Advice for Home Owners

UPDATE:

One solution to reduce the vulnerability of your house is to have your foreman properly trained.  I now offer a training course that will lead to participants receiving the Diploma of Walbrent College.  See article on  Walbrent College for further details.

Regards, Grenville

END UPDATE

I have come to the unfortunate realization that we are doomed to experience the misery and economic setback that other Caribbean islands experienced after being examined by major hurricanes.  These countries only paid attention to building standards after their buildings were weighed in the balance and found wanting.

I have given up hope that the Town Planning department will accept their responsibility to ensure that houses are both designed and built properly, until they actually see the devastation that they could have prevented.  I have also given up hope that the Ministry of Housing will accept its responsibility to ensure that their proposed 2,500 “units” will be anything but sub-standard.

During the past 12 years, I have rarely seen a house built that confirms to the minimum structural requirements of our national building standard.  It is very distressing to report that every one of those sub-standard houses could have been built properly at no additional cost.  There seems to be a strange belief among builders and homeowners that they can somehow realize good quality construction by simply wishing it to be so.

How did we get to this sorry state?  The start of this current building boom saw inexperienced persons offering themselves as building contractors.  This was a well known practise, and therefore it was critical that building standards be effectively enforced.  Fortuitously, the Barbados National Building Code had been published approximately 2 years prior; however, for some inexplicable reason, the inexperienced builders were not required to comply with these minimum building standards.  A timely opportunity was therefore squandered as the relevant authorities refused to accept advice continually offered during the past 12 years.

I have decided to no longer publish articles on the substandard building practises in Barbados.    If there is a single builder in Barbados building structurally safe houses, then please contact me and I would happily publish the construction photos and promote your business free of cost.

I will use this final article on substandard building to inform home owners of what to look for and what to do if they find it.  Most of the photos were taken within the past week.

img_1756.jpg

This is a good start.  Found the building on solid rock.

topsoil.jpg

Notice the layer of topsoil at the surface.  This will compress, therefore do not allow your builder to build upon it.  If he insists, then dismiss him.  The underlying layer is a mixture of predominantly clay and gravel sized soil.  The clay will compress, but it might also swell if it gets wet.  To avoid the risk of the building settling or rising, you should found the building on the rock.  If you do not believe me, then believe the Great Master Jesus who noted that wise men build their houses on rock if they wish them to survive natural hazards.  I believe that He indicated that you are just short of an idiot if you allow your builder to do otherwise and expect the same result.

img_1733.jpg

The builder has excavated to rock, then placed fill on the rock and compacted only the top layer.  The builder will try to justify doing this by stating that it will give him a relatively flat surface upon which to build.  However it is in violation of the building code and introduces the unnecessary risk of uneven settlement.  If he does not found your house upon the rock in accordance with Jesus’ advice, then dismiss him and find a builder who believes.

img_1667.jpg

You should have your builder drill down at least 3 m (10′) to ensure that you are not on a cap rock or over a void.  Remember, we do live on a predominantly limestone island.

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img_1723.jpg

The thickness of the footing should be at least 200 mm (8″) for a single storey house and 250 mm (10″) for a two-storey house.  Here we have 150 mm (6″), and below it is 100 mm (4″) which is clearly insufficient.  If he does not rebuild this properly at his own cost, then dismiss him.  You will save yourself a lot of unnecessary grief.

img_1719.jpg

This concrete was not compacted properly, and a condition known as honeycombing is the typical result.  This honeycombing can provide a path for moisture and air to reach the reinforcement and facilitate its corrosion.  If he does not correct this at his own cost, then dismiss him and find a responsible builder.

img_1721.jpg

Here, there is insufficient concrete cover protecting the reinforcement so that its corrosion is almost guaranteed.  If he does not repair this at his own cost, then dismiss him and find a responsible builder.

img_1722.jpg

Regrettably, this will soon be covered up and the home owner will be unaware that the foundation is sub-standard.  Within a few years later, this home owner will be calling for an Engineer to find out why the house is cracking up.

img_1716.jpg

If this is what your builder is doing, then ask him to redo it properly.  If he refuses, then dismiss him.  Why needlessly put your family at risk during an earthquake or hurricane because of his substandard work.

