I would like to know how to fill a large gap between wood and cement. I have attached some pictures. This is outside on the front covered entry. I am going to try and fill the gap so that rain water does not seep through the gap. Two long boards are nailed to the beams that support the roof over the entry. They are above the cement walk. There is an uneven gap between the boards and the cement. I was going to put closed cell backer rod in the gap and then caulk it with Sika Self-Leveling Sealant which was suggested by an employer at Lowe's. My problem is, what kind of material can I use to make a form so that the sealant doesn't run all over the place on each side of the boards as I am applying it? Thank you so much. BillieGap between boards and cement Another angle

  • Sika flex self leveling sealant will not work on that. It is made for gaps on flat, somewhat level horizontal surfaces, sidewalks for example. – Jack Jul 1 '16 at 4:15
  • thank you Jack. I was thinking that I have the wrong sealant when I saw videos of the use of Sikaflex. They were all using it on driveways etc. Don't know what kind of waterproof caulking I should use. Have to go to a contractor somewhere and ask a bunch of questions I guess. – Billie Jul 1 '16 at 18:51

DMoore is right, if you have a grading problem you should get that fixed if you can afford it.

That said, in your other comment you mention that its just water blowing in? If the water drains toward the wood normally and you only flood because of wind blowing it in, I would definitely not plug the gap. Get a piece of plastic trim and screw it to the outside of the wood. Cut out a few notches for drainage.

  • No grading or sloping problem, just water standing in the front entry when it rains. I just can't explain good enough I guess. The plastic trim is a very good idea Levi, but the board is about 2 inches inside from the edge of the cement and I would have to seal the bottom of the plastic some way to keep it from leaking. – Billie Jul 1 '16 at 18:51

I am almost positive that this gap was left there to let water OUT. I would not fill it. If you do want to fill it and potentially cause other issues, just use masonry caulk.

  • DMore, We have to fill it because the rain is filling the cement around our entry door and we can't use the entry for all the water. Filling it would stop so much rain from blowing in under it. The gap is too big for just a layer of caulking I think. – Billie Jun 30 '16 at 23:26
  • 2
    So your patio is sloping towards your house? - that is the real issue. – DMoore Jun 30 '16 at 23:27
  • No. the patio is not sloping. The water just gets it all wet when it rains. – Billie Jul 1 '16 at 18:51
  • The patio should be sloping out. If it gets wet and stays by house you have a slope issue. – DMoore Jul 1 '16 at 19:10

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