Important tests prior to internal basement renovation works
Which tests must be carried out prior to an internal basement renovation?
What is the accurate investigation method for damage reasons?
The condition of the basement masonry must be examined. In particular, the moisture content and its reasons are necessary. Also the content of water-soluble salts like chlorides, sulphates and nitrates must be investigated at least in a half-quantitative method in order to exclude interactions with the mineral waterproofing.
Type and condition of basement masonry to be waterproofed and its load-bearing capacity as base for the new waterproofing must be verified.
The degree of moisture penetration (ratio between moisture content and maximum water absorption) of the internal masonry walls to be waterproofed must be investigated according to the "DARR" method (exact laboratory procedure for gravimetric moisture determination of building materials) will provide information about the location of a subsequent damp-proof barrier.
Data about room climate like the investigation of temperature of building parts and air ambient, relative humidity rate are requested according to later use of the basement rooms.
What is most important during examination of substrate, when renovating?
The in-stu investigation has a primordial influence on the extent of preliminary works for the provisison of a load-bearing base for the new waterproofing.
For waterproofing works with mineral products non-load bearing layers of render and thin mortar layers as well as paints and floor coverings must be removed. The screed is to be removed in a width of 20 cm from the exterior wall. Renders are to be removed at least 80 cm above the damaged and/or moist areas. The joint network must be scraped out > 20 mm deep. Binding cross walls must be separated in a width of 20 cm from outer walls in order to obtain a uniform transition with other waterproofing levels.
How can the moisture and salt content of basement building parts be determined?
Samples taken in-situ must be representative. They are not allowed lead to wrong results.
The salt load of basement masonry is determined upon the content of water-soluble salts. For this purpose pieces of the masonry surface and/or joint mortar up to a depth of 3 cm can be taken as samples. Alternatively the powder from the drilled holes can be taken for half-representative tests. Through the visual comparison of the colour reation zones of test strips the existence for damaging salts will be proven. The evaluation in low, medium and high salt content will occur in accordance with the WTA leaflet "Damp-proof renders".
Samples can be taken by chiselling out of masonry or via drilled boreholes for the gravimetric method (DARR method). The stone samples must be taken at least at three different heights and at two different depth levels.
The degree of moisture penetration of the masonry is the ratio of the water content by weight to the saturation moisture of the building material. It shows the proportion in % by weight of the pore volume accessible to water at the time of site inspection and sampling with water.