Mark Leverton
Hi Mike Yes I would remove the stumps or get someone to grind them down for you. I would certainly sit your deck on concrete blocks as it will keep the timber off the damp. Also put down a weed suppressive membrane under the whole deck.Do not put the summerhouse on the deck because when the deck rots, ( and it will) you will have to re situate your house. Put the summerhouse on a concrete base and deck around it . Hope this Helps Mark Surrey Hills Landscaping