img_1718.jpg

Partial knowledge is just as ineffective.  He filled the block’s cores correctly, but did not include the reinforcing bars.

corner-block-detail.jpg

This is what you want to see.

img_1770.jpg

Here, the builder has only one side of each window opening reinforced.  I do not believe that he is intentionally doing work which he knows to be substandard, rather, I believe that he simply lacks the knowledge.  That is why the failure to require builders to follow national building standards is such an unnecessary tragedy.  BNBC 2.425.5 (b) specifies one 12 mm diameter bar either side of each opening.

img_1728.jpg

This house is likely to be structurally unstable during a hurricane or earthquake.  Over 90% of houses built during this building boom are similarly structurally unstable.  They are not expected to survive the first major earthquake or hurricane.

img_1753.jpg

I cannot blame the builders for this structurally unsafe practise, for they are simply building what is on the approved plans.  The fault lies with the inexperienced architects and draughtspersons who designed the houses, and with the Town Planning Department who should never have approved the sub-standard designs in the first place.  Unless your house has been designed by a structural Engineer, it should comply with the specified minimum structural requirements of the Barbados National Building Code (BNBC).

shear-elevation.jpg

plan-shear.jpg

The BNBC (section 2.405.8) specifies that external walls must have shear walls to resist lateral forces from Earthquakes and Hurricanes.  These are to be one 3 m (10′) wide wall from foundation to roof level at each face of the house, and it must not contain any window or door openings.  If one 3 m wide shear wall is inconvenient to the design, then two 2.0 m (6′-7″) wide ones are permitted.  You are welcome to look in vain for such houses built during the current building boom.  What is more distressing is that to accomplish this would have cost all of $0.00.  You should therefore review your drawings and get the designer to make the necessary corrections with dispatch.

img_1738.jpg

This is where a lot of damage is done.  There are basically two types of high tensile steel reinforcement that have been used during this building boom, the British Standard BS 4449 and the American Standard ASTM A615.  Since the American steel is 85% cheaper, builders prefer it.  However, one cannot simply substitute one type for the other.  The British steel is approximately 10% stronger; therefore if you want to use the American standard, you need to use more of it which makes the cost approximately equivalent.  In the photo above, the link ends should be bent into the beam.

img_1709.jpg

The structurally unsafe aspect of the American steel is realized when it is bent around radiuses specified for the British steel.  The American standard steel needs larger radius bends and tends to fracture when bent around smaller radiuses.  This means that the beams and columns will likely be ineffective when they are needed most.

img_1711.jpg

This is how roofs are typically built in Barbados and it complies with the BNBC.  However, it is vulnerable to high winds.

Concrete Block Wall House

This is what happened in Grenada during hurricane Ivan in 2004.  I informed the relevant authorities that it was found to be ineffective near the start of this building boom.  However, to-date, they have not issued the necessary errata warning persons not to use it.  If your builder insists on using this roof connection, then insist on hurricane straps.  Ensure that they are made of stainless steel in order to avoid corrosion and their subsequent replacement.

roof-fixings.jpg

Make sure that the frequency of roof connections are increased at the eaves, gable ends, apex, and hip ridges.  They should be at most 150 mm (6″) apart in the shaded areas and at most 300 mm (1′) apart in the clear areas.  Finally, do not pay your builder until he has built each stage of your house properly.

Best regards,

Grenville Phillips II

Related articles by Grenville Phillips II:

500 More Substandard Houses

The Construction Horror Show

Can We Achieve Affordable Housing in Barbados

The Worst House that the Code Will Allow

Weapons of Mass Destruction

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40 responses to “Advice for Home Owners

  1. Pingback: A Must-Read Article By Structural Engineer Grenville Phillips II « Barbados Free Press

  2. Terence Bickley

    Thank you for the information this should be published in the national news papers for all to read,not the inquisitive few.
    Looking forward to the next report.

    ————–
    GWP Responds
    Hi Terence:

    Some useful advice for affordable housing will be provided in the Nation’s business Monday. I will try to provide a link to it tomorrow, otherwise, I will post the information here.

    Regards,
    Grenville

  3. Thanks for posting the information which is very educational. One question, In the corner detail shown can the steel that is shown holding the 3 12mm bars together be replace with brickforce????

