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Background - Existing pavers are 7 x 1.5 m. (which is about 2 steps down from sliding door) and garden at the sliding door level - which is about 400mm above the pavers level. Existing pavers are down because of the ventilation issues under the home. It is very odd, going down and up again to go to garden – and pavers are really looking bad – weeds are growing too.
Now, planning to build deck on existing pavers - with increased size of 7 x 2.5 m - additional 1 mtr would be float on top of existing grass (as seen in pic) – happy to dig some soil to provide proper look and ventilation for the deck.
Need help plan this job. Potential issues:
- slightly concerned about building deck / over ventilation points- would it hinder the structure ventilation – gap in slats is good enough for vent purposes? anything I could do to make sure that the house subfloor gets enough air – without compromising the idea of decking?
- how to effectively collect storm water from garden / and join to stormwater collection pit – that it doesn’t damage the deck.
- not sure how the joining of garden and deck works - any suggestion? - retaining wall ? - pls share pic if possible
- suggestion for footings material and positions to go on top of both pavers and grass
- deck and support structure quantity
- if someone has effectively done this type of job – pls advice on your experiences. - thanks in advance for any advice / tips for this newbie DIYer
Welcome to the Bunnings Workshop community @diy_ujjaval. It's fantastic to have you join us and many thanks for your questions.
If you intend to have the deck flush with the door sill that will mean it is significantly higher than the pavers. If the deck is left open at the sides I don't think ventilation would be adversely affected. You might like to consider Bradford EcoFan White Sub Floor Ventilator - 2 Pack if you are concerned with this issue.
You could dig down and install Vinidex draincoil agricultural drainage parallel to the house to prevent water coming from the garden and entering under the deck. This drainage pipe can be directed to the pit.
If you start the deck flush with the door sill and run it out onto the lawn area it will be above the height of the soil. I don't believe a retaining wall would be needed in that case.
I've included a brief design of an example layout for your deck utilising Treated Pine Outdoor Timber Framing 140 x 45mm as the bearers and Treated Pine Outdoor Timber Framing 90 x 45mm as the joists. You'll need to use a mixture of supports for the bearers given the height differences.
You should find this step-by-step tutorial helpful: Planning to build a deck. You might also like to read through @Adam_W's guide: How to build a low-level deck.
Please let me know if you need further assistance or have any questions.
Mitchell
Thank you Mitchell 
for the response - much appreciated.
1. with regards to supports - do i need to take out the pavers n install (concrete) the support ? or I can just let the support / alternative to supports to sit on top of the pavers (not necessarily be concreted)?
2. How do I practically make sure the deck is leveled? - do I need any tool / techniques - I watched the 5 video series on decking but that technique doesn't apply for floor decking. - any suggestion / reference here - how to level the deck when laying support/bearers/joists?
3. the bit i m not sure about is how the finish / edges of the deck from the garden looks? - Is it on the grass level ? - allowing snail and other insects to climb over the deck / do you have any reference video or pics that I can replicate on my job? -
4. Also I liked your idea on running AG line around the deck borders where garden touches - do you have any reference for how to lay AG line - and how finished product probably look - i understand the slope part, but good to get some easy / practical reference that I can replicate in my job. Again Thank you.
5. There is a small pargola structure above existing pavers - and there are 3 existing support / where pargola is attached to. It is at very convenient location - can I utilize the same support for decking as well - how do I attach / what items do I need for bearers to connect with the existing support where pargola is sitting (not intending to remove pargola here)- to be used as decking support? Can you suggest attachments - thanks. - the pic was attached in the original post.
6. Material selection - in decking sitting closer to the ground - is treated pine - prone to rotting ?
Thanks in advance.
Ujjaval
Hi @diy_ujjaval,
1. It would be best practise to take out pavers and install the supports into concrete footers. The pavers can sink under the additional weight and therefore the whole deck might subside.
2. We have a whole range of levelling devices to assist you with the project. You might be interested in investing in a 360-degree laser level like the Ozito 360° 20m Line Laser Level Plus Tripod which would be super useful.
3. I've included a couple of picture below of finishing the edges of the deck. You can bring it down flush with the grass or leave it exposed if you don't want the contact. If you don't want insect and grubs crawling up onto it you should finish it above the grass line.
4. You should find this step-by-step tutorial helpful: How To Build Retaining Wall. It includes a section on installing drainage pipe. You might also be interested in checking out: EVERHARD EasyDRAIN Installation Instruction Video.
5. You can fix the deck to the existing pergola structure. You should not rely on it solely for support unless you are aware of how the posts are fixed into the ground. You can use galvanised bolts to attach bearer to the post for additional support of the structure.
6. The bearers for the deck will be H3 treated pine timber which is suitable for exterior above ground use. If the timber is in contact or close proximity to soil H4 timber should be used. Alternatively, you can remove soil to keep it further away from the H3 timber.
Please let me know if you have further questions.
Mitchell
