Wee deck project

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chevrolux

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#1765324 17-Apr-2017 15:03

neb:
Willuknight:

So I'm going to build a small extension to my deck to house a spa pool.

I've never built a deck before,

So just a general comment, what's your building knowledge and skills like? This seems rather more complex than just concreting in some piles and laying a deck on them, which means you'd need at least some experience and specialised knowledge on how to do it. You really need to use the correct tool for the job for something like this, and for this sort of job I'd say the correct tool to apply is a builder. It looks like the sort of thing that a standard builder would do as a side-job over a weekend or two, which could save you a lot of headaches in terms of getting all the details right.

Where's the fun in that though?

Boeingflyer

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#1765357 17-Apr-2017 16:41

chevrolux:
neb:
Willuknight:

So I'm going to build a small extension to my deck to house a spa pool.

I've never built a deck before,

So just a general comment, what's your building knowledge and skills like? This seems rather more complex than just concreting in some piles and laying a deck on them, which means you'd need at least some experience and specialised knowledge on how to do it. You really need to use the correct tool for the job for something like this, and for this sort of job I'd say the correct tool to apply is a builder. It looks like the sort of thing that a standard builder would do as a side-job over a weekend or two, which could save you a lot of headaches in terms of getting all the details right.

Where's the fun in that though?

Give it a go, it's fun and you learn heaps. If you stuff it up, whats the worst thats going to happen, rip it all back up. From what i see, it's not bearing any load apart from walking on it, nothing else special about it. Just give it ago and have some fun, you'll find swear words become quite common but at the end you can have a beer and tell your mates about it.

Willuknight

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#1766449 17-Apr-2017 23:20

Yup - I'm pretty confident I can pull it off. I have pretty much all the tools I need to get the job done - for the most part, and a bunch of DIY experience / can do attitude. I've also read all the guides and they mostly make sense. The stringers and packing it out will be easy, so no worry about me attaching it directly to the house.

The one thing I wasn't sure, my drill is a ryobi impact drill, will this do the job of drilling out the bolt holes for the bearers and joists?

Also can someone tell me how you would normally attach a joist to a bearer? It looks like you need extra hardware if you're going to do the joist sitting on top of the bearer, and therefore it would be cheaper to build it so the joist is fastened into the bearer.

For example, in the image, on the right the joists are sitting on top, which would require brackets to attach to the bearer? VS on the right, the joists are just bolted/screwed into the bearers on both sides.

People keep on talking about H5 for piles - I actually want to avoid using piles in the ground, my plan was to sink a concrete block into the ground, fill it with gravel and morter and then bolt a masonry pile anchor on to the top - that way they piles doesn't even have to come near the ground.

Disrespective>

For the joists, stringer and bearers, the guides I checked suggested 150x50 so that's what I'm currently planning on, 140x90 seems structurally overkill for the scope of the project? It's not even 1m wide. I can get H4 wood for $8/m so I was probably going to go with that, do you think it will be ok? Total deck size (bit at back, left to right is 650mm wide by 2060mm.

Disrespective

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#1766654 18-Apr-2017 11:50

140x45 is the same as 150x50. Regardless, a bearer is what carries the joists load between piles. This member needs to be larger than the individual joists and its size is determined using the loaded dimension. Generally this is the distance between the piles, but if only spanning between two piles anyway, then it's half this distance. If your bearer spans 2m between piles/support then the L.D is 1m, but using Table 6.4 from NZS3604 you have to use the loaded dimension of 1.2m (even though you are less, this is the minimum option they provide) and this shows a size of 140x90 as the recommended bearer size.

Bear in mind that if you had the deflection determined by an engineer then this may be less. YMMV.

There are many different ways to transfer the bearer load into the ground. You don't have to use piles that are set into a concrete footing, they're simply the easiest. All piles purchased from merchants (bunnings/mitre 10 etc) will be H5 treated anyway. And to be honest, i'd say easier to deal with than a bearer bracket, but that's just my experience.

