1,250 lb aquarium on the living room floor?

Vetshep wrote:

"How do I know if my floor can support a large aquarium? Looking to put a glass aquarium (140# empty) on a wood stand (48"×48" footprint) in my 1st floor living room (over the basement). Aquarium would be placed against an exterior side wall. This side wall is poured concrete in the basement. The tank holds 93 g but some of this water will be displaced by rock and sand. There will be another smaller sump tank in the stand which holds an additional 20g. I estimate water at 100g/900#. I estimate the rock/sand weight to be 150#. Stand is 1/2" veneered plywood that is 48×48×48" with fairly bulky trim & shelf on the top but have no idea about its weight. I can send a picture if helpful ... Thank you for your thoughts! "


With the weights that you described you are pushing 80 pounds per square foot within the footprint of the stand. Most homes are rated for only 40 pounds per square foot of superimposed load.  Looks like you will need some additional framing in the ceiling of the basement.  Of course, posts are both the cheapest solution and the most  intrusive solution (at least with respect to keeping the basement area open).  If the ceiling of the basement is unfinished, you may be able to reinforce the joists upon which the aquarium rests with some engineered lumber beams.  We can help you figure out the exact design but it certainly looks like you need to add some support beneath.  Let us know if you need us to evaluate and provide a stamped retrofit plan. 

By the way, yours is a pretty common question.  I'm glad you asked BEFORE you installed the tank instead of AFTER, like some people!

"Cosmetic" cracks in walls?

bbrown wrote:

We just moved to a home that was built in 1994. Our inspector noted "cosmetic" cracks in the walls but it is much more than that. We have low spots in the floors, heaving in corners in some rooms, shifted windows, doors that are stuck and multiple cracks above doors.... a contractor that came out said that everything looked as if it was all shifting to the center of the house. My question is what causes this? He also told me he highly recommended me hiring a structural engineer. 


Thanks for your inquiry.  Assuming your walls are sheathed with sheetrock(gypsum wall panels), cosmetic cracks are typically vertical or horizontal and extend through joints in the panels.  If you have plaster walls (generally much older homes) the cosmetic cracks may be more meandering in direction.  But even "cosmetic cracks" can really be signs of more significant problems when combined with other evidence of movement such as sloping floors and such However, if you have diagonal cracks over interior doorways and the doors are rubbing on the tops of the frames or they don’t latch, your contractor is right and you probably have some movement of the foundations or framing toward the middle of the home.  Not an uncommon phenomenon, unfortunately.  The greatest load is near the center of the home since a home typically has joists and beams coming in from all 4 directions.  The goal is to determine if the movement is old and stabilized or if it is ongoing.  If the cracks appear to be growing in length or if the doors become increasingly difficult to open/shut you probably need and engineer to diagnose the problem and either prescribe a repair plan and/or benchmark the positions of the floors with accurate level measurements and compare the measurements at some future date (I recommend 18 to 24 months).

What's with the cracks in my new concrete walls?

Question from SeekKnowledge:

I am closing on a new construction. Noted 2 foundation stress cracks. One bigger than the other but both under 1/4". Spoke to builder and since it is less than 1/4", they may not do anything. If they do, probably just use concrete to patch. House completed in Oct 2016 and the foundation maybe poured 4-5 months before that. Do not like to see cracks so early. One of the cracks is at southwest corner of the building but that section it is diagonal that runs about 8-10 feet maybe. I am interested to know if this is indicative of anything serious. Thank you. 


