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Civil Engineering/Load weight question: Deck

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Expert: - 2/13/2005


Question
We built a new deck onto our house one year ago with the intention of adding a hot tub in one corner. Here are the dimensions (its a large one):
30 feet in length, 15 feet wide and about 15ft tall.
We used 8x8's for the posts (rather than 4x4's) and we added an extra 8X8 about 4 feet out from the corner where we thought we would want the hot tub. For joists, we doubled up 2X12's. The hot tub would weigh about 4,000 pounds, or about 75lbs per square foot.
Are we ok, before I have them crane this thing onto it? Thanks for your time.

Answer
Hi Matt,

I had replied earlier, but seems it did not get to you.

I regret I cannot design over this forum for insurance plus other reasons. However, timber is easy to check for design capacity by doing a simple load test. Just put some drums or jerry can in the bath location and slowly fill with water of up to 4000lbs weight + weight of occupants. Check the deflection of the deck and if it's below span/250, you are OK. OR if you hear some creaking sound from the timber well before than you know you ahve a problem.

I hope that helps!

Kind rehards,

Arshad  

Civil Engineering

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Arshad Khan

Expertise

I can answer any questions to do with civil and structural engineering consultancy and construction industry in East Africa and the Middle East, and specifically with the analysis and design of reinforced concrete structures. My particular expertise is in the aseismic design and optimisation of tall buildings.

Experience

Employment history: 36 years in Construction and consultancy in the UK, Kenya, Tanzania, Uganda, Ethiopia, Eritrea, South Africa, Somalia, Zambia, Austria, Bahrain, Kuwait, Doha and the U.A.E.

Organizations
.Fellow of Institution of Structural Engineers (UK) .Fellow of Institution of Civil Engineers(UK) .Member of the Institution of Engineers, Kenya .Registered Engineer, ERB, Kenya .Member of the Architectural Association of Kenya (Engineers Chapter) .Chartered Engineer (UK)

Publications
•1984: International Conference on the Art and Practice of Structural Design, London •1994: 3rd Int. Kerensky Conference in Structural Engineering, Singapore •2008: International Conference on High-Rise Towers, Abu Dhabi

Education/Credentials
BSc, 1st Class Hons, in Building Engineering, University of Bath, UK MSc in Concrete Structures and Technology, University of London. Diploma of Imperial College, UK.

Awards and Honors
•Science Congress Special Award (for 2-seater Hovercraft - 1968) •Institution of Civil Engineers Award for outstanding performance at Bath University (1975) •Concrete Society Postgraduate study Bursary Award (1976) •Consular Representative for British High Commission, Nairobi. (1995 to 1998) •Examiner for Institution of Civil Engineers Professional Interviews, Nairobi. (1997 to 1998) •Branch Representative in Vienna for PI assessment for Inst. of Struct. Engrs. (1999 to date)

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