    ————–
    GWP Responds
    Hi Novice:

    The BRC brickforce should be used in addition to the 6 mm (1/4″) diameter reinforcement tying the vertical corner reinforcement. However, they should not be used in the same horizontal mortar joint.

    Regards,
    Grenville

  4. Actually I always felt that most builders don’t have a clue when building and I normally end dismissing them. A good example is the overhangs you see being done by imported cheap labor. I will place this information on my website http://www.coopmed.com which is a website which promotes Barbados Credit Union insurance products. Most houses built in Barbados are designed to provide shelter from sunlight and normal rainfall.

    —————
    GWP Responds:
    Hi Mac:

    While I advocate that persons who are building dismiss their builders if they refuse to comply with our national building standards, it is important that the builder be aware of the standard required before he proposes a construction cost. I have found that most builders sincerely do not know the national building standards.

    Regards,
    Grenville

  5. Pingback: Structural Engineer Grenville Phillips Hits Brick Wall «

  6. thanks. What about drilling down 10 ft? What kind of equipment do they use to do this and how costly is this?

    ————–
    GWP Responds:
    Hi Novice:

    You should be able to rent a Hilti drill with sufficient bit extensions to make up the 3 m (10′). You should be able to rent the Hilti drill and bit for under BD$200 per day. If the rock is very hard, then you should be able to rent a core rig with bits and extensions for under BD$400 per day.

    Regards,
    Grenville

  7. “This is how roofs are typically built in Barbados and it complies with the BNBC. However, it is vulnerable to high winds.”
    How do you suggesst that roofs be built?

    ————–
    GWP Responds:
    Hi Novice:

    The BNBC (Figure 2.405B) allows hurricane straps as an alternative. I would therefore recommend the BRC Truss Anchors or equivalent. You can see a sample if you download item 7b under the Technical Data Sheets in the following link to BRC’s web page.
    http://www.brcwestindies.com/technical_manual.html

    I recommend that you use the stainless steel anchors which cost BD$5.26 each. The galvanised ones, which cost BD$3.39 each, will eventually corrode.

    Please be advised that I have no financial interest in BRC whatsoever. However, I do have the test results for their products and recommend them on that basis.

    Regards,
    Grenville

  8. I know nothing about building and frankly the photos of stratified rock and soil has me just as dumbfounded. I always had difficulty looking at a two dimensional plan of a house, so I think I would have great difficulty assessing whether good standards are being maintained. Shouldn’t we hold builders liable for these failures by legal ordinances and check them through the Town and Country Planning Committee? And should theses law be maintained in the interest of society and each individual.

    National Building Code

    No standards, that’s what troubles me
    And yet there is a Town and Country Planning Committee
    This Committee should ensure that we build
    In keeping with guidelines and standards fulfilled
    One has to wait so long to get
    Notarized by them and yet
    A building can have sub-standard design
    Liability should fall on the authority we assign
    Builders should be monitored by one committee
    Useless to leave standard checks for you and me
    I should be able to build with unfeigned confidence
    Let the professionals answer to their imprudence
    Designer, engineers and the rest of these
    I think should be checked by their own committees
    No one should practice contracting unless we can expect
    Good standards will be maintained in the work we’ll get
    Code of ethics should become a part of what they do
    Overlook them and they should be fined and suspended too
    Doctors are monitored by their oath and so we trust
    Even when we’re in doubt, that they are doing as they must

    ————–
    GWP Responds:
    Hi Khaidji:

    That was very good. Please note that Engineers also have a code of ethics that obligates them to inform the relevant authority of safety concerns. In this instance, the home owner is the relevant authority.

    You may appreciate the following poem, written in 1907 by Rudyard Kipling, to describe the great responsibilities of Engineers.

    Regards,
    Grenville

    The Sons of Martha

    The Sons of Mary seldom bother, for they have inherited that good part;
    But the Sons of Martha favour their Mother of the careful soul and troubled heart.
    And because she lost her temper once, and because she was rude to the Lord her Guest,
    Her Sons must wait upon Mary’s Sons, world without end, reprieve, or rest.

