This client requested a Timberwise survey for a commercial Café Nero property in Llandudno, North Wales. This building is a corner retail unit with an adjoining mobile phone shop of brick and stone construction. The property is empty on the upper levels, and the weather was overcast but dry at the time of inspection.
The survey was restricted to the upper levels of the property to check for a case of dry rot (Serpula lacrymans). In this instance, there was a rom where there was no safe access point and was only highlighted when the technicians were taking back the floor joists and a ceiling fell, exposing the small room below, which contained stacking shelves and debris. The room below was understood to be a bathroom with tiled walls and was located on the floor above the bottom floor of the mobile phone shop.
Observations
The only injection point our technicians were able to gain a viewpoint on was in the former second floor kitchen, where the floor had been repaired. The wall plaster on the external elevation and returning left wall were affected by salting action, a result of penetrating damp from the external source of the fungal outbreak.
On the landing between the varying floor levels, bricks were removed enabling a glimpse of the floor joists. Decay by dry rot was affecting joist numbers 1 – 4 inclusive and above to the proximity of the box sash window, will put the timber lintels also at risk of decay, which will have to be renewed in a more solid form.
Dry Rot Outbreak
The cause of the attack was determined to be defective rainwater goods allowing water ingress into the fabric of the property. Wooden joist number 1 was noted to have had mycelium spreading across it onto joists 2 and 3 via the lath and plaster.
Dry rot spores are considered to be omni-present and no environment is considered to be free of them. The spores will germinate and grow in timber with a moisture content of between 20 – 30%. The fungal thread (hyphae) digests the cellulose and hemicellulose fraction of the wood but does not attack the structural lignin.
The hyphae remains as a brittle matrix which cracks into cubes and differential stresses. Cuboidal cracking is also characteristic of many wet rots and does not automatically indicate the presence of dry rot. Fungal hyphae may clump together into a variety of structures known as mycelia which takes carious forms depending on the surrounding conditions. They may fill a humus cavity as a cotton wool like mass or grow across the surface of the timber as a grey or white skin.
Active dry rot has a fresh white or greyish appearance. Some hyphae group together to form conducting strands. Their main function is to conduct nutrients through inert non-nutrient material i.e. brickwork, to permit the eventual colonisation of the timbers. The relatively impervious outer layer, together with an unusually alkaline tolerance, allows them to survive in the mortar layers of the masonry. In an infested area, the walls may be full of dry rot strands hence the usual requirement of plaster removal and wall sterilisation.
The dry rot fungus may tolerate relatively lower moisture content and, through this and after facets of its biology, it is potentially capable of considerable destruction.
Recommendations
Timberwise technicians recommended several works to repair the damage caused by the dry rot outbreak and to protect the structure against future potential moisture ingress.
Technicians would cut back the floorboards to joist number 5, beyond the affected timbers. Decayed material would be cut back from joist number 1 to clear the area of decay. New sections of joists would be installed using steel bolts and connectors to secure the new sections together, alongside protecting the cut ends with preservative and wrapped in DPM. All joists would then be treated with a fungicidal solution up to 1m² and beyond.
A toxic box would then be formed around the affected areas. From 12mm to 16mm diameter holes would be formed at 450mm staggered centres to a 300mm wide band to the periphery of all walls that are in excess of 150mm thickness. A similar toxic barrier would be formed around any openings formed in the wall i.e. window openings and door openings. LingaTek fungicidal treatment will be applied to each hole together with surface application to the perimeter of the affected walls. All treated areas previously plastered would also be re-plastered in accordance within standard specifications.
Results
Our surveyors conducted the survey to the fullest extent possible, despite restrictions within the property, and recommended a professional and well-tested series of works backed by over 50 years of industry experience and PCA-qualified surveyors.
Do You Need Help with Commercial Surveying?
Our dedicated and experienced North Wales team is ready to talk to you about your options for property preservation. Don’t hesitate to call at 01492 849 056 or you can request a survey online.
