Intelligent, effective solutions for joints (8/8) – Old floor joists in refurbishment projects

Continuation of Part 7: Particular challenges on refurbishment projects

Old floor joists in refurbishment projects /penetrations of masonry/joists

Typical leaks can be found at the joist bearings of timber roof joists in the masonry structure. The bricks between the joists are generally not plastered. On refurbishment projects, joints with the old masonry can lead to leaks; on new buildings, non-mortared butt joints between bricks can cause leaks. Even if a layer of plaster has been applied, airtight joints to the joists are generally neglected. This is indicated by air currents through the joints between old wooden floorboards detected during blower door tests.

This series of articles summarises typical, challenging joint situations and shows how technicians can find practical solutions for these challenges. It also provides an overview of the detail features for which prefabricated solutions are available that allow tradespeople to achieve airtightness in a quick, easy and reliable manner.

Air entry through the joints of these old wooden floorboards is indicated by the bulging of this sheeting during a blower door test. The causes of this problem are joist penetrations in the floor area and/or unplastered masonry areas.

Summary: detail features are becoming more sophisticated

A good, careful tradesperson can still find a solution for all situations using adhesive tape and adhesive from a tube. Prefabricated elements provide planning certainty and guarantee quick, cost-effective installation.

Prefabricated solutions and solutions implemented by tradespeople for joints on new buildings and refurbishment projects.

Overview of the series

  1. Typical leaks: cable feed-throughs for electrical (released on June 3rd 2020)
  2. The challenge: sealing cable looms (released on June 10th 2020)
  3. The challenge: cables passing underneath joists (released on June 17th 2020)
  4. The challenge: pipe feed-throughs (released on June 24th 2020)
  5. Care required at the corners of plastic windows (released on July 1 2020)
  6. Problem with skylights: adhesive bonds at corners (released on July 8th 2020)
  7. Particular challenges on refurbishment projects (released on July 15th 2020)
  8. Old floor joists in refurbishment projects (released on July 22th 2020)

This Series was wirtten by Jens Lüder Herms and Holger Merkel

Jens Lüder Herms, Zimmerer & Diplom-Ingenieur (FH), Exportmanager und Anwendungstechniker

Jens Lüder Herms, carpenter and graduate engineer, Export Manager and Application Technology specialist, pro clima Research and Development,, He provides insights into his work on Twitter and Instagram.

Holger Merkel, Blower-Door-Messdienstleister, Referent der pro clima Wissenwerkstatt und Leiter von Zertifizierungskursen

Holger Merkel, Blower-Door-Messdienstleister, Holger Merkel, provider of blower door measurement services, speaker at the pro clima Knowledge Lab and instructor for certification courses.. He has documented examples of leaks in his most recent project He also publishes specialist articles on issues such as blower door tests on

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