You can check the MiTek site for examples of how you need to install the timber connections. eg. http://www.mii.com/artefact/download.asp?aid=65744 These detailed info sheets are also found with most of the products on the shelves of the merchants if you want to see one in person.

mdf

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#1766670 18-Apr-2017 12:29

Willuknight:

The one thing I wasn't sure, my drill is a ryobi impact drill, will this do the job of drilling out the bolt holes for the bearers and joists?

A hammer drill? You will need a masonry bit and a hammer drill to drill into concrete. It's hard work going into concrete; I always use a corded drill for this. A battery drill that has a hammer action should work, but it will probably be slow going (you'll want to rest and let it cool down between holes) and might use most of a charge per hole. It is easier if the drill has an auxiliary/second handle too - you will have more control and can exert a bit more force. Most battery drills don't.

Also can someone tell me how you would normally attach a joist to a bearer? It looks like you need extra hardware if you're going to do the joist sitting on top of the bearer, and therefore it would be cheaper to build it so the joist is fastened into the bearer.

For example, in the image, on the right the joists are sitting on top, which would require brackets to attach to the bearer? VS on the right, the joists are just bolted/screwed into the bearers on both sides.

If you've got the clearance, it's better to have the joist sitting on top of the bearer (your left hand image). You can then just skew nail it to the bearer (dwang it to stop it twisting). This way the bearer is actually bearing the load. If you hang your joist off your bearer (a ladder frame style construction), the only thing holding it up is the strength of the screws/nails - and these don't hold particularly well in the end grain. You actually need additional hardware for this style of construction - a joist hanger.

People keep on talking about H5 for piles - I actually want to avoid using piles in the ground, my plan was to sink a concrete block into the ground, fill it with gravel and morter and then bolt a masonry pile anchor on to the top - that way they piles doesn't even have to come near the ground.

This should work, but seems like a lot of work and expense compared to a short wee pre-cut pile and a bag of fastcrete (about $10 each). I find it easier to get everything level by digging out the holes and then nailing the piles to the bearers. You can then hang the piles off the bearers in the holes and manually prop everything up level with spare timber (I've been known to use car jacks for this too). Then backfill the holes with the concrete, let it set and you're done.

You will also find yourself limited in the amount of height you can get with the masonry block approach, vs. buying whatever length pile you need.

For the joists, stringer and bearers, the guides I checked suggested 150x50 so that's what I'm currently planning on, 140x90 seems structurally overkill for the scope of the project? It's not even 1m wide. I can get H4 wood for $8/m so I was probably going to go with that, do you think it will be ok? Total deck size (bit at back, left to right is 650mm wide by 2060mm.

I will start by repeating that I am not a builder and so anything I have to say may well not meet the requirements of any part of the building code. Don't rely on anything I have to say. Especially if you are building anything that requires consent.

But the approach I take is that basically a certain amount of wood is required to make things structurally sound. Within reason, you can play around with this a bit. If you want to use a smaller/thinner bearer, you need more piles. Smaller joists = more bearers etc. So for example, one project required a deck that only had 200mm clearance to the ground. Ideally I would have dug the ground out 100mm+ to allow 300mm for 150 + 150 bearers plus joists. But nuts to that. Instead I put in a lot more piles and used 100mm joists and bearers (I can't recall the figures, but I would have used in the order of twice as many piles and bearers than I would have for 150mm). It was still an overall massive time and effort saving compared to the earthworks that would have been required otherwise.

The Carters' guide is my bible for deck framing. Using it's suggested spans, something like this would work well for you I think:

This is only 4 posts to dig out, and no stringers to worry about.

Personally, I'd probably use a third bearer in the middle. 2m joist spans are about the max for 150x50. Even then, you should be able to do six holes pretty quickly. You need one-third to half the pile in the ground (I do more but I build *solid*). Adjust the pile lengths and amount of concrete to suit the height of your deck.

EDIT: Clarity

mdf

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#1766672 18-Apr-2017 12:35

And actually, thinking about it, how many steps are you doing? You will normally need a pile in each corner of each step. So two steps = six piles, three steps = 8 piles, four steps = 10 piles etc. 200mm is about the maximum rise for an even vaguely comfortable step.

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