Sealing GRP to concrete base

Forums General Discussion Observatory wall sealants Sealing GRP to concrete base

Alan Snook

I used 3M 4200 marine adhesive sealant when I set up the 3.5m dome (see small ads in the back of JBAA Dec 2019). This was at the recommendation of the dome manufacturer – Sirius in Australia. Get it from some chandlers. The bottom edge of the GRP panels was abraded a little with wet ‘n’ dry to key the surface. I did the work in Sept 2020 and so far it has kept the water out. I got through three tubes of the stuff. However I fear your joint may now be contaminated with mastic, window sealant etc; you will surely need to remove all traces from both the GRP walls and the concrete before using the 3M product or it will be good money after bad,