Uniform cracks in poured concrete foundation walls and slabs are rarely indications of retaining wall failure or foundation settling.  The concrete expands and contracts through seasonal changes in moisture and temperature and to relieve the tensile forces caused by contraction, the walls or slabs crack.  This is especially true in the early years of a structure because the concrete is still curing (and does for many years) and the initial evaporation of water allows for increased shrinkage.  It is a good construction practice for the contractor to provide joints (grooves formed or cut into the concrete) to control the direction and location of the cracks.  You most often see such control joints in concrete sidewalks or driveways but almost never in residential foundation walls or basement slabs.  In the absence of control joints, the wall or slab will choose for itself where it will crack.  These cracks in walls are typically vertical and regularly spaced anywhere from 6 to 15 feet apart depending on the thickness and height of the foundation wall.  In slabs, the cracks may be meandering but typically extend off the re-entrant corner, such as where the garage bay extends into the basement area.  It is possible that the cyclical movement of the walls may rupture the exterior waterproofing membrane allowing water to enter the basement.  If this ever happens, the cracks should simply be injected with an expansive polyurethane sealant to stop the leaks (around $900 for a 9’ tall wall). 

Warnings: If the wall on one side of the crack is positioned inward relative to the wall on the other side of the crack or if the cracks in the walls generally run horizontally, we really should have a look to help determine if you have a significant structural problem.  In this case, call our office to schedule a structural inspection.

What are my options for removing posts in my basement?

Question from William O:

 We are thinking about finishing a portion of our basement. Our basement has a total of 4 steel columns down the center of it. The portion that we are considering finishing only has 1 of the 4. All 4 of these columns are along the center line of the home and are underneath what appears to be (4) 2x12 boards. My question is, what are my options for removing one and/or all of the columns in the basement?



Good question and a common question too!  Of course the answer is always, "Yes!"  We can design a structural system that spans across the entire basement but you wouldn't like the exorbitant cost... so let's get a bit more practical.  Can 1 post be removed with a reasonable cost?  can 2 be removed?  Many factors are involved: number of stories above the basement, the length of the floor joists that land on the beam, the way the joists interface with the beam, distance between remaining supports in the basement, the available headroom...  

Here are some considerations:
1. If the existing  joists rest on TOP of the existing beam (4-2x12's), removing 1 post should be a reasonable task with reasonable costs.
2. If the existing joists are supported on the SIDE of the existing beam, AND you want to keep the same headroom under the beam, removing 1 post can be a good bit more costly because the old beam would have to be removed before the new one was installed.
3. Removing 2 posts is not a huge challenge as long as they are not CONSECUTIVE posts.  Basically, you would then have 2 very simple beams.  If you want consecutive posts to disappear, the new beam would be twice as long (obviously) but would have to be four-times the strength!

We always try to stick with engineered lumber beams, but on occasion we have to resort to steel because of a long span, low headroom or heavy finishes above.  Changing to steel can add a good bit of costs not only because the material is more expensive, but because contractor's aren't as comfortable working with steel.  Making an contractor uncomfortable will cost you big $$!

As always, if you want a specific design for your home, call us or email us and we'll schedule you for a consultation.

How thick should a slab be to support an outdoor water catchment system...?


How thick should a slab be to support an outdoor water catchment system from rain harvesting and how much rebar if any? This tank is 650 gallons, dimensions are 56" wide by 72" high and the tank is vertical. The tank specs state the tank specific gravity is 1.2 with approx water weight of 9.9 pounds per gallon I had planned on having the tank elevated 10 inches to allow for positive water pressure when irrigating any plants. Thanks


What gives with the water tank questions?

We would like to remodel a second floor fireplace...How can we know if the interior second story wall will support the weight?


We would like to remodel a second floor fireplace (gas insert type) using a synthetic stone veneer. Based on the sample left us by the mason, I've calculated a weight of just over 1,000 lbs. We would prefer this to the Air Stone product, which would weigh approximately 275 lbs. The fireplace sits atop a second fireplace (gas insert type) in the basement. How can we know if the interior second story wall will support the weight?



If the stone is flat against the exterior wall, and it is really just a 2" or 3" veneer, you should have no problem. The weight itself is easily handled by the exterior wall framing. If the fireplace wall and stone cladding are toward the interior of the room and are positioned over joists, the joists underneath will have to be reinforced... not an easy or cheap thing to do!  Give us a call for an on-site inspection if you feel we haven't understood your specific situation adequately.

Are my bookshelves more than just bookshelves?


