GB2139687A - DPC installation - Google Patents

Abstract

A DPC is provided by removing an envelope mortar along a length of a course, disposing in the resulting space, and charging the envelope with uncured mortar under sufficient pressure to expand the envelope into close contact with the local structural surfaces between the longitudinal extremities of the evacuated course. Instead of removing mortar, a fissure may be cut in a structure. The envelope may contain a dry mortar mix, or a filler, e.g. sand, to which uncured resin may be added. The envelope may be pleated. It may be held in place by a spring. The upper layer of the envelope may allow air to escape. <IMAGE>

Description

SPECIFICATION DPC Installation The invention relates to a method of inserting a physical damproof course into any type of brickwork, stonework or blockwork suffering from rising damp.

Rising damp caused by capillary action and even rising damp caused by water pressure in basement partition walls causes enormous damage in terms of breaking down of plaster and blistering of paintwork. If water is allowed to continue to rise and evaporate from the plaster, dissolved salts will be carried up and cause a build-up of salts in the plaster. These salts will break down the plaster and re plastering will be necessary. There are well known methods of controlling rising damp by drilling holes into the wall at regular intervals and injecting crystal-forming penetrating chemicals or water repellants such as silicones or stearates.

It is also commonly known to cut out the joints in small sections and insert a physical DPC in the form of lead sheet, bituminous felt or plastics sheet and then repoint the joint with a strong mortar, leaving an end gap to facilitate lap jointing. The difficulty with this method is that it isvery difficult to ensure that the repointing is well compacted, homogeneous and coextensive with wall depth so as to prevent any settlement of the building. It is particularly difficult to ensure a satisfactory repointing in the case of cavity walls where access to the rear of the wail outer skin to prevent the mortar dropping out into the cavity is impractical. The invention provides methods of inserting a physical DPC into any type wall, section by section, or continuously, and a method to replace the repointing process with a simple, better and much more reliable method.One method comprises cutting out the joint (e.g. in the normal manner in approximately 2 foot lengths leaving approximately 2 foot to carry the load of the wall and then cutting out a further 2 foot length) inserting a plastics bag with at least one (eg, two or more) valves, for example non-return valves, pumping the bag full with a cement grout, a cement/sand or a cement sand grout containing waterproofing material and/or a rapid hardening additive or a cement sand grout containing an additive as above-mentioned or of any other kind (the simplest form being aluminium powder or an aluminium salt or an expanding cement); a resin grout (e.g. epoxide or similar) can be used. The bag should be made of flexible soft plastics material (e.g. a rubber material) examples being polyethylene, PVC, Ethylene copolymer etc (ail flexible materials).

The bag can be made of the same thickness materials or with a stronger or thicker bottom layer. Said bag should be made in the same thickness (width) as the wall depth or slightly less or slightly more, and a length suitable for the cut plus an allowance for a pleated-up section at each and to provde overlap for lap jointing and, in case of waterpressure, for being jointed and sealed to the adjacent bag by heat or solvent welding or frequency welding.

The bag should be flexible enough that when pumped full with cementitious grout or a resin grout, whether expanding or not, it completely fills all cavities between the courses of brick or stone or blockwork and is also able to fill out and support the brick when bricks have been laid with their frogs facing downwardly (see Sketch No. 1). Said bag would normally be made of fairly thin 0.1-0.5 mm soft plasticised PVC material so that material can be pleated together so that it is easy to insert into the joint. When the bag is pumped full the bag will expand to completely fill the joint.

According to one aspect of the invention, a DPC is provided in a building structure composed of coursed building elements separated by courses of mortar by removing said mortar along a length of such a course, disposing in the resulting space an envelope and charging to said envelope an uncured mortar under sufficient pressure to expand said envelope into close contact with the local structural surfaces between the longitudinal extremities of the evacuated course. The term "mortar" used above includes any bonding material suitable for use in building structures of the kind referred to and includes in particular cementitious materials such as cement grout and sand/cement mortar, as well as resin grouts (e.g. epoxy based grouts, e.g an epoxy resin filled with, for example, a cementitious filler).A "mortar" of two or more components may be provided as separate charges of components or by charging one component to an envelope containing one or more others when placed (for example, the envelope may be disposed when already containing, for example, a sand, and a resin charged to the envelope in situ). The DPC is normally provided by the material of the envelope which may be of such water-impermeable material as a plastics material (e.g. low or high density polyethylene, ethylene copolymer, polypropylene, ethylene copolymer, polypropylene or PVC), but may alternatively be provided by inclusion of a silicone or other impermeabilityimparting agent in the mortar or by providing separate DPC membrane material (e.g. as referred to earlier) in the space vacated by the removed cured mortar.Two or more of such methods of providing the DPC may be combined (e.g. a plastics material envelope charged with water-proof grout).

This method need not be carried out by highly skilled people and is even suitable for do-it-yourself people.

The second method requires more specialist skill and experience; it allows continuous cutting and installing of the DPC and at the same time provides the support and repointing.

This method comprises of placing behind the cutting wheel or saw a pleated bag of any soft flexible material as mentioned in method 1 above, in widths of slightly less or more than the thickness of the wall when pleated.