    It is their care in all the ages to take the buffet and cushion the shock.
    It is their care that the gear engages; it is their care that the switches lock.
    It is their care that the wheels run truly; it is their care to embark and entrain,
    Tally, transport, and deliver duly the Sons of Mary by land and main.

    They say to mountains, ‘Be ye removed’. They say to the lesser floods, ‘Be dry’.
    Under their rods are the rocks reproved – they are not afraid of that which is high.
    Then do the hill-tops shake to the summit – then is the bed of the deep laid bare,
    That the Sons of Mary may overcome it, pleasantly sleeping and unaware.

    They finger death at their gloves’ end where they piece and repiece the living wires.
    He rears against the gates they tend: they feed him hungry behind their fires.
    Early at dawn, ere men see clear, they stumble into his terrible stall,
    And hale him forth like a haltered steer, and goad and turn him till evenfall.

    To these from birth is Belief forbidden; from these till death is Relief afar.
    They are concerned with matter hidden – under the earthline their altars are;
    The secret fountains to follow up, waters withdrawn to restore to the mouth,
    And gather the floods as in a cup, and pour them again at a city drouth.

    They do not preach that their God will rouse them a little before the nuts work loose.
    They do not teach that His Pity allows them to leave their work when they damn-well choose.
    As in the thronged and the lighted ways, so in the dark and the desert they stand.
    Wary and watchful all their days that their brethren’s days may be long in the land.

    Raise ye the stone or cleave the wood to make a path more fair or flat:
    Lo, it is black already with blood some Son of Martha spilled for that:
    Not as a ladder from earth to Heaven, not as a witness to any creed,
    But simple service simply given to his own king in their common need.

    And the Sons of Mary smile and are blessed – they know the angels are on their side.
    They know in them is the Grace confessed, and for them are the Mercies multiplied.
    They sit at the Feet – they hear the Word – they see how truly the Promise Runs:
    They have cast their burden upon the Lord, and – the Lord He lays it on Martha’s Sons.

    Rudyard Kipling, 1907
    Ref: Luke 10:38-42

  9. Can you offer some advice on which contractors or companies/ builders are actually building according to the code in Barbados? Should a first time home owner get an engineer to design the house instead of an architect?

    ————–
    GWP Responds:
    Hi Slc:

    I am unaware of any builders that comply with the national building code.

    You may need an Engineer if the house falls outside of the Code. The Code is applicable for 1 and 2 storey buildings with an area under the roof of less than 230 sq-m or 2,500 sq ft. (BNBC 2.402.1 (B)(i & ii)). An Engineer does not have to design the house; however, until such time as our Government recognises and assumes its responsibilities to home owners, it would be prudent for a structural Engineer to review the drawings before you build.

    Regards,
    Grenville

  10. Grenville
    What about Lime Grove at Holetown, allegedly built on 100 ft of clay, in fact, on a swamp. Are these buldings going to be safe, and if so, how will they make it safe?

    ————–
    GWP Responds:
    Hi Ian:

    Building on clay can be challenging especially if the clay is not stable. The building can rise of fall depending on the clay’s properties. What we do not want is differential or uneven movement of the building, i.e. tilting.

    If the clay is homogeneous, i.e. uniform properties throughout the site and within the clay layer, then laboratory test results on the clay can allow the designer to predict the movement and design the building accordingly.

    Due to the challenges of building on unstable clays, the Building Code states that an Engineer should design such foundations. (BNBC 2.503.2)

    So to answer your question: The Engineer should design them, and check to see that they are built safely. If a structural Engineer was not involved in their design, then the developer would be well advised to seek such professional advice with dispatch.

    Regards,
    Grenville

  11. Thanks for the info Grenville. Very useful. I must say that the steel anchors are much easier to work with than the method which bajans currently use for the roof.

    Couple of questions for you: I passed by Coverly where government is building houses in JV programmes with the private sector and saw a number of houses being build using a cast in place concrete method. The speed at which these houses are being built seem to be a lot faster than the traditional block method. How does this method compare to the traditional methods of building.

    Also I read in the Business Authority that you believe that houses can be built with luxury finishes for $100/ sq ft. Is this truly possible in this day with labour and material cost being so high?

    ————–
    GWP Responds:
    Hi Novice:

    I will inspect those houses this week and report my findings by updating this response to you.