Hello, I'm interested in removing two bookshelves that exist between my kitchen and sun room. Sounds easy, remove the books first and then the bookshelves, however I'm not sure if the bookshelves are actual columns disguised as bookshelves and have a structural purpose. The bookshelves seem to support a crossbeam that is attached to both walls on each end , but each general contractor who looks at this provides a different answer like...

a) They are just bookshelves, they can be removed including the cross beam which is not a real cross beam. Cross beam exists only to hold the bookshelves vertically.
b) They are just bookshelves, but the cross beam needs to stay since it supports the walls from buckling.
c) Keep storing your books and magazines.....because the bookshelves aren't going away anytime soon.

As you can see I need a structural engineer who can say go or no go on this remodel project. Any help is appreciated regarding next steps.
by the way this is a great service so thank you for offering to answer.



Looks like you are half-way there… the books are gone.


And the answer is…. wait for it… “b”.  At least that’s my $0.02.  I expect that the tall wall has a joint in the middle of it, thus requiring some lateral stability.  Even if there were no joint in the middle that wall is so tall that it really needs a brace in the middle to keep if from bowing inward or outward under the lateral force of winds. 


Now, let’s talk about alternative solutions.  You could get rid of the beam but it would take a bit of work.  We could design a vertical beam (not exactly a post because it will resist lateral forces on the side of the member) that is attached to the ground and to the ridge of the ceiling above.  You’d have to box out around it (see attached very quick sketch) but it will serve the purpose of opening up the rooms.  Quick and easy solution… get rid of the bookshelves and patch up the beam.


Legal stuff: All of this is based on the pictures you sent.  You’d really have to cut some small holes in the sheetrock of the beam and the wall to make sure the framing is as expected.  You didn’t hear any of this from me!

Yet another water storage tank question...

mrwrick wrote:

"I am putting in a water storage tank of 3000 gallons, roughly 26000 pounds full, including tank weight. Dimensions for tank are 8 feet diameter, 9 feet tall, round tank with some concavity in base, thick rim is area of most consistent contact. How thick should my concrete slab be and how to configure the rebar? Thanks"


What is it with water tanks?  For some reason I get this question with minor variations about 6 times per year.  I have a feeling some tank installation company has found a hole in our “system.”  Sorry, buds… we are happy to give some advice but I think we are done being your free engineering consultant!

How expensive would it be to replace 4 4" and 2 6" wood posts with steel on a typical deck?

Wayne wrote:

"How expensive would it be to replace 4 4" and 2 6" wood posts with steel on a typical deck?"


Wayne, Thanks for your inquiry.  Assuming the existing footings are reusable and we are not dealing with a deck that is exceptionally high (let's say, under 15 feet above the exterior soil grade) I expect the costs for each new post to be in the range of $350.  If you need new footings as well, you should expect more like $680 each.   You really need to make sure that the base of the steel posts are above the exterior soil level so that you don't have future rust problems.  Give us a call to schedule a site visit if you need help sizing the posts or evaluating the existing footings.  Hope that helps!

Would moving a wall like this and replacing with a beam be something I would need a structural engineer to develop specs/plans for?

Colin wrote:

Hi, I have a quick question regarding moving basement walls. I am moving into a new home in a few weeks and there is an unfinished area in the basement I'd like to build into a small Home Theater. There is a wall in the middle of the room that I am assuming is load bearing.

My question is, would moving a wall like this and replacing with a beam be something I would need a structural engineer to develop specs/plans for? I am new to basements so am not sure if this is required or not.

Thank you for your time, it's much appreciated!



Colin, thanks for the great question!  Based on the pictures, it looks like the wall in question probably IS a loadbearing wall.  Though I do not believe the code requires that you hire a structural engineer to size the beam, it is a good idea to retain the services of a design professional for two main reasons:

1) You want to make sure the beam is properly sized for your specific situation.  You can find tables online that will help you size a beam but they are only applicable for the most generic situations.  We literally make a living designing repairs for beams that were specified by a contractor who has been "doing this for 30 years!"  Bottom-line, you will probably be calling an engineer either before or after you put the beam in.  Let's get it done right the first time!