In a 10mm high horizontal joint with a bag thickness of 2 X 0.25 (= 0.5) mm, a 2 metre long bag can be pleated up so as to occupy only 100 mm in length. The bag is held in place by two springs attached to a metal blade or scraper foliowing the cutting blade, and as the cutting blade advances the bag is released one pleat at a time. A grout is constantly being pumped into the bag from the other end at a closely controlled pressure so that the pressure in the bag is exactly able to carry the weight of the wall without the wall moving up or down (possibly a pressure of > 5 atmospheres gauge).

To eliminate air bubbles in the bag, the upper layer can be of a type of material that allows air to escape without allowing the grout to escape. The grout can be made of any cementitious or resin grout that sets hard, or even be replaced by an air-tight bag where fine sand is blown in and compacted, and later solidified by a resin being pumped in.

In a particular embodiment-of the invention, the mortar course is removed continuously over a length which may equal the course length by a blade urged continuously to cut through the mortar across the width of the course and to remove mortar debris from the resulting space, an envelope (e.g. of plastics material) comprising a plurality of sections folded in section-to-section fashion, for example with a first unfolded length, being inserted into a space vacated by mortar whilst mortar course removal is incomplete, fluid mortar being pumped to the cavity of said envelope under pressure such that folded sections thereof successively fill with mortar and are urged into contact with local structural surfaces as described earlier and so that filled envelope extends along the length of cut of the blade behind its trailing edge. The mortar will normally be rapid hardening when loadbearing considerations so require although pumping pressure may be so selected as to bear the structural load during curing.

This invention includes within its scope a valved envelope as just described and further includes a folded or unfolded envelope containing a dry mix mortar material, or filler (e.g. sand) to which uncured resin can later be added. The invention also includes any of the methods described earlier when applied to structures having no mortar courses, the DPC being inserted between faces of the structure opposing each other along a cut or similar fissure formed in the fabric of the structure.

Claims (11)

1. A method of providing a DPC in a building structure composed of coursed building elements separated by courses of mortar by removing said mortar along a length of such a course, disposing in the resulting space an envelope and charging to said envelope an uncured mortar under sufficient pressure to expand said envelope into close contact with the local structural surfaces between the longitudinal extremities of the evacuated course.

2. A method as claimed in Claim 1 wherein the uncured mortar is a plastic composition comprising a cementitious material or a resin grout.

3. A method as claimed in Claim 1 or Claim 2 wherein the uncured mortar contains a water impermeability-imparting agent so that on curing as a mortar course said course acts as a DPC.

4. A method as claimed in any one of Claims 1 to 3 wherein the envelope is made of a water-impermeable sheet material.

5. A method as claimed in Claim 4 wherein the sheet material is polyethylene, ethylene copolymer, polypropylene or polyvinyl chloride.

6. A method as claimed in any preceding claim wherein the envelope has a cavity defined between an upper envelope portion perforated to allow gas to escape upwardly therethrough after charging of mortar to the cavity and a lower envelope portion.

7. A method of providing a DPC in a building structure composed of coursed building elements separated by course of mortar wherein a mortar course is removed continuously over a length which may equal the course length or be less than the course length by a blade or other cutting means urged continuously to cut through the mortar across the course width and to remove debris from the resulting space, an envelope comprising a plurality of sections folded in sectionto-section fashion and extensible by unfolding in response to pressure applied in the cavity of the envelope being inserted into a space vacated by mortar, and fluid uncured mortar being pumped to the envelope cavity under pressure such that folded sections of the envelope successively fill with mortar and unfold so that the filled envelope extends along the length of the cut section-by-section, the envelope being urged into contact with local structural surfaces between the longitudinal extremities of the evacuated course.

8. A method of providing a DPC in a building structure substantially as hereinbefore described with reference to the accompanying drawings.

9. A method of providing a DPC in a building structure composed of coursed building elements separated by mortar courses which method comprises progressively disintegrating a tract of mortar coursing and removing mortar debris to leave a space defined between opposed structural surfaces previously joined by said mortar, disposing in a portion of said space an envelope which defines a variable-volume cavity between envelope wall members which are extensible in response to pressure applied in said cavity so that the envelope extends with increasing volume along the space vacated by the mortar on application of such pressure, charging to said envelope a curable plastic load-bearing filler material under pressure so that the envelope expands and extends along said space with its walls closely urged into contact with said structural surfaces by said filler material and allowing said filler material to cure so that said envelope as filled with cured filler material which acts as a load-bearing DPC in the building structure.

10. A method as claimed in Claim 9 wherein a mortar-removal means includes a member which penetrates said mortar course and is advanced between said opposed structural surfaces along the tract, said envelope once disposed in said space being supplied with pressurized filler material so that the envelope advances along said space as said member advances.

11. A method as claimed in Claim 10 wherein the envelope comprises two opposed pleated wall members defining said cavity there between and each preferably juxtaposed with a respective one of said opposed wall members.

1 2. A method as claimed in any one of Claims 9 to 11 wherein the envelope extends lengthwise against the bias of spring means connected with said envelope.