It all started when I discovered that I had high radon levels in my basment. So I asked someone to install the fan to extract the gas etc. and to save some money I thought I would caulk the basement cracks myself. I mean how hard can that be, and so what if it is not the most neat job, it is in an unfinished concrete basement after all.
Well as with all DIY projects it is not as easy as it looks. The issue was a crack between the basment concrete wall and the concrete slab. This crack varies in size between 1/4 inch to almost zero and extends all the way round my basement. About 200 feet.
I start by using SikaFlex self leveling crack sealant. This stuff forms a great seal, but dissapears into a bottom less crack. So after using two tubes of this stuff on like 10 feet of crack and at $US 5 for a 10 oz tube ... time to regroup.
Read somewhere about foam backing rod. OK. go to Home depot and locate some ... way to thick for the crack. Settle on some self adhesive foam roll sealers for doors and windows. This is thinner and at least I have a fighting chance in getting it into the cracks. The adhesive on this stuff is a pain and squeezing it into the crack is slow ... slow .... It does work though and I get like 10 feet of crack done in like
2 hours.There has got to be an easier way. Try some non self leveling crack sealant. Polyeurethane PL Concrete and Masonary. This stuff works, but my hand is falling off. I bought one of those cheap caulking guns ... bad bad move. Next trip to Home Depot buy the best one there is at $US 11. Big difference hand remains in resonably good shape after 80 feet of caulking.
This Polyurethane stuff is great sticks to the concrete well .... that means it also sticks to hands, face, caulk guns. This stuff gets everywhere. Next trip to home depot get some latex gloves. These are well worth it.
After alot of trial and error, I have finally got the magic formula correct.
So the magical tips for anyone wanting to seal a concrete basement for radon is:
1) Get the best Caulk gun there is. Cost $US 11. Your hand will thank you. 2) Get two sorts of Caulk: a) Self Leveling Concrete Caulk, Sikaflex, Polyurethane b) Polyurethane Concrete Caulk. Non self leveling 3) Latex Gloves 4) White Spirits to wash off caulk mess .... 5) Eye-goggles, safety protection. 6) Vaccum cleaner.I do not have any basdement water issues so all I am trying to do it caulk a crack.
Step 1: Vaccum out any loose debris from the crack Step 2: Caulk using the Non-self leveling caulk first. If required smooth over with your finger to get as much into the crack as you can. This caulk basically stops the self leveling stuff dissapperaing into the bottom-less void. Step 3: Go over now with the self leveling sealant. This will close off any small holes for a good gas tight fit. Step 4: If there are any more holes remaining where the self-leveling sealant dissappears into, due to a void below. Fill with a dab of the non-self leveling stuff.
With this technique I found I could make good, if messy progress. Note that both caulks are polyeurethane so that you can apply one on top of the other. I hope they are sort of compatible. So far so good, never did extensive checks on this though.
Good luck, best, Mike.