    UPDATE START/ I visited the Coverly and Emerald City sites. The Emerald City houses are precast building elements connected together. The Coverly houses are reinforced concrete wall and floor panels cast in place. The construction quality is typical./UPDATE END

    I built my house for approximately BD$100 per sq ft using porcelain tiles (albeit 2nd choice), granite counter tops, Purpleheart roof framing and close boarding, Claytone roof tiles, laminated glass windows, 3 m (10’) floor to floor height, and over 30 m (100’) of 460 mm (18”) diameter columns. I was able to do this by:

    1. assuming the role of contractor and therefore not paying for risks;
    2. purchasing principal materials and obtaining the contractor’s discounted prices;
    3. paying my main builder in accordance with his priced bill of qualities.

    In today’s (25 February 2008 ) Barbados Business Authority that you referenced, I have identified a procedure that would allow a potential home owner realise an affordable house. I will link that article here and will also discuss construction costs there. I will prefer to discuss construction quality issues here.

    Regards,
    Grenville

  12. Pingback: Structural Engineer Grenville Phillips Hits Brick Wall «

  13. Saw you site for the first time. Love it. It echoes alot of things I’ve thought about. And I’m not an engineer just a prospective homeowner.

    Thanks James.

    Regards,
    Grenville

  14. UPDATE START/ I visited the Coverly and Emerald City sites. The Emerald City houses are precast building elements connected together. The Coverly houses are reinforced concrete wall and floor panels cast in place. The construction quality is typical./UPDATE END

    Hi Genville, How do the reinforced concrete wall compare in quality to block work construction?

    Hi Novice:

    If the reinforced concrete wall is cured properly, then its strength should exceed that of a concrete block wall. It should also be less vulnerable to lateral forces from earthquakes and hurricanes.

    Regards,
    Grenville

  15. Very informative.Keep up the Fight,Never give up.
    What is the approx cost of a typical foundation per sq ft inclusive of floor ?

    Hi Jackson:

    The foundation is the most uncertain part of building to quantify; principally because the builder does not know how far he has to excavate in order to reach a good bearing stratum (which may or may not be rock). Once the builder has reached the ground floor level, then the construction costs can be calculated with much more certainty.

    Assuming a 1.2 m (4′) depth of excavation, the foundation to ground floor slab can probably be completed in the order of $25 per sq foot.

  16. I have been doing some reading etc., One problem I can see is with the Shear wall. This is one area which can be enforced by the town planning department. It can’t be the fault of the builder if they build following a plan which has been approved by T&CP that has no shear walls in it.

    Hi Novice:

    You are correct. The builder cannot be faulted for complying with T&CP approved drawings. I also cannot fault the builders for much of the substandard construction practises. I really do not believe that they know that their work is substandard. That is why knowledge of building standards is so necessary, and this could have been facilitated by the Chief Town Planner simply specifying a condition of approval that stated that the construction must comply with the Structural Requirements of the BNBC.

    I have trained the planners and inspectors in Grenada how to check applications for building code compliance, and I have offered to do the same in Barbados free of cost. However, to date, no response. I am happy that you can see how simple it really is.

    Regards,
    Grenville

  17. I have been reading all of these articles intently, as i intend to soon start building, and it has been informative…and somewhat daunting.

    Where can a copy of the Building Code be obtained ?

    Hi Soon Building:

    You can obtain a copy of the BNBC from the Barbados National Standards Institution, Culloden Road, St Michael. They cost $100 each. You can call them at 426-3870.

    Since you are planning to build, let me encourage you to check back here in about a week or so. You should not build to the minimum standards of the code, rather you should try to exceed them. Why build the worst thing that the code will allow? I will post some tips on exceeding the minimum building standards at no or very little additional cost.

    Best regards,
    Grenville

  18. Thank you very much for your prompt reply.Again very informative.

    No problem.

    Grenville

  19. Thanks for the info, and i will continue to keep checkin the site. Quite informative.
    Have passed it on to my friends as well.

    Thanks Soon Building:

    Regards,
    Grenville

  20. Is it absolutely necessary to install the plumbing in the foundation? Would’nt it be more cost effective to track the areas where the plumbing is needed : 2 baths ,kitchen ,washroom.Would’nt it relate to a cost saving.

