11
15 Most common deck construction mistakes Matt Shutkowski © Copyright 2012 15 MOST COMMON DECK CONSTRUCTION MISTAKES Feb, 2012 Mistakes to avoid The 15 most common mistakes are easy to avoid, we look at the main causes for these mistakes and how to avoid them. Matt Shutkowski

15 Most Common Deck Construction Mistakes

Embed Size (px)

Citation preview

Page 1: 15 Most Common Deck Construction Mistakes

15 Most common deck construction mistakes

Matt Shutkowski © Copyright 2012

15 MOST COMMON DECK CONSTRUCTION MISTAKES

Feb, 2012 Mistakes to avoid

The 15 most common mistakes are easy to avoid, we look at the

main causes for these mistakes and how to avoid them.

Matt Shutkowski

Page 2: 15 Most Common Deck Construction Mistakes

15 Most common deck construction mistakes

Matt Shutkowski © Copyright 2012

FOOTINGS

#1- Hitting underground water, power and/or gas mains

The consequences of hitting a water, power and/or gas main have the potential for serious to fatally

injuring you! Not to mention the inconvenience of not having no power or water. So to avoid this

unnecessary and dangerous frustration, do all your checks with your local government agency and

service providers (call “Dial before you dig” on 1100 in Australia). Once you have the locations for the

services, mark them out on the ground when you mark out your footing locations so as not to hit them

when you dig your footings.

When you dig you footings it is highly recommended that you dig them by hand with a shovel and

crow bar. This way if you are unfortunate enough to hit one, you have more chance of not seriously

damaging the service.

Something to keep in mind, if you hit a water, power and/or gas main and you have spoken to “Dial

before you dig” and have done as much as possible for locating the mains, you will greatly minimise

your liability.

#2 – Timber posts rotting away within a few years of the deck being

completed

There can be many reasons for this, the most common are as follows:

i- Timber posts that are concreted directly into the concrete footing.

This is a problem because concrete is porous and absorbs ground moisture. This has the

timber post be continually moist, the perfect environment for timber rot. The post will rot in

the location shown below the quickest, as it is the last place to dry out and the first place

to get wet.

Concrete

footing Timber

post

Where the rot

most occurs

in timber

posts

Page 3: 15 Most Common Deck Construction Mistakes

15 Most common deck construction mistakes

Matt Shutkowski © Copyright 2012

ii- Timber posts having gardens or dirt/soil built up around them and/or touching the timber

post will cause the post to rot. Below is a picture of a timber post that has rotted away

because of soil build up.

To solve this problem the best way is to install galvanised stirrups into domed concrete footings where

the base of the timber post is raised 75mm above the top of the domed concrete. This also allows for

any water to run off the top of the concrete footing which greatly aids in the life of the galvanised

stirrup (a stirrup is a metal bracket that holds the timber post out of the concrete).

75mm gap between the

domed concrete and

timber post

Domed concrete

Hot dipped galvanised

steel stirrup

Page 4: 15 Most Common Deck Construction Mistakes

15 Most common deck construction mistakes

Matt Shutkowski © Copyright 2012

#3 - Sinking deck frames

The most common reason is incorrect footing size, normally due to not having an engineer design the

structural components of the deck. Any other reason is the owner bolts the deck posts directly to an

existing concrete slab that is untested, usually a pathway. Most concrete paths over 20years old do

not have any form of concrete/steel reinforcing.

The best and only recommended way to install deck posts is directly into dug footings using galvanised

steel stirrups making sure the footing hole is dug straight down and not what is called in the industry

“belled”.

SUBFLOOR FRAMING

#4 – Deck floor sagging

99% of the time this is due to incorrect timber/timber size being used. If you have an engineer design

your deck you will not have this problem. The two main types of timber is softwood (all types of pines,

etc) and hardwood, as you can imagine just by the name one is stronger than the other. You can swap

softwood with a hardwood and not have a problem keeping in mind that you must use structurally

rated timber. However if you go the other way, swaping hardwood for a softwood (usually done in

an attempt to save money) you will have major problems if not a collapsed deck.

The sides of

the hole are

curved and

rounded

Belled hole

The sides of the

hole are straight

and flat giving a

square shape

Square hole

Page 5: 15 Most Common Deck Construction Mistakes

15 Most common deck construction mistakes

Matt Shutkowski © Copyright 2012

#5 – Timber cracking and breaking

Aside from swapping hardwoods for softwoods as mentioned in the above problem, this is most

commonly caused by too much timber cut out of the joins. The maximum amount of timber that can be

cut out of a joint is 1/3 of the height, width or thickness. There are a few ways this can be measured:

When more than 1/3 of the timber height, width or thickness needs to be cut out additional support

needs to be added. This can be in the form of metal brackets.

A hole can only be a

maximum of 1/3 the

height of the joist.

Joist

1/3 max

Bearer

Joist Here you can see in red

less than 1/3 of the timber

in the joists height has been

left to sit on top of the

bearer.

This is where the timber will

crack and break due to the

little amount of timber

sitting on top of the bearer.

More than 1/3 – Not OK

Less than 1/3 - OK

Bearer

Joist Here you can see in

red over 2/3 of the

timber in the joists

height has been left to

sit on top of the bearer.

Page 6: 15 Most Common Deck Construction Mistakes

15 Most common deck construction mistakes

Matt Shutkowski © Copyright 2012

#6 – Bolts, nails and steel rusting

USE GALVANISED BOLTS, NAILS AND STEEL!!!!!!

