Ways of deal­ing with damp pen­e­trat­ing ren­dered walls

Yorkshire Post - Property - - PROPERTY - Jonathon Wing­field

We live in a de­tached house that is ren­dered but is now show­ing signs of hair­line crack­ing. Over the last few months we have also no­ticed that damp patches in some of the rooms, lead­ing us to think that the ren­der is fail­ing. We have seen ad­ver­tise­ments for pro­tec­tive coat­ings and some of our neigh­bours have had these ap­plied to their houses. They come with a 20-year guar­an­tee so we are very tempted, par­tic­u­larly as we have had a quo­ta­tion and they ap­pear to pro­vide an ex­tremely cost ef­fec­tive so­lu­tion. Have you any knowl­edge of their ef­fec­tive­ness?

Un­for­tu­nately I have no first­hand knowl­edge of these sys­tems. How­ever, if the deal looks too good to be true then it prob­a­bly is. Es­sen­tially there are no quick fixes with build­ings. Fur­ther­more, any guar­an­tee is only as good as the com­pany giv­ing it. Many are run on a fran­chise ba­sis so whether they will still be trad­ing in 20 years is de­bat­able. The guar­an­tee there­fore has limited value.

With re­gard to their ef­fec­tive­ness I have no doubt that un­der lab­o­ra­tory con­di­tions they can prove their prod­ucts are wa­ter­tight. Ap­ply­ing the same coat­ing to a va­ri­ety of sub­strates such as brick or con­crete that are then ex­posed to the el­e­ments is a very dif­fer­ent mat­ter and I am not con­vinced it will pro­vide a good long-term in­vest­ment.

The fact that your walls are damp does sug­gest the ren­der is fail­ing and mois­ture is be­ing trans­mit­ted across a solid wall, most likely con­structed from soft brick. The ce­men­ta­tious ren­der­ing is pre­vent­ing the walls from breath­ing so that mois­ture is ei­ther be­ing trans­mit­ted through to the in­side or is ac­cu­mu­lat­ing un­der the ren­der and there­fore caus­ing cracks to ap­pear. Cov­er­ing the ren­der with a wa­ter­proof­ing sys­tem will ul­ti­mately only make the sit­u­a­tion worse. Ide­ally, the old ren­der needs hack­ing off and re­plac­ing with a lime ren­der that can be dec­o­rated us­ing a lime wash. This will al­low the wall to breathe and func­tion as orig­i­nally in­tended.

We would like to ex­tend our house but the de­vel­op­ment con­trol of­fi­cer has con­firmed that we need a ground in­ves­ti­ga­tion re­port to ac­com­pany the plan­ning ap­pli­ca­tion. This is de­spite the fact that we have a copy of the orig­i­nal con­sent for the es­tate when it was ap­proved back in the late 1980’s. How can we avoid ex­pen­sive ground in­ves­ti­ga­tion work?

With any plan­ning ap­pli­ca­tion it is the re­spon­si­bil­ity of the ap­pli­cant to pro­vide the nec­es­sary in­for­ma­tion needed to al­low an in­formed decision to be made.

The Lo­cal Au­thor­ity and NHBC may have some in­for­ma­tion on file from the orig­i­nal ap­pli­ca­tion and even be pre­pared to share it with you but they are not un­der any obli­ga­tion to do so. Ex­tend­ing houses can of­ten lead to is­sues with foun­da­tions, par­tic­u­larly when build­ing on clay or in ar­eas with a his­tory of un­sta­ble ground. Dif­fer­en­tial set­tle­ment through shrink­age from ei­ther the in­creased load­ing and or changes to ground-water con­tent can take place with cracks ap­pear­ing where the old meets the new. Although not en­tirely suc­cess­ful the in­tro­duc­tion of an ex­pan­sion joint along the en­tire junc­tion can mit­i­gate prob­lems sig­nif­i­cantly by al­low­ing a de­gree of move­ment to oc­cur.

With re­gard to the ground in­ves­ti­ga­tion work I can only sug­gest you agree ex­actly what the plan­ning of­fi­cer wants and get quo­ta­tions from rep­utable en­gi­neer­ing com­pa­nies for them to carry out the in­tru­sive sur­vey work.

Avoid go­ing di­rectly to com­pa­nies that have a vested in­ter­est in push­ing their par­tic­u­lar ex­per­tise. For ex­am­ple, a pil­ing com­pany will push for a pile foun­da­tion so­lu­tion whereas an in­de­pen­dent en­gi­neer will put for­ward the best de­sign for your cir­cum­stance. Spend­ing a lit­tle now could save in the long run.

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