Water leak between sill and concrete pad

Question

I'm repairing a three season room. I took it down to the studs, put in new sill plates and sliding glass doors.

For the sill I put down Protecto wrap, latex caulk, a pressure treated 2x4 and secured to the pad with tap con concrete screws. I used a latex caulk on the outside of the 2x4 after it was secured.

Water is getting through during heavy rain in two places. It appears to come from under the sill, at the center post and the door on the right.

The latex caulk appears to be cracked.

There's no gutter so all the rain water ends up at the edge of the pad. But it is on a hill so the water should be draining away fairly quickly.

I still have to put the bottom trim on, under the door frame, in front of the sill.

Should I make sure there are no leaks before putting the trim on? Or, will the trim make it water tight?

With the latex caulk cracked, can I go over it with a silicone all weather caulk?

Answer 1

Although you may not see any water penetration after installing the floor molding it would be wise to first repair the source of the water entering the room.

The initial step is to divert as much of the rain water away from the wall. Gutters, as you mentioned, will help a lot to do this. Extend the downspout several feet from the wall base to ensure all water sheds away.

Next, applying a 100% silicone or urethane caulking along the sill or bottom plate/floor seam may prevent any water the gutters can't handle from seeping inside. You should try to remove any latex caulking first. Then apply the new caulking and press in to seam with a putty knife.

If you can pinpoint the precise entry of the water and open the wall to access the sill, it may be possible to surgically remove the section of treated lumber (if not above a stud). Once removed apply a copious amount of silicone and secure the plate and the edges of the existing plate with TapCons.

I've noticed when I use TapCons that it help to drill a slightly over-sized pilot hole so that the screw grabs the concrete rather than the wood first. This prevents the screw from raising the wood slightly before securing to the concrete. Also, a light tap with a hammer on the wood after the screw is set will ensure the board is completely flat against the concrete.

Answer 2

Based on your pictures, there is a major, fundamental error in play that you are fighting against: the concrete slab upon which the exterior walls rest protrudes several inches beyond the walls. Concrete is porous and redistributes moisture within itself. When the part of the concrete pad on the outside of the building gets wet, the moisture contained within will tend to migrate inside, towards dryer conditions. Additionally, standing water on the part of the concrete that's outside will inherently pool against whatever is sitting on it separating interior from exterior: your sill plates. Caulk is doomed to fail here.

In a nutshell, your goal is to make sure that there is no part of this room's concrete slab is effectively outside. Without substantial demolition work, is is too late to correct this error in the ideal way: by extending the exterior walls themselves a few inches so that there is no concrete protruding beyond them. I imagine you don't want to undo all your work to do this. You have a couple of remaining options that I can think of:

1. Cut off the exposed concrete with a huge concrete saw.

2. Seal the exposed concrete with a waterproof material like tar, asphalt, or a liquid-applied waterproofing membrane, and then protect that with something that can withstand UV radiation and foot traffic.

3. Extend the thickness of the walls with rigid foam boards and furring strips to completely cover the exposed concrete. This looks like it would be difficult with your sunroom because most of the walls are actually windows, but it is still possible--your windows would simply have large and deep exterior sills. This could be a very nice look, in fact.

There also appears to be a secondary error at play: your wall appears to have no water-resistive barrier. This is typically Tyvek or tar paper. The wall's sill plate should not simply be exposed to the elements like that--pressure-treated or no. A strip of Protecto-Wrap is not a substitute for a proper WRB, especially in an application like this where it's basically at grade. You need to to protect the wall from water by applying some sort of WRB material over the sill plate and the sheathing, integrated with the flanges of the windows and doors, and continued down all the way to the ground. At this point, the most effective thing may be a liquid-applied membrane of some sort or else strips of window flashing tape, like more Protecto-Wrap. The tape is not cheap, but you don't actually have much wall to cover.