    Hi Jackson:

    The plumbing pipes are normally placed within or directly under the ground floor slab and in the walls. There are three principal reasons for this. First, it allows more direct and therefore shorter pipe runs (lengths). Secondly, it stabilises the pipe joints that tend to move when under pressure. Thirdly, it protects them from damage. The main problem is the potential damage to the floor in the event of a pipe leak.

    I would suggest that the bathroom, kitchen, and washing plumbing fixtures be located near the external walls to minimize any damage to the structure in the event of a leak.

    Regards,
    Grenville

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  22. I just read this post. I see a lot of info pics etc but I dont see anything about concrete slabs and hang floors. I am planning to build this year and I am getting varying views on how floors should be reinforced. Some say put 1/2 ” steel others recomment using wire mesh… What is the correct way?

    Hi Tony:

    The Barbados National Building Code (BNBC) allows both. Section 2.603.2 contains a table that shows you the minimum thickness of concrete slab, and the minimum reinforcement to be used for a given span. I would recommend that you use more than the minimum. It also includes a drawing showing the builder how to position the reinforcement. Section 2.603.3 then provides the builder with slab construction information, like the strength of the concrete.

    The BNBC … don’t build home without it.

    Regards,
    Grenville

  23. I went off and bought the building code. The table is clear but the diagram in section 2.603.3 is not very clear to me. Do you have to put top an bottom reinforcement? Is the top reinforcement only locate where the intermediate walls are? Please see if you can clarify that diagram for me.
    Thanks

    Hi Tony:

    The drawing shows steel reinforcement placed near the bottom of the slab between supporting walls.

    The drawing also shows steel reinforcement placed near the top of the slab over the intermediate support. This “top reinforcement” must extend 1/4 of the span.

    You will notice that the “bottom reinforcement” does not extend to the intermediate support. This is the worst possible practice that the Code will allow. You should allow this reinforcement to extent to the support.

    Regards,
    Grenville

  24. Okay thanks.
    Some people suggest using half inch steel instead of the wire mesh? What are your views on this.

    Hi Tony:

    The minimum building standards in the Code are just that – minimum building standards.

    If it were my house, and I must interrupt myself here so that you may clearly understand that I am not giving you any advice here whatsoever, since I have neither seen the plans of your house, nor received information on your loading requirements. My advice to you would be to exceed the minimum building standards in the Building Code and to seek the advice of a Registered Engineer. That said, I would assume that my wife and I may be entertaining a lot of people on our patio. Therefore for a 3.6 m (12′) span, I would use a 150 mm (6″) thick slab, and 12 mm (1/2″) diameter high yield (also called high tension) reinforcement to the British Standard BS4449. The 12 mm bars would continuously span the supports and be spaced at 150 mm (6″).

    I would use this slab thickness and reinforcement wherever I expect heavier loads, like my library. Where I expect lighter loads, like a bedroom or bathroom, I would keep the 150 mm thick slab but increase the spacing of the reinforcement to 200 mm (8″).

    If I were uncertain about the future use of a space or room, then I would assume patio loading throughout.

    Regards,
    Grenville

  25. I know roofs are very technical and therefore costs run rather high.What is the average cost per sq.ft using corrugated sheet and close boarding (t-111) and is this cheaper compared to a Ceiling using Gypsum board.

    Hi Jackson:

    You can probably have the roof framing and close boarding installed for around $25/sq ft. The Gypsum Wall Board is cheaper than the T-111, however, if it gets wet, it can facilitate mould growth. Please be advised that during a hurricane, if the building envelope is breached, just about everything inside gets wet. Principally for that reason, I would not use the gypsum material.

    Regards,
    Grenville

  26. Pier footings or strip fottings? Is there any advantage of using one over the other? Which one is more cost effective?
    Aren’t the pier footings supposed to be connected by a strip footing??

    Hi Tony:

    Pier footings or pad footings are normally used to economically support columns. Strip footings are normally used to economically support walls.

    Regards,
    Grenville

  27. Are the pad footings supposed to be connected by beams??

    Hi Tony:

    The BNBC 2.506.2 specifies minimum pier or column pad footing sizes and notes that such footings should be continuous.

