backfill for masonary wall
backfill for masonary wall
(OP)
Hello,
I have a basement wall (load bearing side) that has cracked 75% of it's length horizontally 5 ft from the floor and has bowed in approx. 2 inches at midspan. This has happened because of two factors, highly expansive clay backfill and freeze/thaw cycles (Buffalo, NY). Outside I dug the length of the wall down to the footing and pushed the wall back to nearly plumb with some braces. Once the wall is all the way plumb (another 1/2 inch to go) I plan on repointing with 10,000 psi tensile epoxy mortar and building five pilasters anchored to the footing.
Question: What can I use for backfill? I do not want to use the clay I excavated. I have heard all kinds of answers, none which seem very good, from concrete to compacted granite. Any ideas?
I have a basement wall (load bearing side) that has cracked 75% of it's length horizontally 5 ft from the floor and has bowed in approx. 2 inches at midspan. This has happened because of two factors, highly expansive clay backfill and freeze/thaw cycles (Buffalo, NY). Outside I dug the length of the wall down to the footing and pushed the wall back to nearly plumb with some braces. Once the wall is all the way plumb (another 1/2 inch to go) I plan on repointing with 10,000 psi tensile epoxy mortar and building five pilasters anchored to the footing.
Question: What can I use for backfill? I do not want to use the clay I excavated. I have heard all kinds of answers, none which seem very good, from concrete to compacted granite. Any ideas?





RE: backfill for masonary wall
RE: backfill for masonary wall
RE: backfill for masonary wall
The clay you took out will work, it just must be replaced with appropriate moisture and compaction, and the drainage away from the building must be positive.
RE: backfill for masonary wall
HTH,
Carl
RE: backfill for masonary wall
Good luck.
RE: backfill for masonary wall
How about using some thick rigid insulation board on the walls, then backfilling with crusher?
RE: backfill for masonary wall
RE: backfill for masonary wall
Have you thought of ways to avoid backfilling at all?
Beware of using "filler boards". If you backfill the clay against these, then they will just transmit the pressure to your wall. If the boards are compressible, they might do the trick, but I don't favour them in this context.
The pressures you have to deal with if you backfill are:
1) Static soil pressure.
2) Water pressure.
3) Pressure induced in the soil during compaction of backfill, and some of this may be "locked-in".
4) Swelling pressure from the soil as the soil expands in moist conditions.
The wall was probably originally designed to resist "normal" soil pressure, but it has since been weakened.
Drainage will reduce the water pressure if the water can reach the drain, for example, through a granular backfill.
If you use an appropriate granular backfill, compaction forces will be minimal.
To avoid swelling pressures from the soil, you either have to stop the soil from swelling (-very unlikely-) or separate the expanding soil from the wall. If you use a ROUNDED pea gravel, the force transmitted through will be slightly reduced.
Other ideas will occur to me and other readers after I post this, but I hope the above is useful.