2) A structural engineer typically will carry a comprehensive liability insurance policy that protects you if there's a problem with the beam design. 


Hope this all helps!  Give us a call or shoot us an email if you need further input. 

What is the proper layout to build a concrete patio for a slab house in Georgia with the heat?

KC wrote:
What is the proper layout to build a concrete patio for a slab house in Georgia with the heat? Does it require 2" inches gravel or no gravel, wire mesh vs rebar and 4" concrete? What is the differences with 3500 psi vs 4000 psi and 5000 psi concrete mix?

Great questions, KC! I apologize now for the lengthy response but that's what you get when you ask 6+ questions at once! For a residential concrete patio, you don't really need a gravel base unless you have perpetually wet soils or other moisture problems on your property and need some drainage. If you are enclosing this patio, make sure you treat the underlying soil with an approved termite chemical, lay down a 6-mil plastic vapor barrier before you pour your slab. The perimeter should transition from a 4" slab to a minimum 12" wide x 12" deep "thickened" slab. Per the building code, the footing should extend a minimum of 12" below the exterior soil level… this keeps the bottom below the "frost line" and will prevent the footing from heaving upward in one of our cold snaps. Don't forget to add (2) #4 (1/2" diameter) reinforcing bars along the length of the perimeter footing. The proper type of wire mesh is perfect for your 4" slab. No need to go with rebar. For your purposes, a standard 3,000 psi concrete mix will be fine. Higher strength concrete would be used for surfaces that are subjected to high wear-and-tear such as in a warehouse, etc. It would have to be one heck of a party to wear out your 3,000 psi concrete patio! Beware of the contractor that adds gallons of water to the concrete mix when the truck arrives! Diluting the concrete to make it "easier to work with" or to make it "go farther" will lead to weak concrete that will crack and wear quickly. That's the gist of it! Call us if you need more information.

I am building a pole barn and am ready to pour a concrete slab. The structure has been built on a slight slope so I had some dirt fill brought in and compacted...

MJ wrote:
I am building a pole barn and am ready to pour a concrete slab. The structure has been built on a slight slope so I had some dirt fill brought in and compacted. The deep end of the fill goes down about 30". The frost line in my area is 4'. Is it possible to drive rebar down below frost line, then bend it over into the concrete to prevent possible settling later on?

Thanks, MJ for the question. Driving rebar into the soil is a big NO-NO (though many contractors do this when placing rebar in footings). Remember, the rust process is electrical (called oxidation). When you drive rebar into the soil, you provide an "electrical connection" to the ground through which electrons may flow. The result... RUST IN THE REBAR. When rust is allowed to continue, the rebar will expand (rust expands to 1,000 times the original steel volume) spalling the concrete and accelerating subsequent oxidation. You've got to get the bottom of the footing below the frost line, not to prevent settling, but to prevent frost heaving the footing upward. If it's interior space, you should also provide some rigid board insulation between the sides of the footing and the soil. This limits cold concrete inside the building that can lead to some real heating problems! Sounds like you need a properly designed concrete sub-wall (30" above the ground and 4' into the ground). You must be way north of the Mason-Dixon line!

I need to replace a portion of a concrete slab that is used occasionally to play shuffleboard & basketball....

AG wrote:
I need to replace a portion of a concrete slab that is used occasionally to play shuffleboard & throw a little basketball. 
I received a quote that included 3500 psi with fiber for a 16' x 20' section with a price of nearly $3800. 
The original slab has cracked & needs to be removed & a little more fill dirt brought in. 
My questions: 
1. Do I really need 3500 psi with fiber? This slab gets very little traffic. 
2. Does this price sound high for North Carolina area? 
It includes removing & hauling off the original, filling in shallow cracks, & sawing a joint across the concrete.