    It is good practise to tie the pad footings to other footings using tie beams. If it were my house, and I must once again interrupt myself here so that you may clearly understand that I am not giving you any advice here whatsoever, since I have neither seen the plans of your house, nor received information on your loading requirements. My advice to you would be to exceed the minimum building standards in the Building Code and to seek the advice of a Registered Engineer. That said, I would use 200 mm deep x 300 mm wide concrete beams reinforced with minimum 4 x 12 mm diameter high yield bars with 8 mm diameter links spaced 200 mm apart.

    Regards,
    Grenville

  28. I have just started to build and my contractor is saying that I should have 1/2″ steel in every block hole for the foundation wall and that each hole should be poured with concrete. Is this necessary or is it an overkill?

    Hi Novice:

    Of course I must give you the standard preamble as given to Tony W in the post before yours, since I have not seen the site.

    The amount of vertical reinforcement that your builder is using is normal if the wall is to retain something. Perhaps it is to retaining water from an underground water tank, or external soil because the foundations are deep.

    If the foundations are shallow, and there is no soil or water to retain, then if it were my house, I would use 12 mm (1/2″) diameter high yield bars at 600 mm (2′) centres for all of the walls, not just the foundation. It is also important to fill all block cavities below the ground floor slab with grout, even the ones without any reinforcement.

    The BNBC calls for a minimum of 10 mm diameter mild steel reinforcing bars at 800 mm centres. (BNBC 2.405.2 (c))

    Regards,
    Grenville

  29. thanks grenville. the foundations are shallow.

    Ok. You know what to do.

    Regards,
    Grenville

  30. Dear Grenville I have read your article with interest. I am a bajan returnee and have purchased land in Barbados and eager to get started on plans etc. Can you give me any information on how many dollars per square foot it would cost for a three bedroom 2 bathroom house. My land is at St Peters Haywood Estate. Also can you recommend any good builders?
    Regards John

    Hi John:

    For budgetary reasons, you should estimate $250 per square foot of floor area. I regret to report that I cannot in all good conscience recommend any good builders. You will see why in today’s article.

    Regards,
    Grenville

  31. I see you say that it is a violation to fill on the rock and then put the footings on it. Is this still aproblem if the fill is compacted in a satisfactory manner in small lifts. The reason I ask this, is because I read somewhere that when placing the footing on Rock you have to be careful of the jagged edges of the rock as these creste pressure points on the footings resulting in “fractures” or breakages in the footing itself after a period of time. Please do shed some light on this.
    Thanks

    Hi Smoove:

    The Barbados National Building Code (BNBC) states: “Excavations for footings shall be taken down to the depths necessary to provide solid support of the loads superimposed by the building. FOOTINGS SHALL NOT BEAR ON FILL MATERIAL.” BNBC 2.504.4 (Emphasis mine)

    Therefore excavate until you find the necessary solid support. If you do not find it, then you need some professional advice depending on the type of soil that you have (sand, clay, etc)

    Regarding jagged edges of rock. It is good practise to cut into the rock 50 mm to 75 mm to remove the weathered portion, provide a relatively flat bearing area, and provide a key to the footing.

    Regards,
    Grenville

  32. Hi Grenvill, I am preparing to build a single story wall home. The code recommends 16″ wide and 8″ deep minimum footings. Contractor suggests 24″ wide and 10 ” deep footings. Is this an overkill/ waste of money? or should I go with the contractor.

    Hi Smoove:

    The Code (section 2.506.1) actually recommends a minimum strip footing size of 12″ wide x 8″ thick (300 mm x 200 mm) assuming a good bearing material. The 16″ wide x 10″ thick (400 mm x 250 mm) is for a two storey building. You may wish to consider the two storey foundation size since you or your estate may wish to add another storey at a later date.

    The 24″ (600 mm) wide footing exceeds the minimum for rock. If your footings are not bearing on hard limestone, then it may be prudent to use the 24″ wide footing to manage the risk. In my opinion, it is not a waste of money. Perhaps a 36″ (900 mm) wide footing for a single storey house on hard limestone could be a waste of money.

