Want to build a deck

[khusnil_deo]

Hi there,

I have an alfresco that I wish to deck out. The alfresco is concreted with the house if that makes sense. Now I have compiled a list as below to take on this projec.

1. a concrete sealer to prevent moisture coming out of the concrete slab.

2. H3 treated 90x45 pine for joists and bearers.

3. Merbau decking 19mm height in the 90mm width.

4. stainless steel decking screws.

5. joist hanger.

6. fixings to fix the joist to the concrete slab.

7. spacers 4mm

8. multitool counter sink drill bit

9. decking oil

now i am having some issues with my concrete slab. the alfresco is a permanent part of the house and is undercover, but having said that, when it rains, there is a slight gush of rain which wets a part of the alfresco (east facing). Now the problem is that my alfresco has a 70mm setdown, there's weep holes just above the very first course of bricks so I prefer not to cover it as it may void the builder's warranty. so now i have a total of just 70mm height to build my deck.

I have narrowed down that I will need to lay the joist flat side up meaning i will have a 45mm height of the joist instead of the 90mm height, then i will use the bracket (Carinya 50x50x40x3.5mm) and position the joist in such a way that there is a 5mm clerance between the concrete slab and the joist. in theory this will give me a 45mm height of joist and 5mm clearance and 19mm height of merbau decking, sufficient to work with a 70mm setdown.

Is there a better way of increasing this clearance? i don't like the idea of the joist sitting in direct contact with the concrete slab thereby shortening the life of my joist and bearers? i have considered the plastic window packers but i have reached a dead end. Can someone please help. I want to do the decking by this weekend and want to order the materials from the green shed.

thank you.

[Jason]

Hi @khusnil_deo,

Can you please share some photos of the area so that members can get a better idea of what you are working with?

Many thanks,

Jason

[EricL]

Hello @khusnil_deo

Thank you for sharing your proposed idea for building a deck. Let me try and answer some of your questions. 

• If the weep holes in your wall are not covered or sealed by the deck frame. The weep holes should still function effectively. You can build your frame with a provision for the weep holes. This will allow you to build past the weep holes.
• I don't recommend building your frame with the joist flat side up. This will compromise the strength of the joist and you will end up with a spongy or bouncy deck. The joist is strongest with the narrow side up.

Would it be possible for you to post your framing plan and your proposed decking area? This will allow our members to see how you plan on building your decking frame. We can then offer you advice and information. Can you also please tell us the gap between your door and the concrete slab.

If you need further assistance, please let us know.

Eric

[khusnil_deo]

[khusnil_deo]

Dear @EricL ,

I have uploaded pictures of my alfresco and patio that I wish to deck. You can see the weep holes above the first course of bricks which I don't want to muck around with for warranty purposes as its a new build. Please also excuse the mess. The setdown is 70mm and that is the height I have to work with. So in theory, I have 35mm height timber framing, with about 15mm of ground clearance and 19mm Merbau decking. That is if I use the flat side up of the 90X35mm or 70X35mm. I can't think of any other framing system. I will use the window plastic packers to achieve the clearance. What are your thoughts?

[khusnil_deo]

Since i have only 70mm height to work with, what size joist do i use?

[Jason]

@khusnil_deo,

@EricL will be back on the site this afternoon to assist. Let me tag @Adam_W for his thoughts in the meantime as I understand you are keen to get started. 

Thanks,

Jason

[khusnil_deo]

Thank you @Jason. Yes I am very keen to get started. I just want the joist and clearance issue resolved so that I can start ordering things from Bunnings. Thank you again. Enjoy your morning

[EricL]

Hello @khusnil_deo

Thank you so much for posting those photos. Let us for the moment consider that we can build over the weep holes. How much space would you be able to use then? At the moment 70mm is not enough space to build a solid timber frame. If we take away the thickness of the decking panel which is 19mm you would be left with 51mm neither the 70mm nor 90mm timber framing will work. A possible option would be to use a metal frame, but you would have to engage the services of an engineer as they would be familiar with the use of the material.

If you place a timber buffer in front of your timber frame so that the weep holes are not covered it will still allow them to function as intended. The weep hole's purpose is to allow air to circulate in the brick wall. This is to prevent moisture from getting trapped inside your wall. As long as they are open and uncovered air will still be able to enter in and out of them.

If you need further assistance, please let us know.

Eric

[khusnil_deo]

Dear @EricL ,

thank you so much for reply to my post. Unfortunately I still have that 70mm height to work with to make the deck flush with the brick work just where the entrance to the alfresco sliding door is. In the front patio I can make it flush with the door jamb but the finish will not look nice without the picture frame. I have seen people use the flat most part of either the 90X45 or 90X35 and they use packers underneath it. they just have to make sure that the space between each joist is closer than the recommended 45cm. and they waterproof the joist by applying bitumen paint.

I really want this deck as I have put so much effort and time in sourcing the materials and teaching myself how to build a deck.  My husband even bought a circular saw and I trained myself how to mitre cut to achieve the picture framing finish to this deck. Pretty please. Once again, I am stuck with the 70mm height.