John Sayers' Recording Studio Design Forum

Hi all,

I have a double garage (pic included) that i would like to turn into a practice/self recording room. I have moved recently to a block of land over 2000sqm, and don't think sound proofing is the big issue out here in Mount Colah, Australia.

Before i determine the make up of the room, i would appreciate advice on how to begin with the floor....always a good place to start.... and the place where my knowledge most fails me. The garage was built and it seems they then filled between the walls with concrete, which is quite uneven by roughly 30mm in areas, and does suffer slight dampness in spots, mostly after rain when the ground is drying out. I would like to raise the floor, but also need advice on how to perform this either via more concrete separated by plastic course, or timber floating floor, keeping in mind using DPM and/or VP's where required.

i am using the larger piece of garage, ... keeping the smaller section as storeage. You can see a corner of the garage is slighty below grade by 2 bricks. If concreting, this could raise it up one brick course or a little higher, and i could always raise the concrete along the inside wall to be slightly higher than grade, therefore depending on DPM/VP to keep moisture from coming up through the floor. i do not want to jackhammer it out and start from scratch!

Timber floor may be easier, but lose a lot of headspace raising it off the floor, using 4x2 floor structure, plus boards plus carpet or floorboards etc.

can those that have needed to do this in basements or garages advise how they have been successful in having a dry floor.

fyi, i do intend on boarding up the inside of the garage, either using timber or steel stud frames, leaving a 1 metre space behind the garage door for gardening tools also.. I have this drawn to scale also, but would like to concentrate on the floor for now. If you need further information on this as it may impact how i do the floor, i can advise if needed.

Is it not possible to reduce the ground level outside so it is below your existing concrete slab?

Thank you for replying.

not really, as that would mean lowering the entire driveway and in other areas otherwise i would form a pool around the garage. However you have given me an idea of how i could better drain it away along two edges and also to think more about how i control outside rather than only inside. Thanks!

The 1st and 2nd pic below is of the garage which is the corner where the ground is raised against the garage wall. The ground is raised 3 brick courses high.





Pic 3 below shows how rain travels down the brick paving onto the pavers/pebbles path, sloping down alongside the rear of the garage until it passes the garage and runs down a hill. On the corner where the pebbles reach the garage (3 bricks high from the main concrete bed foundation), I think i can better slope this left to right away from the garage as it may slightly slope toward the garage right to left.



Is it worth taking up the pavers/pebbles and placing a plastic sheet underneath and against the garage to better keep the ground dryer underneath the plastic, and to keep water away from contacting the brick wall? Therefore the flow of water can continue down this path, but be sloped left to right and better attempt to keep the ground and brick wall free from contact with natural flowing rain water.

Pic 4 shows the paving along the the side of the garage from the rear of the garage to the front which slopes along the garage from rear to front. As you can see, i have taken these pics on a rainy week, and although it stays relatively dry, the dirt underneath is damp. i could remove the paving closest to the garage and do the same along here, ensuring i keep a slope & running the water away from the garage out to the driveway.

The issue you are dealing with is a direct result of no moisture control between the earth and the existing slab. You can not mitigate this, as the poster above alluded to, by changing elevations of the ground around the exterior perimeter...it doesn't matter to condensation and the migration path.

This assumes that there are no penetrations in the structure that rain can get into and collect directly on the top of the slab.


Certainly your safest move is to remove the existing slab and start new, with a proper moisture barrier between the earth and the concrete.

One option would be to incorporate a french drain around the exterior perimeter of the structure.

But the transfer of moisture from the earth thru the slab will still exist. So placing a moisture barrier over the top side of the existing lab and then installing an additional 2inch layer of concrete on it, while still an option, the moisture will still rise to the bottom side of the barrier...and look for a way out.

This presents a problem since the "way out" will be horizontally towards the exterior perimeter walls...and if these walls are wood then rot is going to be the next issue, or if they are concrete or block then you either trap it or it leaks into the block....neither one of theses is acceptable.

If I was really...really...REALLY concerned about it. This is what I would do.

I would cut 12 inches off the side of the slab all the way around the perimeter. Remove the concrete we just cut loose, the 12 inches +/-.

Then I would install visquen plastic as required for my barrier. And then place the new concrete...at least 3 inches over the top of the existing to include the footer area we made.

This would remedy the vapor transport, level the floor and give you a sure area to start your build.


It would ALSO allow you to decouple the existing slab from the interior side of the structure..

_________________
Brien Holcombe
_____________________________________________
Sound: You can't stop it, you can only try to contain it.

Thanks xspace, so I have quickly sketched what i think you mean. The bottom layer is ground, the next is concrete foundation, the next layer is how the concrete has already been raised, the next layer is visquen plastic, then a new layer of cement. The arrow indicates the only issue i can see of moisture squeezing between the plastic and brick wall = minimal.

Also, looking closer, there is obviously an original slab that could well have wire reinforcement through it.




In regards to just laying a moisture barrier down, you say it is an option but then say the issues aren't acceptable.

With the way i will be performing the ceiling and walls (cavity between inner brick wall and internal wall - same for internal ceiling 7 roof), it will allow an all-round airspace except for flooring (unless i do raised timber floor). This will have pretty good access to outside air via the pics shown below as there is a gap between the brick and roof via large wooden beams. Can i place a moisture barrier over the floor like you say in your 5th paragraph, and 200mm up the wall, lay 100mm concrete. Will this suffice to allow moisture to escape? i could also open the garage door anytime to allow air to breeze through the cavity around the walls so the moisture and air doesn't stagnate.

I posted above as the idea of reducing the outside ground level as many old buildings in the UK have a damp course level that if the ground level is higher than this damp course then then damp can come through the walls, also if the existing slab has no damp proofing then this will also get damp coming through the slab,

I understood what you were looking at Rogue...but you did not elaborate It would look on the face of it that (to someone looking at the post in a few years down the road) that the problem was a direct result of the ground elevation and that changing the on the exterior side would benefit the interior side...

It isn't the answer, it may be in part, but only in part. If moisture is coming thru the walls, then the walls are in need of attention, but almost always...it is the lack of a vapor barrier @ ground level that will accumulate condensation on the top side of a concrete slab.

Also, I might add, that reducing the ground elevation on the exterior of an existing slab has the potential to expose the footer to erosion, basically you add gas to the fire that already exists:)

_________________
Brien Holcombe
_____________________________________________
Sound: You can't stop it, you can only try to contain it.