AG, let's first talk about the concrete strength. 3,500 psi is a bit overkill for a basketball/shuffleboard court. However, the price difference between 3,500 psi and the more standard 3,000 psi should be very small for the amount of concrete you need (approximately 4 cubic yards). Don't consider this a "premium" upgrade. Now on to the reinforcing... Fiber reinforcing will leave you with a "hairy" surface (from the fiberglass fibers that stick up) that may rub smooth in the high traffic areas after continued use. I can't imagine this would be good for shuffleboard. Don't let anybody fool you, sealing the concrete will only delay the "hairy" appearance. I like fiber reinforced concrete in applications where it will be covered with another material such as carpet, tile, VCT, etc. I suggest you use wire mesh (6x6-W1.4xW1.4) that is placed on concrete bricks so that the mesh is in the middle of the slab, not placed on the dirt and "pulled up" by the concrete guy when he pours (that NEVER WORKS). The slab should be a minimum of 4" thick, the fill dirt should be mechanically compacted (fill 8" and compact, fill another 8" and compact, and so on) and the joint should be cut as soon as the concrete is hard enough to walk on (8 hours or so). If this slab is poured on good, tight soil, you should have no problems for many, many years. Pricewise... it may be a bit high, but if you asked ME to cut and remove the slab, haul in dirt, compact it, pour a new slab and screed it... I'd be charging 3X that amount! It's hard work! 

Is it better to put #4 bar 18" on center or 6 gauge wire mesh in 8" thick slab that will see heavy industrial traffic?

No Screen Name wrote:
Is it better to put #4 bar 18" on center or 6 gauge wire mesh in 8" thick slab that will see heavy industrial traffic? 

The answer is NEITHER. You either want to use #4 at 12" on-center or #5 at 18" on-center for an industrial traffic slab. 6 gauge wire is only 0.162 inches in diameter which, when welded at 6" on-center, gives you 0.0412 square inches per foot of slab. You need 5 times that reinforcing! #5's at 18" gives you 0.207 square inches and #4's at 12" gives you 0.200 square inches. Skimping on the reinforcing now will be very costly later when you have to rip out the cracked, shifted slab!

How thick should a concrete slab tank base be to support a water tank holding 5000 gallons of water?

Jaytee wrote:
How thick should a concrete slab tank base be to support a water tank holding 5000 gallons of water? 

Thanks for the question. The answer depends on the size of the tank's "footprint" and the method of support. Let's assume the weight of the water and tank is around 44,000 lbs. If it is a rectangular tank... say 10'x10'x6' tall, an 8" slab (properly reinforced) would be fine. If it is standing up on end... say 8' diameter and 13' tall and resting on 4 legs, you have an 11,000 lb load at each point. You could then use a thinner slab and just thicken the concrete to around 12" (properly reinforced) at each bearing point. Hope that helps. If you want to convey additional information, I could more specifically answer your question!

how thick sould the concrete base be for a 5000 litre water tank and what reinforcing and ratio mix be PLEASE HELP

woman DIY wannabe wrote:
how thick sould the concrete base be for a 5000 litre water tank and what reinforcing and ratio mix be PLEASE HELP 

Woman DIY Wannabe,
(interesting screen name!) since most of us engineers still use imperial units I converted 5000 liters to 177 gallons which weighs 11,018 lbs. This is not much weight when distributed across the footprint of the tank. Most tanks actually sit in some sort of frame with legs attached to the ground. Some rest directly on the concrete which further distributes the load. So... worst case scenario, with the tank resting on 4 legs, the weight on each leg is around 3,300 lbs (adding the weight of the tank itself). I'd suggest a 5" thick concrete slab reinforced with welded wire fabric of 6x6xW2.0xW2.0 (that is, 6" wire grid with 8 gage wire) laid in the middle of the slab depth (support the wire with chunks of concrete bricks). This, of course assumes you have good, tight soil to rest the slab on. You can use a standard 3,000 psi commercial concrete mix or sack concrete from your local hardware store. If you are a true DIY'er and are mixing your own concrete, make sure you mix in the amount of water listed on the bag. Go ahead and schedule an appointment with a chiropractor because mixing concrete can be back-breaking work! Good luck with it!