is more suitable for industrial, warehouse and commercial buildings (eg barns, baths).Under dwellings settling it, if another type of base is not appropriate.For example, water subterranean formations are located close to the ground.It is clear that in this case, to mount the tape base does not make sense.Although small cottages such a foundation - a great option for any ground.
• Ease of construction and low labor intensity.
• convenience of construction.You do not have to dig a trench (for slab) or a large trench (a monolithic tape or team).
• columnar-rostverkovy foundation, unlike tape or slab can be constructed on difficult terrain, even on slopes.

consider the most durable option - on reinforced concrete pillars.But first is to clarify that a grillage.

data bases, depending on the location of the poles relative to each other, and are subdivided into single spray, and their installation - by hanging, and "rack", buried or unburied.They, like the belt, are monolithic or teams.It depends on the future operating conditions that defines how devices grillage.

Consider one embodiment of the construction in general, as determined by local conditions nuances, therefore, certain structural features such bases will be selected for each structure.

Before installation, it is necessary to hold a series of preparatory measures, first and foremost, to make calculations.But this is a separate big topic, so let's get right to the production of works.And look at the most simple method of installation.

technology

Site preparation work

Along the perimeter of the future structure of the layout is done (read about it here), and then remove the top layer of soil ( "tape").After that, in places, defined the project for the installation of poles, digging pits.The depth should be greater than the level of soil freezing in the area, plus a 25 - 30 cm in order to then make the filling (the so-called "pillow").

determine the size of the pits, we must note that the calculated dimensions of the post will be mounted in the formwork and its walls also have their size (thickness of the board, 1 on each side of the square).In addition, support frame and yet to be set in place, after which reinforce spacers.

last event at this stage - waterproofing bottom.This should be done for 2 reasons.Firstly, during the casting solution will leave the moisture in the ground, that may disturb the natural curing process and to reduce the structural strength.Secondly, the packed material during operation of the structure will act as the isolation compartment, preventing penetration of moisture from the ground into the concrete columns.

typically used roofing material, but its life is not more than 4 - 5 years.Therefore it is better to work with polyethylene or something similar.

Decking

As a rule, it is made removable.The cheapest option - use doski- "twenty".Of these knock box and placed in the pit.Then - struts.

Sometimes formwork and is not done, if the land is in the pit dry, hard, and she dug just below the column size.Suffice it to her sides and bottom to put waterproof material and can be filled with a solution.

Formwork is removed the day after 4 - 5, when concrete "grab".

Reinforcement

It is necessary to reinforce the concrete.Such frames are gathered outside the well and then dipped into it.Since they are collected from a metal rod, it must be protected from corrosion.To prevent direct contact with the liquid, the amount of reinforcing structure is selected in such a way that after the pouring of concrete and a layer between the shuttering walls (pit) and bars was at least 5 cm on each side.Even then somewhere pillar partially crumble, the rods are not "Expose".

Their connection is made only to "viscous".Welding leads to overheating of the metal that the "dot" alters its structure and reduces the strength in these places.

should be remembered that the vertical bars must be above the fill level, as they will be connected to the raft.

Fill

solution feature is that it should be done "a la carte".Each layer must be carefully compacted.To do this, use the same rod, bayonet spade, if possible - the vibrator.The task - to remove all the air is caught in a solution which forms a cavity which reduces the strength of the post.More fill examined in detail here.

There is a nuance.It is impossible to fill the formwork in parts.For example, a half day, and the rest - the next day.The fact that the night partially loaded concrete "grab", and a seam is formed between the casting and the second half.On the strength of the structure of the monolith in this case, can not speak.

External machining pillars

After removing the formwork the upper sections of concrete structures are protected waterproofing layer (gidrostekloizol, bitumen and the like), thermal insulation, then backfilled pit.If the soil from heaving discharge, it is best not to use the land, and take, for example, the sand coarse fractions.

Installation grillage

He is or on the ground, or above it.Supporters of the second variant claim that this method excludes any impact of soil (and water) in the grillage.

Further, all as in the construction of strip foundation: formwork between the posts - "pillow" - waterproofing - reinforcing cage - pouring concrete.

grillage to raise, you need to increase the thickness of the sand filling (although there are other options).And if it is mounted on the ground, it is necessary to dig a shallow trench, to the upper edge of the "cushion" was on the ground level.Nothing complicated.

All activities are identical to the above - seal pillows and a solution size of the reinforcing assembly.After the "seizure" of concrete when "hanging" grillage "cushion" is removed.

Do not forget that the reinforcement frame must be securely connected to the left of each mounting post ends of the vertical bars.

Some rules

• pillars (support) on a mandatory basis are set in all the "nodal" points (the intersection or junction of walls, corners of buildings).
• optimal distance from pillar to post -. 2.5 to 3.5 m Its increase may lead to destruction of the raft foundation, and a decrease in consumption of building materials will increase (and labor).

Practical advice

• Such foundations are well-suited for areas with irregularities that are "smooth" it is not possible or inadvisable to do it for some reasons.They are developing are in areas with a large depth of freezing or high groundwater.
• prefabricated build a lot easier, and the time required is much less.But if you expect a big load, then mounted the foundation monolith.If
• build permanent shuttering of the slabs Penoplex, such a structure will increase the service life of poles.The material is simultaneously protects against frost and moisture, and the loads due to the systematic soil movements.
• shuttering Option for "hanging" grillage next.Along the perimeter of the bricks are laid, which is set formwork, but with the bottom (of the board).Then it is easy to dismantle.
• nailed together before putting the casing in place (in the pit), it should be well moistened with water.Firstly, it then comes off easily, as it does not stick to the concrete.Second, the board will not be out of it "pull" water.