Hello,

I'm doing some green consulting on a church hall that was constructed in the 60s. They basically laid a concrete slab on the ground as the foundation and built the hall. It now suffers from mildew, I'm told because of moisture that sits underneath the foundation, and sometimes leaking into the hall itself if it rains hard enough, although recent construction to the adjacent road has changed the slope of the lot a bit, and the latter is no longer really a problem.

My question is, does anyone have any ideas of green solutions that would either solve the problem, or, failing that, mask the smell, and that would also not cost too much. Someone suggested to me the idea of forced air heating as a way to help keep the hall dry, although it would likely be very difficult, as the hall currently uses hot water radiators. Any thoughts?


Thanks

Thanks for your reply Alton.

I'm not entirely sure about where the water is coming from. My impression is that the concrete slab is the foundation and that there is moisture underneath (that must be seeping up?). Does that make sense? Sorry, not a strong background in construction.

Greetings,

Chances are that you are going to have to tear out the wall dry wall and remove the FG (?) insulation as it will be loaded with mold. Replace FG with a type 3, 2 layer, Radiant insulation (RI). Install a single layer, NON PERFORATED, foil over the studs like a VB, but in this case the foil will act mostly as a barrier to any residual mold spore coming thru. Been there, done that. Another option is to attach 2x2 over the drywall and install the type 3 RI with single layer, NON PERFORATED over the 2x2 and new drywall. You will also have a higher insulation value and no condensation to support mold.
Ck: fifoil.com

Installing the RI will change the dynamics of the stud space in 1st option and allow the cavity to dry out. Mold will not be able to grow. The 2nd option will also change the main wall dynamics as the RI will now be the primary insulator and greatly reduce or eliminate the condensation and moisture content that causes the mold.

Personally, knowing the effects of such a situation, I would want to cut out some 2'x4' sections of dry wall to ck the stud damage before choosing which method to use.

Would be good idea to install a perforated RB on top of the existing attic insulation if possible.

If you remove the drywall you will see the effect the moisture has had on the framing.

Churches' have another problem in that most of the time they are unoccupied do not require heat or ac.
With bulk insulation the building mass and especially the insulation has to absorb or cool off a great deal of energy in order to be come comfortable for services or functions. This results in large energy bills and uncomfortable conditions, especially for those closest to the walls. The RI reacts instantly to the load put on it and the building uses less energy and is more comfortable. I've seen some churches that require several hours to warm up or cool off (somewhat). Not so with the RI.

As far as the floors are concerned I think you will find products on the web that will address that issue.
Polyurethane would probably be the most common to use.

If you haven't already done it I would install some type of drainage around the building, extending at least 24" out from the building. For instance a double 6 mil plastic about 6-8 ins below surface with river gravel or some other smooth decorative rock. Bushes and foliage should be kept away from the building also.

I've made an assumption that this a more or less standard frame building with scissor trusses or other.

Greetings,

I forgot to address the covering up of the smell. You really don't want conditions that allow mold to be present. Far too many people have either minor to clinical reactions to mold. Since you already have mold you don't know if you have "black" mold that can be so damaging and lethal. Also, the mold can spread to other walls in the building. Mold can literally destroy a building, don't skimp.

Thank you for all your advice

In the mean time, seal it up well and run dehumidifiers to keep the humidity under 50%.

Mildew is mold. You have got a mositure problem to cure or the mold will come back.

Back when the building was constructed they would not have poured the slab on polyethelene plastic. Through capilary action any moisture in the ground will be wicked through the concrete. Other sources of moisture could be roof leaks, around windows etc, plumbing leaks.

IF there is a gravel base under the slab keeping it well drained will help. Proper site drainage should be look at. Gutters, down spouts are all things to review.

You will need to determine the source and correct the problem.

It would be easy to drill a hole through the floor and see what is there in terms of gravel and water. Pumps can be used to remove water from gravel.

+1

A coring machine would be good in this application and you can leave the core open (i.e. similar to a sump) and see what type of moisture collects.

If the moisture is deemed to being pushed up through the slab, there are epoxy and other coatings that are designed to stop the hydraulic movement of water through the concrete (at least at the top surface). This will not address any of the moisture where the framing is in contact with the slab so you are going to need address the water at the edges via some of the methods mentioned previously (re-routing of gutters and downspouts, french drain, proper grading, etc).

Bulk water issues are primary- trenching in an perimeter drain ("French drain") with a landscaping fabric wrapped perforated pipe, with the ditch backfilled with 3/4" screaround the outside will lower the overall moisture in the slab, drained to a remote dry-well or a sump if there aren't any other good options.

If there are eaves/overhangs besure that the drip edge is in decent shape, out sufficiently far that is isn't just directing flow on to the surface of the siding. If there are no eaves, a gutter & down spout system may be necessary to direct the water off of the walls and away from the building.

What is the wall construction (timber framed/CMU/other??) What is the finish floor on the slab?

Are you sure there aren't roof leaks contributing to the problem?

Keeping the interior relative humidity under 60% with mechanical dehumidification is sufficient to keep the mold from growing. (Under 50% would only be required if you needed to kill off dust-mites for those with allergies.)