    Regards,
    Grenville

  33. In many houses that are built in Barbados, the area for the footings is excavated and after the foundation walls are built the marl is placed on the mud. Is this practice accceptable or are you supposed to excavaate the entire area to rock?
    thanks

    Hi ASP:

    The Barbados National Building Code, Section 2.507 provides the procedure for concrete slabs on ground floors. You should remove the “top-soil and any organic material” (BNBC 2.507.2 (a)).

    Mud (topsoil and organic material) will compress. If you leave it in, then you can use it as formwork to support your slab, which you should design as a suspended slab. BNBC Section 2.603 gives the minimum thickness and reinforcement requirements for suspended slabs.

    If you wish the underlying material to permanently support the ground floor slab, then you must remove the topsoil and organic material and replace it with granular (e.g. marl) fill.

    Best regards,
    Grenville

  34. Hi Grenville, my house was built 2006-2007 and unfortunately I’m pretty sure from reading your posts that it is not in the best shape to withstand any IVAN like strike… Short of demolishing it and starting over, or running to a shelter in defeat every time I hear a hurricane is threatening, what would you recommend a home owner in my position do improve a house’s chances of surviving a hurricane? From what I can see I have : 1) Not enough sheer walls, 2) Roof rafters spaced at 770mm!!!!! Can these issues be mitigated after the house is completed without having to rob a bank?! (Note: It wasn’t me who was up at the 6X roads RBTT recently … I was working!)

    Hi Wstraughn:

    The Barbados National Building Code (BNBC) allows rafters to be spaced up to 1.2 m, however, you should use the timber type, size, and span as specified in Table 2.803.9. However, if it were my house, I would not space the more than 600 mm apart.

    Let me state that I am not giving you any advice here whatsoever, since I have neither seen the plans of your house, nor received information on your loading requirements. My advice to you would be to exceed the minimum building standards in the Building Code and to seek the advice of a Registered Engineer.

    1. Roof

    The first thing that I would do is to determine whether my roof is actually substandard. If I have a 2.4 m (8 ft) long 2”x6” Purpleheart rafter, then my 770 mm spacing exceeds the minimum requirements of the BNBC. However, a similar rafter out of Pine is less than what the BNBC requires.

    I would install stainless steel hurricane connectors at all timber connections, and ensure that I used stainless steel screws or nails. I would also install rafter bracing (collar tie) and additional roof covering connections as shown in the BNBC Figure 2.805.

    2. Shear Walls

    If my walls are timber stud walls, then I would install a timber brace as shown in Figure 2.804.2. If they are concrete block, then I would fix a 50 mm x 50 mm galvanised weldmesh (BRC Ref.5050 25) to the external face of the widest panels that I had, and apply a 12 mm minimum (1 cement:3 sand) mortar plaster. See BNBC Figure 2.405A for a description of the wall panels.

    3. Windows and Doors

    I would secure my windows and doors. United Insurance has a booklet which describes some effective retrofitting measures and which can be downloaded from here:
    http://www.unitedinsure.com/united.cfm?LID=helpful%20info&SID=Hurricane%20Retrofitting

    I would also get adequate insurance.

    Regards,
    Grenville

  35. What is your opinion of using ESP (Extruded Foam Panels) as a building option in Bds?

    Hi Ray:

    ESP is not normally a structural (load bearing) material. It can be used as insulation sandwiched between structural materials.

    However, given the improvements in building materials, if a manufacturer has been able to develop a structural foam panel, then you should request the technical specifications, and ensure that it comes with a verifiable warrantee if you wish to use it.

    If you know of such a manufacturer, then you are welcome to post its web-site here so that it can be Weighed in the Balance.

    Regards,
    Grenville

  36. Pingback: The Worst House that the Code Will Allow « Weighed in the Balance

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  38. Wow talk about poor quality and lack of inspections. These guys need to be held to some codes.

    Hi Mike:

    The difficult obstacle appears to be the will to do, rather than any knowledge deficiencies.

    Regards,
    Grenville

  39. Pingback: Power back on near Grape Hall, Barbados. What a mess! « Barbados Free Press

  40. Hi my name is Felix Oliver my email address is fusoconstruction@gmail.com can u send your contact info? You are someone I can speak to in connection with my business. Thank you.

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