This is not optional. You will have your deck start to fall apart in a matter of months if you do not use

galvanised bolts, nails and steel. Galvanising is where zinc coats the steel, usually done by dipping the

steel into a molten vat of zinc. Zinc as a metal is more corrosive than steel, so when steel is coated in

zinc the zinc will corrode before the steel corrodes. This in turn will leave your steel corrosion free for

a very long time.

DECKING

#7 – Black and other marks on decking boards

The black marks are caused by leaving metal on a wet deck. The only way to stop this from

happening, is to clean the deck after each day of construction. Pick up all tools, nails, bolts and

anything else metal and sweep the deck down. When you nail in nails there is a small amount of metal

filings that fall off the nail when hammering it in. Finially do not use a grinder on the deck or

anywhere near the deck or where people will walk on to the deck. Grinding sparks leave metal filings

everywhere and as you will see in the pictures below leave a very ugly mark.

Galvanised bolt

versus a non-

galvanised bolt

A non-galvanised

steel beam. Make

note of the amount

of rust that has

occurred.

Page 7: 15 Most Common Deck Construction Mistakes

15 Most common deck construction mistakes

Matt Shutkowski © Copyright 2012

There is a couple of ways to remove these black marks however it will take a lot of elbow grease:

Option one- Clean the deck with a product called “Deck clean” (a mild acid) and scrub like you have

never scrubbed before;

Option two- Sand the marks out, best to do this by hand as power sanders can end up making more of

a mess than the black mark itself.

Grinding

sparks

Bolt &

nail marks

Bracket

mark

Page 8: 15 Most Common Deck Construction Mistakes

15 Most common deck construction mistakes

Matt Shutkowski © Copyright 2012

#8 – Decking boards not installed to a straight line

There are many ways to install your decking boards in a straight line. The easiest way to do this is to

use a chalk line (a chalk line is a string line coated in chalk that when you flick it leaves a straight line

of chalk) and mark out every forth/fifth board (called a grid board) and completely nail that board

to every floor joist. Once you have installed all the grid boards, place all the other boards in between

them and use wedges to evenly space the boards between the grid boards. Make sure when you do

this that you allow a 2-3mm gap between each board.

#9 – Greying and rotten of decking boards

This can be caused by not coating the deck with a decking oil or stain once the deck was complete. This

is also caused from not maintaining the decking oil or stain in years to come. If your deck is does not

have a roof over it, the sun will deteriorate the coating faster than a covered deck. A good rule of

thumb, is that the moment any of the coating is starting to fade or look grey it is time to re-coat the

deck.

Grid

board

Grid

board

Page 9: 15 Most Common Deck Construction Mistakes

15 Most common deck construction mistakes

Matt Shutkowski © Copyright 2012

ROOF FRAME, ROOFING & CEILINGS

#10 – Losing your deck roof in a severe storm

To avoid this you need to engage an engineer to design all structural aspects of your deck. This is not

a recommendation, this is a must. If you build your deck without the appropriate engineering and

something goes wrong, you are liable. If someone gets hurt you can be charged with assault etc.

#11 – Leaking roofs

The most common and sometimes not the most obvious reason is that the roof screws have been over

tightened. The roof screw has a rubber washer at the base of the head of the screw. This washer

seals the hole that the roof screw has made in the roof sheet when screwed. When the screw has been

over tightened it squashes the rubber washer and breaks it, allowing water to enter into the screw

hole. See below.

#12 – Sagging ceiling

The most common reason is the ceiling supports are positioned to far apart. Once the ceiling is

installed, the ceiling maybe flat and straight. However over time usually in about 6 months moisture in

the air will soften the ceil enough for gravity to start to sag the ceiling sheets causing a wave like

effect on the ceiling.

Rubber washer

Screw tighten correctly where you

can see the intact rubber washer

Screw over tighten where you can

see the rubber washer has broken

away from the screw

Page 10: 15 Most Common Deck Construction Mistakes

15 Most common deck construction mistakes

Matt Shutkowski © Copyright 2012

STAIRS & HANDRAILS

#13 – Out of level stairs

When the stair set height is measured, called the “rise” (height from ground to top of decking boards)

this has been measured straight down from the edge of the deck however not where the stairs meet the

ground, called the “run” (distance from edge of decking board to front edge of bottom step tread). In

the diagram below you can see the height difference between straight down from the edge of the

deck compared to where the stairs actually meet the ground. If rise height is measured close to the

deck and not where the stairs meet the ground in you will have too many/not enough step treads

required for your set of stairs. This will result in your step treads either tilt forward or backwards.

Deck

Post

Ground

Rise

Run

Page 11: 15 Most Common Deck Construction Mistakes

15 Most common deck construction mistakes

Matt Shutkowski © Copyright 2012

#14 – Stairs handrails to low

Firstly if you don’t know what the minimum height of handrails are, check with your local building

authority or engineer. The top of the handrail is measured straight up and down from the top front

edge of the step tread which is called the “nosing line”. The nosing line is an imaginary line that runs

along the top front edge of every step tread. This is where your local government agency will

measure your handrail from, to check that the handrail meets building regulations.

THE BIGGEST MISTAKE MADE

#15 – local government agency having the deck changed or removed

This is a very easy mistake to avoid, get your deck approved before building it. If you choose to try

and do it without the correct approvals this can end up costing far more than just local government

agencies fees saved. The local government agency may not have you remove the deck, they may just

want you to change the size or even location of the deck. As you can imagine this is going to be a

major re-work for your deck.

Deck

Nosing Line, always measure

to the top of your handrail to

this line.

Handrail

Where you measure

your handrail from